JP2021008781A - Roof base material and roof structure provided with the same - Google Patents

Abstract

To prevent the decay of a field board in a roof base material having the field board and a roof structure provided with it.SOLUTION: There is provided a roof structure 1 of a building including a roofing material 10, a roof base material 20 to which the roofing material 10 is attached upward, and a heat insulating material 30 provided below the roof base material 20, in which a field board 21 is composed of a medium density fiberboard having a density of 0.7 or more and less than 0.85 and a water absorption rate of 15% or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a roof base material and a roof structure including the roof base material.

Conventionally, a roof base material having a field board and a waterproof sheet spread on the upper surface of the field board has been used (see, for example, Patent Document 1 below).

Patent Document 1 discloses a roof structure in which a heat insulating material is provided parallel to the field plate below the field plate of the roof base material. In addition, in this roof structure, ventilation passages that communicate with the outside are formed at two places between the field board and the heat insulating material so that the moisture generated indoors in winter and reaching the back of the hut is discharged to the outside. .. In the above roof structure, by providing such a ventilation path, moisture generated indoors in winter reaches the back of the cabin, causing dew condensation between the tarpaulin and the field board, and the field board is prevented from decaying. It is preventing.

Japanese Unexamined Patent Publication No. 4-293834

However, in the roof structure, the discharge of moisture depends on the inflow amount (wind speed) of the outside air from the back of the eaves. Therefore, in a windless state, moisture may be insufficiently discharged even if a ventilation path is provided, dew condensation may occur on the back surface of the field board, and the field board may rot.

Further, in the above roof structure, rainwater that has entered through the gaps between the roofing materials may reach the inside of the field board through the nail holes of the nails that penetrate the waterproof sheet and the field board. Structural plywood, which has been conventionally used as a field board, has a high water absorption rate, and such rainwater easily permeates. On the other hand, in the above roof structure, since the field board is covered with a waterproof sheet, there is also a problem that the field board infiltrated with rainwater is difficult to dry and easily decays.

The present invention has been made in view of such a point, and an object of the present invention is to prevent decay of a field board in a roof base material having a field board and a roof structure provided with the same.

In order to achieve the above object, in the present invention, in the roof base material having a field board, a medium density fiberboard having a water absorption rate of 15% or less is used as the field board.

Specifically, the first invention is a roof base material provided with a field board and a roofing material is attached upward, and the field board has a density of 0.7 or more and less than 0.85 and a water absorption rate of 15. It is characterized in that it is composed of a medium density fiberboard of% or less.

Here, the water absorption rate is determined by measuring the weight (m1) of the test piece that has reached a constant weight in an environment of a relative humidity of 65 ± 5%, and then placing the test piece in water at 20 ± 1 ° C. and immersing it for 24 hours. After that, the test piece was taken out and a water absorption rate test was performed to measure the weight (m2), and it was calculated from the weight difference of the test piece before and after water immersion measured in the water absorption test (weight of the test piece before and after water immersion). It is the value obtained by dividing the difference (m2-m1) by the weight m1 before water immersion and multiplying it by 100).

In the first invention, the field board is composed of a medium density fiberboard (MDF: Medium Density Fiberboard) for structure having a density of 0.7 or more and less than 0.85. Medium density fiberboard is a wood board formed by heat-pressing wood fibers together with an adhesive to form a board, and since gaps are formed between the wood fibers, it has been conventionally used as a field board. Moisture permeability resistance is lower than that of plywood. Therefore, according to the roof base material provided with a field board that easily allows moisture to permeate, even if the humidity generated indoors in winter reaches the back of the cabin, it can be discharged to the outside through the field board. , Moisture does not accumulate on the back side of the field board. Therefore, it is possible to suppress the occurrence of dew condensation on the back surface of the field board and the decay of the field board without providing a ventilation path.

Further, according to the first invention, a medium density fiberboard having a water absorption rate of 15% or less is used as a field board. Such a field board is less likely to absorb rainwater adhering to the surface than a conventional field board (water absorption rate of 60% or more) made of structural plywood or the like. In addition, according to such a field board, even in the place where the nail is driven, the wood fiber coated with the adhesive adheres to the nail driven so as to separate the wood fibers, and rainwater enters the nail hole. It becomes difficult for water such as water to enter. By using a medium density fiberboard with excellent waterproofness that is hard to absorb water not only from the surface but also from the nail holes as a field board, even if rainwater reaches the roof base material through the gaps in the roofing material, rainwater will be compared to the conventional one. Is much harder to penetrate into the field board, and it is possible to suppress the decay of the field board. Further, even if rainwater permeates the field board, it does not reach the back surface of the field board, so that it is possible to prevent rain leakage.

That is, in the first invention, in the roof base material having a field board, a medium density fiberboard having an excellent moisture permeability and waterproof property and a water absorption rate of 15% or less is used as the field board to prevent the field board from decaying. be able to.

In the second invention, in the first invention, the medium density fiberboard is composed of a urea-melamine cocondensation resin-based adhesive, a first adhesive composed of at least one of diphenylmethane diisocyanate and a phenol resin, and a urea resin-based adhesive. It is characterized by containing a second adhesive made of an adhesive.

In the second invention, as an adhesive for a medium density fiberboard constituting a field board, a first adhesive comprising at least one of a urea-melamine cocondensation resin adhesive having excellent water resistance, diphenylmethane diisocyanate and a phenol resin. Is used. In such a medium density fiberboard containing the first adhesive, the wood fibers are coated with the first adhesive, so that it becomes difficult for water to penetrate between the wood fibers and the water absorption rate becomes low. On the other hand, if the medium density fiberboard is formed using only the first adhesive having excellent water resistance as an adhesive, the water absorption rate can be remarkably reduced, but the moisture permeation resistance may increase. Further, since the first adhesive having excellent water resistance is expensive, if only the first adhesive is used as the adhesive, the medium density fiberboard also becomes expensive, and the manufacturing cost of the roof base material increases. Therefore, in the second invention, it is decided to use a medium density fiberboard using a second adhesive made of a urea resin-based adhesive which is inexpensive and has low water resistance as an adhesive together with the first adhesive. Since the second adhesive is inexpensive and has low water resistance, it is possible to obtain a medium density fiberboard having a water absorption rate of 15% or less at a relatively low cost by using it in combination with the first adhesive, which is expensive and has high water resistance. It can be formed without increasing the moisture permeation resistance. Therefore, by using such a medium density fiberboard as a field board, it is possible to easily and relatively inexpensively provide a roof base material having a field board having excellent moisture permeability and waterproofness.

The third invention is characterized in that, in the second invention, the medium density fiberboard has a moisture permeation resistance of less than 2.5 m ² · h · mmHg / g.

Here, the moisture permeation resistance is a value measured in accordance with the cup method specified in JIS A1324.

In the third invention, a medium density fiberboard having a moisture permeation resistance of less than 2.5 m ² · h · mmHg / g is used as a field board. By using the medium density fiberboard having extremely low moisture permeation resistance and excellent moisture permeability as the field board, the effect of suppressing the occurrence of dew condensation on the back surface of the field board and the decay of the field board is further increased.

