JP7479036B1 - Exterior wall base material and exterior wall structure - Google Patents

Abstract

[Problem] To provide an exterior wall structure that can be easily constructed with a good finish. [Solution] An exterior wall base material 10 used for the exterior wall W1 of a building comprises a rectangular plate-shaped substrate 11 that serves as a load-bearing surface material, and a moisture-permeable waterproof sheet 12 that covers the entire one side of the substrate 11. The moisture-permeable waterproof sheet 12 has a sheet body 13 and an adhesive layer 14 that bonds the sheet body 13 and the substrate 11, and is configured so that the moisture permeability resistance is 0.19 m2·s·Pa/μg or less. [Selected Figure] Figure 3

Description

The present invention relates to exterior wall base materials and exterior wall structures.

Conventionally, there has been known an exterior wall structure using a ventilation construction method that forms an air passage in the exterior wall of a building such as a house, and discharges moisture that is generated indoors and penetrates the wall to the outside, thereby suppressing the occurrence of condensation inside the wall and improving the efficiency of indoor air conditioning (see, for example, Patent Document 1 below).

The exterior wall structure described in Patent Document 1 is constructed by applying a moisture-permeable load-bearing surface material, a moisture-permeable waterproof sheet, furring strips, and exterior material, in that order, to the exterior side of the structural material. In the exterior wall structure, multiple furring strips are provided parallel to each other at intervals between the moisture-permeable waterproof sheet and the exterior material, forming multiple air passages.

JP 2004-293042 A

However, in the above exterior wall structure, the moisture-permeable waterproof sheet was fixed to the load-bearing surface material with staples or the like at the construction site. Because the moisture-permeable waterproof sheet is thin, soft, and light, it is easily rolled up by the wind and there is a risk of it tearing, making construction difficult. In addition, the moisture-permeable waterproof sheet is prone to wrinkling during construction, and there is a risk that the quality of the finished product will vary depending on the skill of the contractor.

The present invention was made in consideration of these points, and its purpose is to provide an exterior wall structure that can be easily constructed with a good finish.

To achieve the above objective, this invention uses an exterior wall base material in which a moisture-permeable waterproof sheet is pre-attached to one side of the base material that serves as the load-bearing surface material.

Specifically, the first invention is an exterior wall base material used for the exterior walls of a building, comprising a rectangular plate-shaped substrate that serves as a load-bearing surface material, and a moisture-permeable waterproof sheet covering one side of the substrate, the moisture-permeable waterproof sheet having a sheet body and an adhesive layer that bonds the sheet body and the substrate, and is configured so that the moisture permeability resistance value is 0.19 ^m2 ·s·Pa/μg or less.

Here, the moisture permeability resistance of the moisture-permeable waterproof sheet is a value measured in accordance with JIS A6111.

In the first invention, an exterior wall base material is formed by adhering a moisture-permeable waterproof sheet to one side of a rectangular plate-shaped substrate that serves as a load-bearing surface material, such that the moisture permeability resistance value of the entire moisture-permeable waterproof sheet including the adhesive layer is 0.19 ^m2 ·s·Pa/μg or less. By using such an exterior wall base material, a moisture-permeable waterproof sheet that is difficult to apply can be easily applied by simply fixing the exterior wall base material to a structural material that is the framework of a building. In addition, since the exterior wall base material fixes (adheres) the moisture-permeable waterproof sheet to the substrate indoors, such as in a factory, there is little risk of the moisture-permeable waterproof sheet being rolled up or wrinkled during the fixing process, and the finish is uniform. Therefore, according to the first invention, by using the exterior wall base material, an exterior wall structure that can be easily applied with a good finish can be provided.

In addition to the above configuration , the first invention is characterized in that the pressure-sensitive adhesive layer has moisture permeability and covers the entire one side of the sheet body.

In the first invention, the moisture-permeable waterproof sheet is adhered to the entire surface of one side of the substrate by a moisture-permeable adhesive layer that covers the entire surface of one side of the sheet body. By adhering the moisture-permeable waterproof sheet to the entire surface of one side of the substrate in this manner, the moisture-permeable waterproof sheet is less likely to peel off, and the moisture-permeable waterproof sheet does not flap due to wind or the like during construction. Therefore, according to the first invention, construction of the exterior wall structure can be made easier.

The second invention is an exterior wall base material used for the exterior walls of a building, comprising a rectangular plate-shaped substrate which serves as a load-bearing surface material, and a moisture-permeable waterproof sheet which covers the entirety of one side of the substrate, the moisture-permeable waterproof sheet being characterized in having a moisture-permeable sheet body, and a moisture-permeable adhesive layer which is partially or fragmentarily provided on one side of the sheet body and which adheres the sheet body to the substrate.

In the second invention, an exterior wall base material is formed by adhering a moisture-permeable waterproof sheet having a moisture-permeable sheet body and a moisture-permeable adhesive layer to one side of a rectangular plate-shaped substrate that serves as a load-bearing surface material. By using such an exterior wall base material, a moisture-permeable waterproof sheet that is difficult to apply can be easily applied by simply fixing the exterior wall base material to a structural material that is the framework of a building. In addition, since the exterior wall base material fixes (adheres) the moisture-permeable waterproof sheet to the substrate indoors, such as in a factory, there is little risk of the moisture-permeable waterproof sheet being rolled up or wrinkled during the fixing process, and the finish is uniform. Therefore, according to the second invention, by using the exterior wall base material, an exterior wall structure that can be easily applied with a good finish can be provided.

In addition, in the second invention, a moisture-permeable adhesive layer is partially or fragmentarily provided on one side of the sheet body, so that the moisture permeability resistance value of the entire moisture-permeable waterproof sheet can be kept low compared to when the adhesive layer is provided to cover the entire surface of one side of the sheet body.

The third invention is the first invention, characterized in that the substrate is made of a medium density fiberboard containing a water repellent agent so that the contact angle of water with the surface is greater than 90 degrees.

In the conventional method of applying a moisture-permeable waterproof sheet to a load-bearing surface material at a construction site, the load-bearing surface material is attached to the exterior side of the pillar or other structure, and then the moisture-permeable waterproof sheet is generally applied horizontally to encase the exterior wall structure (structure and load-bearing surface material). The sheet is applied starting from the bottom of the exterior wall, and the ends of the moisture-permeable waterproof sheet are attached while shifting upward so that the upper and lower moisture-permeable waterproof sheets overlap partially. The moisture-permeable waterproof sheet is also fixed by driving staples into it using a tacker or the like. In this way, the conventional method of application prevents rainwater from entering through the joints of the load-bearing surface material by completely covering the exterior wall structure with the moisture-permeable waterproof sheet.

In contrast, if an exterior wall base material with a moisture-permeable waterproof sheet already attached to one side of the base material is used, construction of the exterior wall becomes easier, but because the moisture-permeable waterproof sheet cannot cover the joints of the base material (load-bearing surface material), there is a risk of rainwater seeping in through the joints of the exterior wall base material.

Therefore, in the third invention, the base material of the exterior wall base material is made of medium density fiberboard (MDF), which has low water absorption. Medium density fiberboard is a wood board formed by hot pressing wood fibers together with adhesive to form a board, and has a low water absorption rate. Therefore, even if rainwater seeps in through the joints of the exterior wall base material and reaches the base material, the base material will not absorb water and deform (expand in thickness, warp, twist), and mold growth can also be suppressed.

In addition, in the third invention, the medium density fiberboard that constitutes the base material of the exterior wall base material is configured to contain a water repellent agent so that the contact angle of water with the surface is greater than 90 degrees (has water repellency). Therefore, even if rainwater seeps in through the joints of the exterior wall base material, the rainwater turns into water droplets with a contact angle of greater than 90 degrees on the surface of the base material (including the end grain surface), and the water droplets act as stoppers, making it difficult for the rainwater to seep further into the joints of the exterior wall base material. In other words, according to the third invention, even if rainwater seeps in through the joints of the exterior wall base material, it stops at the surface of the base material, and it is possible to prevent the rainwater from seeping further into the interior.

The fourth invention is an exterior wall structure of a building, characterized in that a plurality of exterior wall base materials according to any one of the first to third inventions are attached to the outdoor side of the building's framework, a plurality of vertically extending furring strips are attached to the outdoor sides of the plurality of exterior wall base materials, and a plurality of exterior materials are attached to the outdoor sides of the plurality of furring strips, and between the plurality of exterior wall base materials and the plurality of exterior materials, between each two adjacent furring strips of the plurality of furring strips, an air passage is formed that extends in the vertical direction and has both ends open to the outdoor space.