A fourth invention is characterized in that, in any one of the first to third inventions, a moisture permeable waterproof sheet provided on the upper surface of the field board is provided.

In the fourth invention, a moisture permeable waterproof sheet is provided on the upper surface of the field board. That is, a sheet having further moisture permeability and waterproofness is provided on the upper surface of the field board having excellent moisture permeability and waterproofness. With such a configuration, the waterproof property of the roof base material is further improved, so that the decay of the field board can be further suppressed.

A fifth invention is a roof structure of a building including a roofing material, a roofing material to which the roofing material is attached upward, and a heat insulating material provided below the roofing material, wherein the roofing material is provided. Is a roof base material according to any one of the first to fourth inventions.

In the fifth invention, the above-mentioned roof base material having a roofing material, a roof base material, and a heat insulating material, which has a field board which is excellent in breathability and waterproofness and is hard to decay, is used. By using such a roof base material, it is possible to suppress the occurrence of dew condensation on the back surface of the field board and the decay of the field board without providing a ventilation path between the roof base material and the heat insulating material. Therefore, by using the roof base material, a roof structure that does not easily decay can be easily constructed without a ventilation path, and can be easily constructed.

As described above, according to the roof base material of the present invention and the roof structure provided with the same, since the medium density fiberboard having a water absorption rate of 15% or less is used as the field board, it is possible to prevent the field board from decaying. it can. Further, even if rainwater permeates the field board, it does not reach the back surface of the field board, so that it is possible to prevent rain leakage.

FIG. 1 is a cross-sectional view showing a part of the roof structure of the building according to the first embodiment. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. FIG. 3 is a schematic view showing a state of the water permeability test. FIG. 4 shows the test results of the water permeability test.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are essentially preferred examples and are not intended to limit the scope of the invention, its applications, or its uses.

<< Embodiment 1 of the invention >>
As shown in FIGS. 1 and 2, the roof structure 1 is a so-called roof heat insulating type roof structure, and includes a roofing material 10, a roof base material 20, and a heat insulating material 30. The roofing material 10 and the roof base material 20 are constructed above a plurality of rafters 2, ..., 2 arranged at intervals in the hut structure of the building. The heat insulating material 30 is provided between each of the plurality of rafters 2, ..., 2. A gypsum board 3 is attached to the lower end surfaces of the plurality of rafters 2, ..., 2.

In the first embodiment, the roofing material 10 is made of clay roof tiles. The roofing material 10 is fixed to the tile rail 11 attached to the roof base material 20. The roofing material 10 is attached to the roof tile 11 with nails 4 driven toward the roof tile 11. The roofing material 10 is not limited to the viscous roof tile, and may be a cement roof tile, a slate, a metal plate, or the like, but a clay roof tile or a cement roof tile having good breathability is preferable.

The roof base material 20 is attached to a plurality of rafters 2, ..., 2. A plurality of roof tiles 11, ..., 11 extending in the girder direction are attached to the upper surface of the roof base material 20. The plurality of roof tiles 11, ..., 11 are fixed by nails 5 driven toward the rafters 2. The detailed configuration of the roof base material 20 will be described later.

The heat insulating material 30 is made of rock wool. The heat insulating material 30 may be any material as long as it has a heat insulating effect, and for example, a fiber-based heat insulating material such as glass wool can be used. In the first embodiment, the heat insulating material 30 is provided directly under the roof base material 20.

With the above configuration, in the first embodiment, the roof structure 1 is configured as a so-called roof heat insulating type roof structure in which the heat insulating material 30 is provided not on the ceiling side but on the roof side.

<Detailed composition of roof base material>
The roof base material 20 includes a field board 21 and a moisture-permeable waterproof sheet 22. Both the field board 21 and the moisture-permeable waterproof sheet 22 have both moisture permeability and waterproofness. Therefore, in the first embodiment, a communication passage communicating with the outside is not provided between the heat insulating material 30 and the field board 21.

[Field board]
The field board 21 is composed of a medium density fiberboard (MDF: Medium Density Fiberboard) for a structure having a density (g / cm ³ ) of 0.7 or more and less than 0.85. In this embodiment, a medium density fiberboard having a density of 0.79 g / cm ^{3 and} a thickness of 9.2 mm is used as the field board 21.

The medium density fiberboard constituting the field board 21 contains a first adhesive having excellent water resistance and a second adhesive having lower water resistance as compared with the first adhesive. In the first embodiment, the field board 21 is composed of a medium density fiberboard containing a urea-melamine cocondensate resin adhesive as a first adhesive and a urea resin adhesive as a second adhesive. Further, in the first embodiment, in the field board 21, the first adhesive and the second adhesive are blended so that the weight ratio is the first adhesive: the second adhesive = 2: 8. Has been included. The first adhesive is not limited to the urea-melamine co-condensation resin adhesive, and may contain at least one of a urea-melamine co-condensation resin adhesive, diphenylmethane diisocyanate, and a phenol resin.

(Water absorption rate)
The field board 21 is configured so that the water absorption rate is 15% or less. The field board 21 is preferably configured so that the water absorption rate is 13.6% or less, and more preferably the water absorption rate is 13.2% or less.

Here, the water absorption rate is determined by measuring the weight (m1) of the test piece that has reached a constant weight in an environment of a relative humidity of 65 ± 5%, and then placing the test piece in water at 20 ± 1 ° C. and immersing it for 24 hours. After that, the test piece was taken out and a water absorption rate test was performed to measure the weight (m2), and it was calculated from the weight difference of the test piece before and after water immersion measured in the water absorption test (weight of the test piece before and after water immersion). The difference (m2-m1) divided by the weight m1 before water immersion multiplied by 100) is used.

As described above, in the medium density fiberboard containing the first adhesive having excellent water resistance, the wood fibers are coated with the first adhesive, so that it becomes difficult for water to penetrate between the wood fibers and the water absorption rate becomes high. It gets lower. Therefore, by using the first adhesive for molding the medium density fiberboard constituting the field board 21 and adjusting the blending ratio thereof, the water absorption rate of the field board 21 can be adjusted to the desired water absorption rate, that is, 15 in the present embodiment. % Or less (preferably 13.6% or less, more preferably 13.2% or less).

The water absorption rate test was performed on the structural plywood A (sugi) and the structural plywood B (surface layer larch, core layer sugi) having a thickness of 12 mm, which were conventionally used as field boards, and the water absorption rate was calculated. The water absorption rates were 82% and 61%. From this, it can be seen that the water absorption rate of the field board 21 of the first embodiment is remarkably low as compared with the conventional field board.

(Moisture permeability)
The field board 21 is configured such that the moisture permeation resistance measured in accordance with the cup method specified in JIS A1324 is less than 2.5 m ² · h · mmHg / g.