In the fourth invention, an exterior wall base material is used in which a moisture-permeable waterproof sheet is bonded to one side of a rectangular plate-shaped substrate that serves as a load-bearing surface material in an exterior wall structure using the ventilation construction method, in which an air passage extending vertically is formed inside, so that the moisture permeability resistance value of the entire moisture-permeable waterproof sheet including the adhesive layer is 0.19 ^m2 ·s·Pa/μg or less. By using such an exterior wall base material, it is possible to install a moisture-permeable waterproof sheet, which is difficult to install, simply by fixing the exterior wall base material to the structural material that is the framework of the building, making it easier to install the exterior wall using the ventilation construction method. In addition, since the exterior wall base material fixes (adheres) the moisture-permeable waterproof sheet to the substrate inside a factory or the like, there is a low risk that the moisture-permeable waterproof sheet will be rolled up or wrinkled during the fixing process, and the finish is uniform. Therefore, by using such an exterior wall base material, it is possible to provide an exterior wall structure using the ventilation construction method that can be easily installed by anyone, regardless of the skill of the installer.

In the fourth invention, the moisture permeable waterproof sheet is attached to one side of the base material, but the moisture permeability resistance is kept low (0.19 ^m2 ·s·Pa/μg or less). Therefore, moisture generated indoors can pass through the exterior wall base material and be guided to the ventilation path, and then discharged to the outdoors together with the air.

The fifth invention is the fourth invention, characterized in that the multiple furring strips are positioned to cover and hide the vertically extending joints of the multiple exterior wall base materials from the outside.

As mentioned above, using an exterior wall base material with a moisture-permeable waterproof sheet already attached to one side of the base material makes it easier to construct the exterior wall, but because the moisture-permeable waterproof sheet cannot cover the joints of the base material (bearing surface material), there is a risk of rainwater seeping in through the joints of the exterior wall base material.

Therefore, in the fifth invention, vertically extending furring strips are provided at the joints between multiple exterior wall base materials that extend in the vertical direction, i.e., at the joints between two horizontally adjacent exterior wall base materials, so that the joints are covered and hidden from the outside by the furring strips. This structure makes it possible to prevent rainwater from entering through the joints in the exterior wall base materials.

The sixth invention is the fifth invention, characterized in that the multiple exterior wall base materials are fixed to multiple pillars that form the framework of the building with multiple nails, and the multiple furring strips are positioned to cover and hide the multiple nails and nail holes for fixing the multiple exterior wall base materials to the multiple pillars from the outside.

However, if the exterior wall base material is fixed to the pillars with nails, nail holes will be created in the exterior wall base material, and there is a risk that rainwater will seep in through the nail holes.

Therefore, in the sixth invention, a vertically extending furring strip is provided in a position that covers, from the exterior side, the nail holes formed by driving the nails into the nails used to fasten the exterior wall base materials to the pillars. This structure makes it possible to prevent rainwater from penetrating into the interior of the exterior wall base material through the nail holes.

The seventh invention is an exterior wall structure of a building, in which a plurality of exterior wall base materials according to any one of the first to third inventions are attached to the exterior side of the building's framework, a plurality of furring strips extending to the left and right are attached to the exterior sides of the plurality of exterior wall base materials, and a plurality of exterior materials are attached to the exterior sides of the plurality of furring strips, and the plurality of furring strips are ventilated furring strips in which a communication passage is formed that connects the spaces above and below each of the furring strips so that an air passage extending in the vertical direction with both ends opening to the outdoor space is formed between the plurality of exterior wall base materials and the plurality of exterior materials.

In the seventh invention, an exterior wall base material is used in which a moisture-permeable waterproof sheet is bonded to one side of a rectangular plate-shaped substrate that serves as a load-bearing surface material in an exterior wall structure using the ventilation construction method, in which an air passage extending vertically is formed inside, so that the moisture permeability resistance value of the entire moisture-permeable waterproof sheet including the adhesive layer is 0.19 ^m2 ·s·Pa/μg or less. By using such an exterior wall base material, it is possible to install a moisture-permeable waterproof sheet, which is difficult to install, simply by fixing the exterior wall base material to the structural material that is the framework of the building, making it easier to install the exterior wall using the ventilation construction method. In addition, since the exterior wall base material fixes (adheres) the moisture-permeable waterproof sheet to the substrate inside a factory or the like, there is a low risk that the moisture-permeable waterproof sheet will be rolled up or wrinkled during the fixing process, and the finish is uniform. Therefore, by using such an exterior wall base material, it is possible to provide an exterior wall structure using the ventilation construction method that can be easily installed with a good finish by anyone, regardless of the skill of the installer.

In the seventh invention, the moisture-permeable waterproof sheet is attached to one side of the substrate, but the moisture permeability resistance is kept low (0.19 ^m2 ·s·Pa/μg or less). Therefore, moisture generated indoors can pass through the exterior wall base material and be guided to the ventilation path, and then discharged to the outdoors together with the air.

As explained above, according to the present invention, the construction of exterior walls can be made easier by using an exterior wall base material in which a moisture-permeable waterproof sheet is already attached to one side of the base material that serves as the load-bearing surface material.

FIG. 1 is a vertical cross-sectional view showing an exterior wall structure of a building according to the first embodiment. FIG. 2 is a partially enlarged view of FIG. FIG. 3 is a cross-sectional view showing the exterior wall structure of a building according to the first embodiment. FIG. 4 is a view of an exterior wall structure during construction as viewed from the outside, showing the state after construction of the exterior wall base material and before construction of the furring strips. FIG. 5 is a view of an exterior wall structure during construction as viewed from the outside, showing the state after construction of the furring strips and before construction of the exterior materials.

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

First Embodiment of the Invention
As shown in Figures 1 to 3, the exterior wall structure 1 is used for an exterior wall W1 constructed on the outdoor side of structural materials 2 (pillars 2a, studs 2b, foundations 2c, girder beams 2d, eaves beams 2e, etc.) that form the framework of a building. An interior wall W2 (interior material 3 and moisture-proof sheet 4) is constructed on the indoor side of the structural materials 2. A heat insulating material 5 made of, for example, rock wool is interposed in the space surrounded by the structural materials 2, i.e., between the exterior wall W1 and the interior wall W2.

As shown in Figures 1 to 3, the exterior wall structure 1 comprises a plurality of exterior wall base materials 10, ..., 10, a plurality of furring strips 20, ..., 20, and a plurality of exterior materials 30, ..., 30. The plurality of exterior wall base materials 10 are provided on the exterior side of the structural material 2, the plurality of furring strips 20, ..., 20 are provided on the exterior side of the exterior wall base materials 10, ..., 10, and the plurality of exterior materials 30, ..., 30 are provided on the exterior side of the plurality of furring strips 20, ..., 20.

<Exterior wall base material>
The exterior wall base material 10 comprises a base material 11 and a moisture-permeable waterproof sheet 12. The base material 11 is composed of a rectangular plate-like member that can serve as a load-bearing surface material with a thickness of 5 to 30 mm. The moisture-permeable waterproof sheet 12 is formed in the same rectangular shape and size (width x length) as the base material 11, and is adhered to one side of the base material 11. For example, in this embodiment 1, the exterior wall base material 10 is formed to a size of 910 mm x 3030 mm.

[Base material]
The substrate 11 may be any plate-shaped member capable of serving as a load-bearing surface material, such as porous materials or fibrous materials, such as Dailite (manufactured by Daiken Kogyo Co., Ltd.), volcanic glass laminated board, gypsum board, calcium silicate board, wood fiberboard, and rock wool fiberboard, but from the viewpoint of discharging indoor moisture to the outside and preventing condensation inside the wall, it is preferable to use a material with low moisture permeability resistance as the substrate 11. In this embodiment 1, a medium density fiberboard (MDF) having a density of 0.79 g/ ^cm3 and a thickness of 9 mm is used as the substrate 11.

The medium-density fiberboard constituting the base material 11 contains an adhesive with excellent water resistance. In this embodiment 1, the base material 11 is made of a medium-density fiberboard containing a urea-melamine co-condensation resin adhesive. Note that the adhesive used for the medium-density fiberboard is not limited to a urea-melamine co-condensation resin adhesive, and may contain diphenylmethane diisocyanate, phenolic resin, etc.