As described above, the medium density fiberboard containing the first adhesive having excellent water resistance has a low water absorption rate. On the other hand, if the medium density fiberboard is formed using only the first adhesive having excellent water resistance as an adhesive, the water absorption rate can be remarkably reduced, but the moisture permeation resistance may increase.

However, in the first embodiment, a second adhesive made of a urea resin-based adhesive, which is inexpensive and has low water resistance, is used as an adhesive together with the first adhesive for molding the medium density fiberboard constituting the field board 21. I am using it. Since the second adhesive has lower water resistance than the first adhesive, medium density fibers having a low water absorption rate (15% or less) can be used in combination with the first adhesive having high water resistance. The board can be formed without increasing the moisture permeation resistance. That is, by adjusting the blending ratio of the first adhesive and the second adhesive, the field board 21 having a water absorption rate of 15% or less and a moisture permeation resistance of less than 2.5 m ² · h · mm Hg / g. Can be configured. In the first embodiment, as described above, the weight ratio of the first adhesive made of the urea-melamine cocondensation resin adhesive and the second adhesive made of the urea resin adhesive is second. Adhesive of 1: 2 Adhesive = 2: 8 By using a medium density fiberboard formed by blending and adding as a field board 21, the water absorption rate is 15% or less and the moisture permeation resistance. The field board 21 having a thickness of less than 2.5 m ² · h · mm Hg / g can be formed.

As for the structural plywood A and structural plywood B which has been conventionally used as a sheathing roof board, moisture permeation resistance, as measured in accordance with a cup method prescribed in JIS A1324 ^is a 23m 2 · h · mmHg / g 27m was ² · h · mmHg / g. From this, it can be seen that the moisture permeation resistance of the field plate 21 of the first embodiment is remarkably low as compared with the conventional field plate, that is, the moisture permeation performance is remarkably high.

[Moisture permeable waterproof sheet]
The moisture permeable waterproof sheet 22 is configured so that the moisture permeable resistance measured in accordance with the cup method specified in JIS A1324 is 0.65 m ² · s · Pa / μg or less. This moisture permeation resistance complies with the regulations of the moisture permeation waterproof sheet for roofs of JIS A6111. In the first embodiment, the moisture permeable waterproof sheet 22 is made of a resin film provided with a large number of micropores (diameter: about 0.5 μm), and has a moisture permeability resistance of 0.5 m ² · s · Pa / μg or less. It is configured. The moisture permeable waterproof sheet 22 may be any material as long as it conforms to JIS A6111, or may be made of a non-woven fabric. Further, these may be laminated.

<Waterproofness of field board>
As described above, since the water absorption rate of the field board (structural plywood) is high in the conventional roof base material, rainwater that reaches the field board through the nail hole penetrating the waterproof sheet penetrates from the surface of the field board to the inside. It was easy. In addition, with conventional roof base materials, the water blocking property of the nail holes that penetrate the field board is low, and when rainwater reaches the field board, it penetrates into the nail holes of the field board, and rainwater is absorbed inside the field board from the nail holes as well. Was there. That is, in the conventional roof base material, the water permeability of the field board is high, and the field board is liable to decay.

On the other hand, in the roof base material 20 of the first embodiment, since the water absorption rate of the field board 21 is low (15% or less), rainwater that reaches the field board 21 through the nail hole of the nail 5 penetrating the moisture permeable waterproof sheet 22. Is difficult to penetrate from the surface of the field board 21 to the inside. Further, in the roof base material 20 of the first embodiment, since the water blocking property of the nail hole is high, it is difficult for rainwater to leak from the nail hole, and since it is difficult for rainwater to enter the nail hole, rainwater is hard to enter from the nail hole. It is not absorbed by 21. That is, in the roof base material of the first embodiment, the water permeability of the field board 21 is low, and the field board 21 is unlikely to decay.

In order to demonstrate this point, the following water permeability test was conducted.

(1) Test bodies Two of the following two types of test bodies X were prepared.

I: Medium density fiberboard (thickness 9 mm, density 0.79 g / cm ³ , moisture content 8.9%)
II: Plywood (thickness 9 mm, density 0.42 g / cm ³ , moisture content 10.6%, softwood)
The test piece X of I is configured so that the water absorption rate is 15% or less and the moisture permeation resistance is less than 2.5 m ² · h · mmHg / g, similarly to the medium density fiberboard constituting the field board 21. Has been done.

(2) Test method First, as shown in FIG. 3, a test instrument is assembled. Specifically, a nail 51 (N50, screw nail) is driven into the center of the test body X from above. A nail 51 of N50 is driven into one of the test bodies X of I (referred to as test body X1), and a screw nail is driven into the other (referred to as test body X2). A nail 51 of N50 is driven into one of the test bodies X of II (referred to as test body X3), and a screw nail is driven into the other (referred to as test body X4). For each of the four types of test bodies X1 to X4 formed in this way, a cylinder 52 (inner diameter 34 mm, height 300 mm) made of acrylic resin is placed upright on the upper surface of the test body X so as to cover the nail 51. After filling the gap between the cylinder 52 and the upper surface of the test body X with the coking agent 53, these are placed on a beaker 54 having a diameter larger than that of the cylinder 52.

After assembling the test equipment, water (normal temperature) is gently poured into the cylinder 52. Water is poured to a position of 250 mm (about 227 ml) in height of the cylinder 52. Then, these were allowed to stand for 8 days in an environment of a temperature of 20 ° C. and a relative humidity of 65%, and the remaining amount of water, the appearance state of the test body X, and the leakage of water from the nail hole were regularly confirmed.

(3) Test Results The graph in FIG. 4 shows the results of the water permeability test. The amount of water permeation (ml) shown on the vertical axis of the graph of FIG. 4 is the amount of decrease in water poured into the cylinder 52. Further, the ■ mark indicates the test body X1, the ◆ mark indicates the test body X2, the ● mark indicates the test body X3, and the ▲ mark indicates the water permeation amount of the test body X4.

As can be seen from the graph of FIG. 4, among the four types of test bodies X1 to X4, the water permeation amount of the test body X4 is the largest, and the water in the cylinder 52 is almost exhausted on the third day after the start of the test, and the test can be continued. It became impossible. Next, the amount of water permeated by the test body X3 was large, and on the 4th day after the start of the test, the water in the cylinder 52 almost disappeared, making it impossible to continue the test. From this result, in the test bodies X3 and X4, a large nail hole is formed when the nail 51 is driven, so that water spreads (penetrates) in the fiber direction of the test body X from the nail hole and the nail 51 is pushed. It can be seen that it easily passes through the lower part of the test body X (beaker 54) (the water-stopping property of the nail hole is low).