(Water repellency)
The substrate 11 is configured so that the contact angle of water with the surface is greater than 90 degrees. Specifically, in the first embodiment, when forming the medium-density fiberboard that constitutes the substrate 11, paraffin, silicone resin, fluororesin, or the like (water repellent) is added in an amount necessary for the surface of the medium-density fiberboard to be water-repellent (the contact angle of water at any point on the surface is greater than 90 degrees).

From the viewpoint of excellent water repellency, it is preferable that the surface of the substrate 11 is configured so that the contact angle with water is 110 degrees or more, and it is even more preferable that the contact angle with water is 120 degrees or more.

(Water Absorption Rate)
The substrate 11 is configured to have a water absorption rate of 15% or less. Preferably, the substrate 11 is configured to have a water absorption rate of 13.6% or less, and more preferably, the substrate 11 is configured to have a water absorption rate of 13.2% or less.

The water absorption rate is calculated by measuring the weight (m1) of a test piece that has reached a constant weight in an environment of 65±5% relative humidity in accordance with the water absorption thickness expansion rate test specified in JIS A5905, placing the test piece in water at 20±1°C, soaking for 24 hours, removing the test piece, measuring its weight (m2), and calculating the difference in weight of the test piece before and after immersion in water (the difference in weight of the test piece before and after immersion (m2-m1) divided by the weight before immersion m1, multiplying this value by 100).

As described above, in medium-density fiberboard containing an adhesive with excellent water resistance, the wood fibers are coated with the adhesive, which makes it difficult for water to penetrate between the wood fibers, resulting in a low water absorption rate. Therefore, by using an adhesive with excellent water resistance to mold the medium-density fiberboard that constitutes the base material 11 and adjusting the blending ratio, the water absorption rate of the base material 11 can be set to the desired water absorption rate, which in this embodiment is 15% or less (preferably 13.6% or less, more preferably 13.2% or less).

The water absorption thickness expansion test was performed on 12 mm thick structural plywood (cedar) and structural plywood (larch surface, cedar core), which are often used as load-bearing surface materials in addition to medium density fiberboard, and the water absorption rates were calculated to be 82% and 61%. This shows that the water absorption rate of the base material 11 of this embodiment 1 is significantly lower than that of structural plywood.

(Moisture permeability)
The substrate 11 is configured so that the moisture permeation resistance measured in accordance with the cup method defined in JIS A1324 is less than 1.2 ^m2 ·s·Pa/μg. Specifically, in the present embodiment 1, the element size (size, diameter, and length of wood fibers) of the medium density fiberboard constituting the substrate 11 is adjusted so that the moisture permeation resistance of the substrate 11 is less than 1.2 ^m2 ·s·Pa/μg.

As described above, a medium-density fiberboard containing an adhesive with excellent water resistance has a low water absorption rate. However, in the present embodiment 1, by adjusting the element size (size, diameter, and length of wood fibers) of the medium-density fiberboard constituting the base material 11, it is possible to form a base material 11 having a moisture permeability resistance of less than 1.2 ^m2 ·s·Pa/μg even if the water absorption rate is 15% or less.

In addition to medium density fiberboard, the moisture permeability resistances of 12 mm thick structural plywood (cedar) and structural plywood (surface layer larch, core layer cedar), which are often used as load-bearing facing materials, measured in accordance with the cup method specified in JIS A1324, were 11 ^m2 ·s·Pa/μg and 13 ^m2 ·s·Pa/μg. This shows that the moisture permeability resistance of the substrate 11 of this embodiment 1 is significantly lower than that of structural plywood, that is, the moisture permeability performance is significantly higher.

[Breathable waterproof sheet]
2 and 3, the moisture-permeable waterproof sheet 12 has a sheet body 13 and an adhesive layer 14 formed on the lower surface of the sheet body 13. The moisture-permeable waterproof sheet 12 is adhered to one side of the substrate 11 by pressing the adhesive layer 14 against one side of the substrate 11 to exert adhesive force. The moisture-permeable waterproof sheet 12 is configured so that the moisture permeation resistance measured in accordance with JIS A6111 is 0.19 ^m2 ·s·Pa/μg or less.