On the other hand, the test bodies X1 and X2 constituting the field plate 21 of the first embodiment have a significantly smaller water permeation amount than the test bodies X3 and X4 among the four types of test bodies X1 to X4, and from the start of the test. Even after 3 days, almost no water flowed out from the inside of the cylinder 52. In the test bodies X1 and X2, water did not drip from the nail 51 to the beaker 54 even after 8 days from the start of the test. This is because in the test specimens X1 and X2, the nail 51 is driven so as to separate the wood fibers, and the wood fibers coated with the adhesive adhere to the nail 51, so that a gap through which water passes is hardly formed. It is presumed that this is due to this. Further, the test body X1 is formed of an adhesive containing a first adhesive having excellent water resistance (in the first embodiment, a urea-melamine cocondensate resin adhesive), and has a water absorption rate of 15% or less. ing. Therefore, even if a gap is formed around the nail 51 by the nail hole, it is presumed that water does not infiltrate because the wood fiber is coated with the first adhesive having excellent water resistance. As described above, in the test bodies X1 and X2, water does not permeate into the inside from the surface (upper surface) and does not penetrate into the nail hole, and the water permeability is significantly lower than that of the test bodies X3 and X4, that is, It can be seen that the waterproof property is extremely high.

-Effect of Embodiment 1-
According to the first embodiment, the field board 21 is composed of a structural medium density fiberboard having a density of 0.7 or more and less than 0.85. Medium density fiberboard is a wood board formed by heat-pressing wood fibers together with an adhesive to form a board, and since gaps are formed between the wood fibers, it has been conventionally used as a field board. Moisture permeability resistance is lower than that of plywood. Therefore, according to the roof base material 20 provided with the field board 21 that easily allows moisture to permeate, even if the humidity generated indoors in winter reaches the back of the cabin, it can permeate the field board 21 and be discharged to the outside. Therefore, moisture does not accumulate on the back surface of the field board 21. Therefore, it is possible to suppress the occurrence of dew condensation on the back surface of the field board 21 and the decay of the field board 21 without providing a ventilation path.

Further, according to the first embodiment, a medium density fiberboard having a water absorption rate of 15% or less is used as the field board 21. Such a field board 21 is less likely to absorb rainwater adhering to the surface than a conventional field board (water absorption rate of 60% or more) made of structural plywood or the like. Further, according to such a field board 21, even at the place where the nail 5 is driven, the wood fiber coated with the adhesive adheres to the nail 5 driven so as to separate the wood fibers, thereby causing the nail. Moisture such as rainwater does not easily enter the holes. By using a medium density fiberboard with excellent waterproofness that does not easily absorb water not only from the surface but also from the nail holes as the field board 21, even if rainwater reaches the roof base material 20 through the gaps in the roofing material 10, it has been conventionally used. In comparison, rainwater is much less likely to permeate the field board 21, and the decay of the field board 21 can be suppressed. Further, even if rainwater permeates the field board 21, it does not reach the back surface, and rain leakage can be prevented.

That is, in the first embodiment, in the roof base material 20 having the field board 21, a medium density fiberboard having an excellent moisture permeability and waterproof property and a water absorption rate of 15% or less is used as the field board 21 to obtain the field board 21. It can prevent decay.

Further, in the first embodiment, as the adhesive for the medium density fiberboard constituting the field board 21, the first type is composed of at least one of a urea-melamine cocondensation resin adhesive having excellent water resistance, diphenylmethane diisocyanate and a phenol resin. Adhesive is used. In such a medium density fiberboard containing the first adhesive, the wood fibers are coated with the first adhesive, so that it becomes difficult for water to penetrate between the wood fibers and the water absorption rate becomes low. On the other hand, if the medium density fiberboard is formed using only the first adhesive having excellent water resistance as an adhesive, the water absorption rate can be remarkably reduced, but the moisture permeation resistance may increase. Further, since the first adhesive having excellent water resistance as described above is expensive, if only the first adhesive is used as the adhesive, the medium density fiberboard also becomes expensive, and the manufacturing cost of the roof base material 20 is high. Is bulky. Therefore, in the first embodiment, it was decided to use a medium density fiberboard using a second adhesive made of a urea resin-based adhesive, which is inexpensive and has low water resistance, as an adhesive together with the first adhesive. Since the second adhesive is inexpensive and has low water resistance, it is possible to obtain a medium density fiberboard having a water absorption rate of 15% or less at a relatively low cost by using it in combination with the first adhesive, which is expensive and has high water resistance. It can be formed without increasing the moisture permeation resistance. Therefore, by using such a medium density fiberboard as the field board 21, it is possible to easily and relatively inexpensively provide the roof base material 20 having the field board 21 having excellent moisture permeability and waterproofness.

Also used in the first embodiment, the density fiberboard in the moisture permeation resistance is configured to be less than 2.5m ² · h · mmHg / g as the sheathing roof board 21. By using the medium density fiberboard having extremely low moisture permeation resistance and excellent moisture permeability as the field board 21, the effect of suppressing the occurrence of dew condensation on the back surface of the field board 21 and the decay of the field board 21 is further increased. To do.

Further, in the first embodiment, the moisture permeable waterproof sheet 22 is provided on the upper surface of the field board 21. That is, a sheet having further moisture permeability and waterproofness is provided on the upper surface of the field plate 21 having excellent moisture permeability and waterproofness. With such a configuration, the waterproof property of the roof base material 20 is further improved, so that the decay of the field board 21 can be further suppressed.

Further, according to the first embodiment, the roof structure 1 provided with the roofing material 10, the roof base material 20, and the heat insulating material 30 has the above-mentioned roof having a field board 21 having excellent moisture permeability and waterproofness and being resistant to decay. The base material 20 is used. By using such a roof base material 20, even if a ventilation path is not provided between the roof base material 20 and the heat insulating material 30, dew condensation on the back surface of the field plate 21 and decay of the field plate 21 are suppressed. be able to. Therefore, by using the roof base material 20, the roof structure 1 that does not easily decay can be easily constructed without a ventilation path, and can be easily constructed.

<< Other Embodiments >>
In the first embodiment, the roof base material 20 is composed of the field board 21 and the moisture permeable waterproof sheet 22, but the roof base material 20 may not include the moisture permeable waterproof sheet 22. As described above, since the field board 21 has lower water permeability and is excellent in waterproofness as compared with the conventional field board, it suppresses rainwater from penetrating into the field board 21 even if the moisture permeable waterproof sheet 22 is not provided. Therefore, it is possible to suppress the decay of the field board 21.

Further, in the first embodiment, an example in which the roof base material 20 according to the present invention is applied to the roof structure 1 of the roof heat insulating type has been described, but the roof base material 20 is not on the roof side but on the ceiling side. Of course, it is also possible to apply it to the ceiling insulation type roof structure provided with. Even when applied to a ceiling insulation type roof structure, the same effect as that of the first embodiment can be obtained.

The present invention is useful for roof base materials and roof structures including them.

1 Roof structure
10 Roofing material
20 Roof base material
21 Field board
22 Breathable waterproof sheet
30 insulation

The present invention relates to a roof base material and a roof structure including the roof base material.

Conventionally, a roof base material having a field board and a waterproof sheet spread on the upper surface of the field board has been used (see, for example, Patent Document 1 below).

Patent Document 1 discloses a roof structure in which a heat insulating material is provided parallel to the field plate below the field plate of the roof base material. In addition, in this roof structure, ventilation passages that communicate with the outside are formed at two places between the field board and the heat insulating material so that the moisture generated indoors in winter and reaching the back of the hut is discharged to the outside. .. In the above roof structure, by providing such a ventilation path, moisture generated indoors in winter reaches the back of the cabin, causing dew condensation between the tarpaulin and the field board, and the field board is prevented from decaying. It is preventing.

Japanese Unexamined Patent Publication No. 4-293834

However, in the roof structure, the discharge of moisture depends on the inflow amount (wind speed) of the outside air from the back of the eaves. Therefore, in a windless state, moisture may be insufficiently discharged even if a ventilation path is provided, dew condensation may occur on the back surface of the field board, and the field board may rot.

Further, in the above roof structure, rainwater that has entered through the gaps between the roofing materials may reach the inside of the field board through the nail holes of the nails that penetrate the waterproof sheet and the field board. Structural plywood, which has been conventionally used as a field board, has a high water absorption rate, and such rainwater easily permeates. On the other hand, in the above roof structure, since the field board is covered with a waterproof sheet, there is also a problem that the field board infiltrated with rainwater is difficult to dry and easily decays.

The present invention has been made in view of such a point, and an object of the present invention is to prevent decay of a field board in a roof base material having a field board and a roof structure provided with the same.

In order to achieve the above object, in the present invention, in the roof base material having a field board, a medium density fiberboard having a water absorption rate of 15% or less is used as the field board.

Specifically, the first invention is a roof base material provided with a field board and a roofing material is attached upward, and the field board has a density of 0.7 or more and less than 0.85 and a water absorption rate of 15. It is characterized in that it is composed of a medium density fiberboard of% or less.

Here, the water absorption rate is determined by measuring the weight (m1) of the test piece that has reached a constant weight in an environment of a relative humidity of 65 ± 5%, and then placing the test piece in water at 20 ± 1 ° C. and immersing it for 24 hours. After that, the test piece was taken out and a water absorption rate test was performed to measure the weight (m2), and it was calculated from the weight difference of the test piece before and after water immersion measured in the water absorption test (weight of the test piece before and after water immersion). It is the value obtained by dividing the difference (m2-m1) by the weight m1 before water immersion and multiplying it by 100).

In the first invention, the field board is composed of a medium density fiberboard (MDF: Medium Density Fiberboard) for structure having a density of 0.7 or more and less than 0.85. Medium density fiberboard is a wood board formed by heat-pressing wood fibers together with an adhesive to form a board, and since gaps are formed between the wood fibers, it has been conventionally used as a field board. Moisture permeability resistance is lower than that of plywood. Therefore, according to the roof base material provided with a field board that easily allows moisture to permeate, even if the humidity generated indoors in winter reaches the back of the cabin, it can be discharged to the outside through the field board. , Moisture does not accumulate on the back side of the field board. Therefore, it is possible to suppress the occurrence of dew condensation on the back surface of the field board and the decay of the field board without providing a ventilation path.

Further, according to the first invention, a medium density fiberboard having a water absorption rate of 15% or less is used as a field board. Such a field board is less likely to absorb rainwater adhering to the surface than a conventional field board (water absorption rate of 60% or more) made of structural plywood or the like. In addition, according to such a field board, even in the place where the nail is driven, the wood fiber coated with the adhesive adheres to the nail driven so as to separate the wood fibers, and rainwater enters the nail hole. It becomes difficult for water such as water to enter. By using a medium density fiberboard with excellent waterproofness that is hard to absorb water not only from the surface but also from the nail holes as a field board, even if rainwater reaches the roof base material through the gaps in the roofing material, rainwater will be compared to the conventional one. Is much harder to penetrate into the field board, and it is possible to suppress the decay of the field board. Further, even if rainwater permeates the field board, it does not reach the back surface of the field board, so that it is possible to prevent rain leakage.

That is, in the first invention, in the roof base material having a field board, a medium density fiberboard having an excellent moisture permeability and waterproof property and a water absorption rate of 15% or less is used as the field board to prevent the field board from decaying. be able to.

In the first invention, in addition to the above features, the medium density fiberboard is bonded to a first adhesive composed of at least one of a urea-melamine cocondensation resin adhesive, a diphenylmethane diisocyanate and a phenol resin, and a urea resin adhesive. It is characterized by containing a second adhesive composed of an agent.

In the first invention, as an adhesive for a medium density fiberboard constituting a field board, a first adhesive comprising at least one of a urea-melamine cocondensation resin adhesive having excellent water resistance, diphenylmethane diisocyanate and a phenol resin. Is used. In such a medium density fiberboard containing the first adhesive, the wood fibers are coated with the first adhesive, so that it becomes difficult for water to penetrate between the wood fibers and the water absorption rate becomes low. On the other hand, if the medium density fiberboard is formed using only the first adhesive having excellent water resistance as an adhesive, the water absorption rate can be remarkably reduced, but the moisture permeation resistance may increase. Further, since the first adhesive having excellent water resistance is expensive, if only the first adhesive is used as the adhesive, the medium density fiberboard also becomes expensive, and the manufacturing cost of the roof base material increases. Therefore, in the first invention, it is decided to use a medium density fiberboard using a second adhesive made of a urea resin-based adhesive which is inexpensive and has low water resistance as an adhesive together with the first adhesive. Since the second adhesive is inexpensive and has low water resistance, it is possible to obtain a medium density fiberboard having a water absorption rate of 15% or less at a relatively low cost by using it in combination with the first adhesive, which is expensive and has high water resistance. It can be formed without increasing the moisture permeation resistance. Therefore, by using such a medium density fiberboard as a field board, it is possible to easily and relatively inexpensively provide a roof base material having a field board having excellent moisture permeability and waterproofness.

In the first invention, in addition to the above characteristics, the medium density fiberboard has a water absorption rate of 15% or less and transparency by adjusting the blending ratio of the first adhesive and the second adhesive. It is characterized in that it is configured so that the wet resistance is less than 2.5 m ² · h · mmHg / g.

Here, the moisture permeation resistance is a value measured in accordance with the cup method specified in JIS A1324.

In the first invention, a medium density fiberboard having a moisture permeation resistance of less than 2.5 m ² · h · mmHg / g is used as a field board. By using the medium density fiberboard having extremely low moisture permeation resistance and excellent moisture permeability as the field board, the effect of suppressing the occurrence of dew condensation on the back surface of the field board and the decay of the field board is further increased.

The second invention is characterized in that, in the first invention, the moisture permeable and waterproof sheet provided on the upper surface of the field board is provided.

In the second invention, a moisture permeable waterproof sheet is provided on the upper surface of the field board. That is, a sheet having further moisture permeability and waterproofness is provided on the upper surface of the field board having excellent moisture permeability and waterproofness. With such a configuration, the waterproof property of the roof base material is further improved, so that the decay of the field board can be further suppressed.