In this embodiment 1, the sheet body 13 is composed of a moisture-permeable waterproof sheet having a moisture permeability of 0.13 m ² s Pa/μg or less as measured in accordance with JIS A6111. More specifically, in this embodiment 1, the sheet body 13 is composed of a resin film such as polypropylene having a thickness of 0.1 to 0.2 mm and a large number of fine pores (diameter of about 0.5 μm) formed therein, and is configured to have a moisture permeability resistance of 0.13 m ² s Pa/μg or less. The moisture-permeable waterproof sheet used as the sheet body 13 may be any material that complies with JIS A6111, and may be composed of a nonwoven fabric. In addition, these may be laminated.

The adhesive layer 14 is formed by applying or transferring an adhesive to one side of the sheet body 13. The adhesive layer 14 may be formed using any adhesive as long as it has sufficient adhesive strength to bond the sheet body 13 to one side of the substrate 11 and the moisture permeability resistance of the moisture-permeable waterproof sheet 12 is 0.19 ^m2 ·s·Pa/μg or less.

In this embodiment 1, the adhesive layer 14 is configured to have a moisture permeability resistance of 0.06 ^m2 ·s·Pa/μg or less as measured in accordance with JIS A6111 (has moisture permeability), and covers one entire side of the sheet body 13.

More specifically, in the present embodiment 1, the adhesive layer 14 is formed by applying or transferring a solution obtained by adding polypropylene glycol, which is a hydrophilic compound, to 5 to 60% by weight of a (meth)acrylic polymer, and mixing an acrylic adhesive composition adjusted to 100% by weight in total with a solvent and an isocyanate composition of 0.5 to 5.0% by weight as a crosslinking agent to the lower surface of the sheet body 13. Examples of the (meth)acrylic polymer used here include 2-ethylhexyl (meth)acrylate and butyl acrylate. In addition, in the acrylic adhesive composition, polypropylene glycol is added at a ratio of 1 to 20 parts by weight per 100 parts by weight of the (meth)acrylic polymer. If the amount added is less than 1 part by weight, the adhesive layer 14 cannot be given the desired moisture permeability resistance (0.06 m ² s Pa/μg or less), and if the amount added is more than 20 parts by weight, it is difficult to form a normal adhesive layer 14, so the amount added is preferably within the above range.

As described above, in the present embodiment 1, an acrylic pressure-sensitive adhesive composition in which 1 to 20 parts by weight of polypropylene glycol is added to 100 parts by weight of a (meth)acrylic polymer and 0.5 to 5.0% by weight of an isocyanate composition is mixed and applied to form a pressure-sensitive adhesive layer 14 having a moisture permeability resistance of 0.06 ^m2 ·s·Pa/μg or less.

In this embodiment 1, it is preferable to form an adhesive layer 14 having a moisture permeability resistance of 0.03 m ² ·s ·Pa/μg or less by foaming or generating bubbles using a commonly used method.

The adhesive layer 14 preferably has a thickness of 10 μm or more and 150 μm or less, and more preferably has a thickness of 30 μm or more and 90 μm or less. If it is thinner than 10 μm, the adhesive strength is low and the moisture-permeable waterproof sheet 12 may easily peel off, and if it is thicker than 150 μm, it is not preferable because the moisture permeability resistance increases.

As described above, the exterior wall base material 10 is constructed by adhering the moisture-permeable waterproof sheet 12 to one side of the base material 11, which serves as the load-bearing surface material. The exterior wall base material 10 is then attached to the structural material 2 by abutting the non-adhesive side of the moisture-permeable waterproof sheet 12 of the base material 11 against the outer surface of the structural material 2, and driving nails 7 through the exterior wall base material 10 from the outdoor side of the exterior wall base material 10 toward the structural material 2.

<Furring strip>
The furring strips 20 are made of long rectangular timbers. In the present embodiment 1, two types of rectangular timbers having different widths are used as the furring strips 20. The multiple furring strips 20, ..., 20 are arranged on the outdoor side of the exterior wall base material 10 at predetermined lengths (e.g., 455 mm) in the left-right direction so that the length direction is the vertical direction, and are fixed (vertically laid) to the outdoor side of the exterior wall base material 10 with nails, staples, or the like.

The wide furring strips 20a are approximately twice as wide as the narrow furring strips 20b. The wide furring strips 20a are positioned to cover and hide the joints (joints 15a extending in the vertical direction, described below) between adjacent exterior wall base materials 10 from the outside, and the narrow furring strips 20b are positioned between two adjacent wide furring strips 20a (see Figures 4 and 5). As shown in Figure 3, the wide furring strips 20a are positioned corresponding to the pillars 2a, and the narrow furring strips 20b are positioned corresponding to the partition posts 2b.