A third invention is a roof structure of a building including a roofing material, a roofing material to which the roofing material is attached upward, and a heat insulating material provided below the roofing material, wherein the roofing material is provided. Is a roof base material according to the first or second invention.

In the third invention, the above-mentioned roof base material having a roofing material, a roof base material, and a heat insulating material, which has an excellent moisture permeability and waterproof property and a field board which is hard to decay, is used. By using such a roof base material, it is possible to suppress the occurrence of dew condensation on the back surface of the field board and the decay of the field board without providing a ventilation path between the roof base material and the heat insulating material. Therefore, by using the roof base material, a roof structure that does not easily decay can be easily constructed without a ventilation path, and can be easily constructed.

As described above, according to the roof base material of the present invention and the roof structure provided with the same, since the medium density fiberboard having a water absorption rate of 15% or less is used as the field board, it is possible to prevent the field board from decaying. it can. Further, even if rainwater permeates the field board, it does not reach the back surface of the field board, so that it is possible to prevent rain leakage.

FIG. 1 is a cross-sectional view showing a part of the roof structure of the building according to the first embodiment. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. FIG. 3 is a schematic view showing a state of the water permeability test. FIG. 4 shows the test results of the water permeability test.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are essentially preferred examples and are not intended to limit the scope of the invention, its applications, or its uses.

<< Embodiment 1 of the invention >>
As shown in FIGS. 1 and 2, the roof structure 1 is a so-called roof heat insulating type roof structure, and includes a roofing material 10, a roof base material 20, and a heat insulating material 30. The roofing material 10 and the roof base material 20 are constructed above a plurality of rafters 2, ..., 2 arranged at intervals in the hut structure of the building. The heat insulating material 30 is provided between each of the plurality of rafters 2, ..., 2. A gypsum board 3 is attached to the lower end surfaces of the plurality of rafters 2, ..., 2.

In the first embodiment, the roofing material 10 is made of clay roof tiles. The roofing material 10 is fixed to the tile rail 11 attached to the roof base material 20. The roofing material 10 is attached to the roof tile 11 with nails 4 driven toward the roof tile 11. The roofing material 10 is not limited to the viscous roof tile, and may be a cement roof tile, a slate, a metal plate, or the like, but a clay roof tile or a cement roof tile having good breathability is preferable.

The roof base material 20 is attached to a plurality of rafters 2, ..., 2. A plurality of roof tiles 11, ..., 11 extending in the girder direction are attached to the upper surface of the roof base material 20. The plurality of roof tiles 11, ..., 11 are fixed by nails 5 driven toward the rafters 2. The detailed configuration of the roof base material 20 will be described later.

The heat insulating material 30 is made of rock wool. The heat insulating material 30 may be any material as long as it has a heat insulating effect, and for example, a fiber-based heat insulating material such as glass wool can be used. In the first embodiment, the heat insulating material 30 is provided directly under the roof base material 20.

With the above configuration, in the first embodiment, the roof structure 1 is configured as a so-called roof heat insulating type roof structure in which the heat insulating material 30 is provided not on the ceiling side but on the roof side.

<Detailed composition of roof base material>
The roof base material 20 includes a field board 21 and a moisture-permeable waterproof sheet 22. Both the field board 21 and the moisture-permeable waterproof sheet 22 have both moisture permeability and waterproofness. Therefore, in the first embodiment, a communication passage communicating with the outside is not provided between the heat insulating material 30 and the field board 21.

[Field board]
The field board 21 is composed of a medium density fiberboard (MDF: Medium Density Fiberboard) for a structure having a density (g / cm ³ ) of 0.7 or more and less than 0.85. In this embodiment, a medium density fiberboard having a density of 0.79 g / cm ^{3 and} a thickness of 9.2 mm is used as the field board 21.

The medium density fiberboard constituting the field board 21 contains a first adhesive having excellent water resistance and a second adhesive having lower water resistance as compared with the first adhesive. In the first embodiment, the field board 21 is composed of a medium density fiberboard containing a urea-melamine cocondensate resin adhesive as a first adhesive and a urea resin adhesive as a second adhesive. Further, in the first embodiment, in the field board 21, the first adhesive and the second adhesive are blended so that the weight ratio is the first adhesive: the second adhesive = 2: 8. Has been included. The first adhesive is not limited to the urea-melamine co-condensation resin adhesive, and may contain at least one of a urea-melamine co-condensation resin adhesive, diphenylmethane diisocyanate, and a phenol resin.

(Water absorption rate)
The field board 21 is configured so that the water absorption rate is 15% or less. The field board 21 is preferably configured so that the water absorption rate is 13.6% or less, and more preferably the water absorption rate is 13.2% or less.

Here, the water absorption rate is determined by measuring the weight (m1) of the test piece that has reached a constant weight in an environment of a relative humidity of 65 ± 5%, and then placing the test piece in water at 20 ± 1 ° C. and immersing it for 24 hours. After that, the test piece was taken out and a water absorption rate test was performed to measure the weight (m2), and it was calculated from the weight difference of the test piece before and after water immersion measured in the water absorption test (weight of the test piece before and after water immersion). The difference (m2-m1) divided by the weight m1 before water immersion multiplied by 100) is used.

As described above, in the medium density fiberboard containing the first adhesive having excellent water resistance, the wood fibers are coated with the first adhesive, so that it becomes difficult for water to penetrate between the wood fibers and the water absorption rate becomes high. It gets lower. Therefore, by using the first adhesive for molding the medium density fiberboard constituting the field board 21 and adjusting the blending ratio thereof, the water absorption rate of the field board 21 can be adjusted to the desired water absorption rate, that is, 15 in the present embodiment. % Or less (preferably 13.6% or less, more preferably 13.2% or less).

The water absorption rate test was performed on the structural plywood A (sugi) and the structural plywood B (surface layer larch, core layer sugi) having a thickness of 12 mm, which were conventionally used as field boards, and the water absorption rate was calculated. The water absorption rates were 82% and 61%. From this, it can be seen that the water absorption rate of the field board 21 of the first embodiment is remarkably low as compared with the conventional field board.

(Moisture permeability)
The field board 21 is configured such that the moisture permeation resistance measured in accordance with the cup method specified in JIS A1324 is less than 2.5 m ² · h · mmHg / g.

As described above, the medium density fiberboard containing the first adhesive having excellent water resistance has a low water absorption rate. On the other hand, if the medium density fiberboard is formed using only the first adhesive having excellent water resistance as an adhesive, the water absorption rate can be remarkably reduced, but the moisture permeation resistance may increase.

However, in the first embodiment, a second adhesive made of a urea resin-based adhesive, which is inexpensive and has low water resistance, is used as an adhesive together with the first adhesive for molding the medium density fiberboard constituting the field board 21. I am using it. Since the second adhesive has lower water resistance than the first adhesive, medium density fibers having a low water absorption rate (15% or less) can be used in combination with the first adhesive having high water resistance. The board can be formed without increasing the moisture permeation resistance. That is, by adjusting the blending ratio of the first adhesive and the second adhesive, the field board 21 having a water absorption rate of 15% or less and a moisture permeation resistance of less than 2.5 m ² · h · mm Hg / g. Can be configured. In the first embodiment, as described above, the weight ratio of the first adhesive made of the urea-melamine cocondensation resin adhesive and the second adhesive made of the urea resin adhesive is second. Adhesive of 1: 2 Adhesive = 2: 8 By using a medium density fiberboard formed by blending and adding as a field board 21, the water absorption rate is 15% or less and the moisture permeation resistance. The field board 21 having a thickness of less than 2.5 m ² · h · mm Hg / g can be formed.

As for the structural plywood A and structural plywood B which has been conventionally used as a sheathing roof board, moisture permeation resistance, as measured in accordance with a cup method prescribed in JIS A1324 ^is a 23m 2 · h · mmHg / g 27m was ² · h · mmHg / g. From this, it can be seen that the moisture permeation resistance of the field plate 21 of the first embodiment is remarkably low as compared with the conventional field plate, that is, the moisture permeation performance is remarkably high.

[Moisture permeable waterproof sheet]
The moisture permeable waterproof sheet 22 is configured so that the moisture permeable resistance measured in accordance with the cup method specified in JIS A1324 is 0.65 m ² · s · Pa / μg or less. This moisture permeation resistance complies with the regulations of the moisture permeation waterproof sheet for roofs of JIS A6111. In the first embodiment, the moisture permeable waterproof sheet 22 is made of a resin film provided with a large number of micropores (diameter: about 0.5 μm), and has a moisture permeability resistance of 0.5 m ² · s · Pa / μg or less. It is configured. The moisture permeable waterproof sheet 22 may be any material as long as it conforms to JIS A6111, or may be made of a non-woven fabric. Further, these may be laminated.

<Waterproofness of field board>
As described above, since the water absorption rate of the field board (structural plywood) is high in the conventional roof base material, rainwater that reaches the field board through the nail hole penetrating the waterproof sheet penetrates from the surface of the field board to the inside. It was easy. In addition, with conventional roof base materials, the water blocking property of the nail holes that penetrate the field board is low, and when rainwater reaches the field board, it penetrates into the nail holes of the field board, and rainwater is absorbed inside the field board from the nail holes as well. Was there. That is, in the conventional roof base material, the water permeability of the field board is high, and the field board is liable to decay.

On the other hand, in the roof base material 20 of the first embodiment, since the water absorption rate of the field board 21 is low (15% or less), rainwater that reaches the field board 21 through the nail hole of the nail 5 penetrating the moisture permeable waterproof sheet 22. Is difficult to penetrate from the surface of the field board 21 to the inside. Further, in the roof base material 20 of the first embodiment, since the water blocking property of the nail hole is high, it is difficult for rainwater to leak from the nail hole, and it is difficult for rainwater to enter the nail hole, so that rainwater is hard to enter from the nail hole. It is not absorbed by 21. That is, in the roof base material of the first embodiment, the water permeability of the field board 21 is low, and the field board 21 is unlikely to decay.

In order to demonstrate this point, the following water permeability test was conducted.

(1) Test bodies Two of the following two types of test bodies X were prepared.

I: Medium density fiberboard (thickness 9 mm, density 0.79 g / cm ³ , moisture content 8.9%)
II: Plywood (thickness 9 mm, density 0.42 g / cm ³ , moisture content 10.6%, softwood)
The test piece X of I is configured so that the water absorption rate is 15% or less and the moisture permeation resistance is less than 2.5 m ² · h · mmHg / g, similarly to the medium density fiberboard constituting the field board 21. Has been done.

(2) Test method First, as shown in FIG. 3, a test instrument is assembled. Specifically, a nail 51 (N50, screw nail) is driven into the center of the test body X from above. A nail 51 of N50 is driven into one of the test bodies X of I (referred to as test body X1), and a screw nail is driven into the other (referred to as test body X2). A nail 51 of N50 is driven into one of the test bodies X of II (referred to as test body X3), and a screw nail is driven into the other (referred to as test body X4). For each of the four types of test bodies X1 to X4 formed in this way, a cylinder 52 (inner diameter 34 mm, height 300 mm) made of acrylic resin is placed upright on the upper surface of the test body X so as to cover the nail 51. After filling the gap between the cylinder 52 and the upper surface of the test body X with the coking agent 53, these are placed on a beaker 54 having a diameter larger than that of the cylinder 52.

After assembling the test equipment, water (normal temperature) is gently poured into the cylinder 52. Water is poured to a position of 250 mm (about 227 ml) in height of the cylinder 52. Then, these were allowed to stand for 8 days in an environment of a temperature of 20 ° C. and a relative humidity of 65%, and the remaining amount of water, the appearance state of the test body X, and the leakage of water from the nail hole were regularly confirmed.

(3) Test Results The graph in FIG. 4 shows the results of the water permeability test. The amount of water permeation (ml) shown on the vertical axis of the graph of FIG. 4 is the amount of decrease in water poured into the cylinder 52. Further, the ■ mark indicates the test body X1, the ◆ mark indicates the test body X2, the ● mark indicates the test body X3, and the ▲ mark indicates the water permeation amount of the test body X4.

As can be seen from the graph of FIG. 4, among the four types of test bodies X1 to X4, the water permeation amount of the test body X4 is the largest, and the water in the cylinder 52 is almost exhausted on the third day after the start of the test, and the test can be continued. It became impossible. Next, the amount of water permeated by the test body X3 was large, and on the 4th day after the start of the test, the water in the cylinder 52 almost disappeared, making it impossible to continue the test. From this result, in the test bodies X3 and X4, a large nail hole is formed when the nail 51 is driven, so that water spreads (penetrates) in the fiber direction of the test body X from the nail hole and the nail 51 is pushed. It can be seen that it easily passes through the lower part of the test body X (beaker 54) (the water-stopping property of the nail hole is low).

On the other hand, the test bodies X1 and X2 constituting the field plate 21 of the first embodiment have a significantly smaller water permeation amount than the test bodies X3 and X4 among the four types of test bodies X1 to X4, and from the start of the test. Even after 3 days, almost no water flowed out from the inside of the cylinder 52. In the test bodies X1 and X2, water did not drip from the nail 51 to the beaker 54 even after 8 days from the start of the test. This is because in the test specimens X1 and X2, the nail 51 is driven so as to separate the wood fibers, and the wood fibers coated with the adhesive adhere to the nail 51, so that a gap through which water passes is hardly formed. It is presumed that this is due to this. Further, the test body X1 is formed of an adhesive containing a first adhesive having excellent water resistance (in the first embodiment, a urea-melamine cocondensate resin adhesive), and has a water absorption rate of 15% or less. ing. Therefore, even if a gap is formed around the nail 51 by the nail hole, it is presumed that water does not infiltrate because the wood fiber is coated with the first adhesive having excellent water resistance. As described above, in the test bodies X1 and X2, water does not permeate into the inside from the surface (upper surface) and does not penetrate into the nail hole, and the water permeability is significantly lower than that of the test bodies X3 and X4, that is, It can be seen that the waterproof property is extremely high.