<Exterior materials>
The exterior material 30 may be any surface material that can be used for the exterior wall W1, but in this embodiment 1, the exterior material 30 is made of siding. Also, in this embodiment 1, the multiple exterior materials 30, ..., 30 are arranged on the outdoor side of the furring strips 20 so that their length direction is horizontal, and they are fixed to the furring strips 20 with nails or the like (layed horizontally).

[Air passage]
A plurality of ventilation passages 40, extending in the vertical direction are defined by a plurality of furring strips 20, between a plurality of exterior wall base materials 10, and a plurality of exterior materials 30,. As shown in Fig. 1, each ventilation passage 40 has an inlet at its lower end and an outlet at its upper end, and outdoor air flows from the inlet to the outlet. Air flowing out from the upper end (outlet) of each ventilation passage 40 flows toward the eaves ventilation opening 8 or the ridge ventilation opening (not shown) and is discharged to the outdoors from the eaves ventilation opening 8 or the ridge ventilation opening.

-Wall construction method-
The exterior wall W1 is constructed as follows.

First, multiple exterior wall base materials 10, ..., 10 are nailed with nails 7 to structural materials 2 (pillars 2a, studs 2b, foundations 2c, girder beams 2d, eaves beams 2e, etc.) that form the framework of the building. The multiple exterior wall base materials 10, ..., 10 are attached to the structural material 2 by abutting the non-adhesive surface of the moisture-permeable waterproof sheet 12 of the substrate 11 against the outer surface of the structural material 2 so that the moisture-permeable waterproof sheet 12 is located on the outdoor side of the substrate 11, and driving nails 7 into the structural material 2 from the outdoor side.

As shown in FIG. 4, each exterior wall base material 10 is attached to the structural material 2 by driving multiple nails 7, ..., 7 into the four perimeters and the center of the width direction (left and right direction). Specifically, the exterior wall base material 10 constituting the exterior wall W1 of the first floor part of the building is attached to the columns 2a, 2a at both ends in the width direction, the center in the width direction is attached to the partition 2b, the lower end is attached to the foundation 2c, and the upper end is attached to the girder 2d. The exterior wall base material 10 constituting the exterior wall W1 of the second floor part of the building is attached to the columns 2a, 2a at both ends in the width direction, the center in the width direction is attached to the partition 2b, the lower end is attached to the girder 2d, and the upper end is attached to the eaves beam 2e. Therefore, on the outdoor side of each column 2a, a joint 15a extending in the vertical direction of the exterior wall base material 10 is formed, and on the outdoor side of the partition 2d, a joint 15b extending in the left and right direction of the exterior wall base material 10 is formed.

Before the exterior wall base material 10 is delivered to the construction site, the moisture-permeable waterproof sheet 12 is fixed (glued) to one side of the base material 11 indoors, such as in a factory. Therefore, by simply attaching the exterior wall base material 10 to the structural material 2, the base material 11, which serves as the load-bearing surface material, and the moisture-permeable waterproof sheet 12 can be installed at the same time. The method of attaching the moisture-permeable waterproof sheet 12 to the base material 11 can be any method that involves a process of applying a certain amount of pressure, such as a laminator, roll press, or plate press, and does not need to be heat-pressure.

Next, multiple furring strips 20, ..., 20 are attached to the outdoor side of the multiple exterior wall base materials 10, ..., 10. As shown in Figure 5, furring strips 20 are placed on the outdoor side of the exterior wall base material 10 at predetermined lengths (e.g., 455 mm) in the left-right direction, and fixed to the outdoor side of the exterior wall base material 10 with nails, staples, etc.

Specifically, the wide furring strips 20a are placed on the exterior side of the exterior wall base material 10 at a position corresponding to the pillars 2a, and are fixed to the exterior wall base material 10 with nails, staples, etc. By placing and fixing the wide furring strips 20a in this manner, the multiple joints 15a, ..., 15a extending in the vertical direction of the multiple exterior wall base materials 10, ..., 10, and the multiple nails 7, ..., 7 and their nail holes for fixing each exterior wall base material 10 to the pillars 2a, 2a can be covered and concealed from the exterior side (see Figures 4 and 5).