-Effect of Embodiment 1-
According to the first embodiment, the field board 21 is composed of a structural medium density fiberboard having a density of 0.7 or more and less than 0.85. Medium density fiberboard is a wood board formed by heat-pressing wood fibers together with an adhesive to form a board, and since gaps are formed between the wood fibers, it has been conventionally used as a field board. Moisture permeability resistance is lower than that of plywood. Therefore, according to the roof base material 20 provided with the field board 21 that easily allows moisture to permeate, even if the humidity generated indoors in winter reaches the back of the cabin, it can permeate the field board 21 and be discharged to the outside. Therefore, moisture does not accumulate on the back surface of the field board 21. Therefore, it is possible to suppress the occurrence of dew condensation on the back surface of the field board 21 and the decay of the field board 21 without providing a ventilation path.

Further, according to the first embodiment, a medium density fiberboard having a water absorption rate of 15% or less is used as the field board 21. Such a field board 21 is less likely to absorb rainwater adhering to the surface than a conventional field board (water absorption rate of 60% or more) made of structural plywood or the like. Further, according to such a field board 21, even at the place where the nail 5 is driven, the wood fiber coated with the adhesive adheres to the nail 5 driven so as to separate the wood fibers, thereby causing the nail. Moisture such as rainwater does not easily enter the holes. By using a medium density fiberboard with excellent waterproofness that does not easily absorb water not only from the surface but also from the nail holes as the field board 21, even if rainwater reaches the roof base material 20 through the gaps in the roofing material 10, it has been conventionally used. In comparison, rainwater is much less likely to permeate the field board 21, and the decay of the field board 21 can be suppressed. Further, even if rainwater permeates the field board 21, it does not reach the back surface, and rain leakage can be prevented.

That is, in the first embodiment, in the roof base material 20 having the field board 21, a medium density fiberboard having an excellent moisture permeability and waterproof property and a water absorption rate of 15% or less is used as the field board 21 to obtain the field board 21. It can prevent decay.

Further, in the first embodiment, as the adhesive for the medium density fiberboard constituting the field board 21, the first type is composed of at least one of a urea-melamine cocondensation resin adhesive having excellent water resistance, diphenylmethane diisocyanate and a phenol resin. Adhesive is used. In such a medium density fiberboard containing the first adhesive, the wood fibers are coated with the first adhesive, so that it becomes difficult for water to penetrate between the wood fibers and the water absorption rate becomes low. On the other hand, if the medium density fiberboard is formed using only the first adhesive having excellent water resistance as an adhesive, the water absorption rate can be remarkably reduced, but the moisture permeation resistance may increase. Further, since the first adhesive having excellent water resistance as described above is expensive, if only the first adhesive is used as the adhesive, the medium density fiberboard also becomes expensive, and the manufacturing cost of the roof base material 20 is high. Is bulky. Therefore, in the first embodiment, it was decided to use a medium density fiberboard using a second adhesive made of a urea resin-based adhesive, which is inexpensive and has low water resistance, as an adhesive together with the first adhesive. Since the second adhesive is inexpensive and has low water resistance, it is possible to obtain a medium density fiberboard having a water absorption rate of 15% or less at a relatively low cost by using it in combination with the first adhesive, which is expensive and has high water resistance. It can be formed without increasing the moisture permeation resistance. Therefore, by using such a medium density fiberboard as the field board 21, it is possible to easily and relatively inexpensively provide the roof base material 20 having the field board 21 having excellent moisture permeability and waterproofness.

Also used in the first embodiment, the density fiberboard in the moisture permeation resistance is configured to be less than 2.5m ² · h · mmHg / g as the sheathing roof board 21. By using the medium density fiberboard having extremely low moisture permeation resistance and excellent moisture permeability as the field board 21, the effect of suppressing the occurrence of dew condensation on the back surface of the field board 21 and the decay of the field board 21 is further increased. To do.

Further, in the first embodiment, the moisture permeable waterproof sheet 22 is provided on the upper surface of the field board 21. That is, a sheet having further moisture permeability and waterproofness is provided on the upper surface of the field plate 21 having excellent moisture permeability and waterproofness. With such a configuration, the waterproof property of the roof base material 20 is further improved, so that the decay of the field board 21 can be further suppressed.

Further, according to the first embodiment, the roof structure 1 provided with the roofing material 10, the roof base material 20, and the heat insulating material 30 has the above-mentioned roof having a field board 21 having excellent moisture permeability and waterproofness and being resistant to decay. The base material 20 is used. By using such a roof base material 20, even if a ventilation path is not provided between the roof base material 20 and the heat insulating material 30, dew condensation on the back surface of the field plate 21 and decay of the field plate 21 are suppressed. be able to. Therefore, by using the roof base material 20, the roof structure 1 that does not easily decay can be easily constructed without a ventilation path, and can be easily constructed.

<< Other Embodiments >>
In the first embodiment, the roof base material 20 is composed of the field board 21 and the moisture permeable waterproof sheet 22, but the roof base material 20 may not include the moisture permeable waterproof sheet 22. As described above, since the field board 21 has lower water permeability and is excellent in waterproofness as compared with the conventional field board, it suppresses rainwater from penetrating into the field board 21 even if the moisture permeable waterproof sheet 22 is not provided. Therefore, it is possible to suppress the decay of the field board 21.

Further, in the first embodiment, an example in which the roof base material 20 according to the present invention is applied to the roof structure 1 of the roof heat insulating type has been described, but the roof base material 20 is not on the roof side but on the ceiling side. Of course, it is also possible to apply it to the ceiling insulation type roof structure provided with. Even when applied to a ceiling insulation type roof structure, the same effect as that of the first embodiment can be obtained.

The present invention is useful for roof base materials and roof structures including them.

1 Roof structure
10 Roofing material
20 Roof base material
21 Field board
22 Breathable waterproof sheet
30 insulation

Claims (5)

It is a roof base material that has a field board and a roofing material can be attached above.
The field board is a roof base material characterized by being composed of a medium density fiberboard having a density of 0.7 or more and less than 0.85 and a water absorption rate of 15% or less. In claim 1,
The medium density fiberboard contains a first adhesive composed of at least one of a urea-melamine cocondensate resin adhesive, diphenylmethane diisocyanate and a phenol resin, and a second adhesive composed of a urea resin adhesive. A roof base material that is characterized by being resin. In claim 2,
The medium density fiberboard is a roof base material characterized in that the moisture permeation resistance is less than 2.5 m ² · h · mmHg / g. In any one of claims 1 to 3,
A roof base material characterized by being provided with a moisture-permeable waterproof sheet provided on the upper surface of the above-mentioned field board. A roof structure of a building including a roofing material, a roofing material to which the roofing material is attached upward, and a heat insulating material provided below the roofing material.
The roof structure of a building, wherein the roof base material is the roof base material according to any one of claims 1 to 4.

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