On the other hand, the narrow furring strips 20b are placed on the exterior side of the exterior wall base material 10 at positions corresponding to the studs 2b, and are fixed to the exterior wall base material 10 with nails, staples, etc. By positioning and fixing the narrow furring strips 20b in this manner, the multiple nails 7, ..., 7 and their nail holes for fixing each exterior wall base material 10 to the studs 2b can be covered and hidden from the exterior side (see Figures 4 and 5).

After the multiple furring strips 20, ..., 20 are installed, multiple exterior materials 30, ..., 30 are attached to the multiple furring strips 20, ..., 20. Specifically, the exterior materials 30 are placed on the exterior side of the furring strips 20 with their length direction oriented horizontally, and the exterior materials 30 are fixed to the furring strips 20 by driving nails into the furring strips 20 from the exterior side, etc.

In this manner, the exterior wall structure 1 is constructed.

-Characteristics of exterior wall structure-
<Ventilation path characteristics>
As described above, in the exterior wall structure 1 of this embodiment 1, a plurality of air passages 40, ..., 40 extending in the vertical direction are defined between a plurality of exterior wall base materials 10, ..., 10 and a plurality of exterior materials 30, ..., 30 by a plurality of furring strips 20, ..., 20.

In each air passage 40, outdoor air flowing in from the lower end (inlet) flows upward and flows out from the upper end (outlet). The air flowing out from the upper end (outlet) of each air passage 40 flows toward the eaves ventilation opening 8 or the ridge ventilation opening (not shown) and is discharged to the outdoors from the eaves ventilation opening 8 or the ridge ventilation opening. Therefore, even if indoor moisture passes through the interior wall W2 (interior material 3 and moisture-proof sheet 4) and the insulation material 5 and reaches the exterior wall base material 10, it passes through the exterior wall base material 10 to reach the air passage 40 and is discharged to the outdoors from the eaves ventilation opening 8 or the ridge ventilation opening together with the air flowing through the air passage 40. Therefore, condensation is less likely to occur in the exterior wall W1. In addition, even if condensation occurs in the exterior wall W1, the condensed water is evaporated into water vapor by the air flowing through the air passage 40 and is discharged to the outdoors from the eaves ventilation opening 8 or the ridge ventilation opening together with the air. This prevents deterioration of the exterior wall base material 10 due to decay.

<Waterproof>
In the exterior wall structure 1 of this embodiment 1, a medium-density fiberboard having a density of 0.7 or more but less than 0.85 and a water absorption rate of 15% or less is used as the base material 11 serving as the load-bearing face material. By using the base material 11 made of medium-density fiberboard having a low water absorption rate as the load-bearing face material in this manner, the water resistance of the load-bearing face material is increased compared to the case where structural plywood is used as the load-bearing face material.

<Water-repellent nail holes>
In addition, in the exterior wall structure 1 of this embodiment 1, a medium density fiberboard with a relatively high density and few voids is used as the base material 11 that serves as the load-bearing surface material, and thus the nail hole water-stopping ability of the load-bearing surface material is dramatically improved compared to the case where structural plywood is used as the load-bearing surface material. It is considered that the nail hole water-stopping ability of the load-bearing surface material is dramatically improved because the wood fibers coated with a water-resistant adhesive or water repellent agent are in close contact with the nails 7 driven in to install the load-bearing surface material (the exterior wall base material 10 in this embodiment 1).

In addition, in this embodiment 1, one side (the surface facing the outdoors) of the base material 11 is covered with a moisture-permeable waterproof sheet 12 having an adhesive layer 14. By covering one side of the base material 11 with a moisture-permeable waterproof sheet 12 having an adhesive layer 14 in this way, even if a nail 7 is driven in when constructing a load-bearing surface material (exterior wall base material 10 in this embodiment 1), the adhesive of the adhesive layer 14 adheres to the nail 7, and the nail-hole water-stopping ability of the moisture-permeable waterproof sheet 12 is dramatically improved.

As described above, the exterior wall structure 1 of this embodiment 1 uses an exterior wall base material 10 in which a moisture-permeable waterproof sheet 12 having an adhesive layer 14 is attached to one side (the outdoor side) of a base material 11 in advance at a factory or the like. Therefore, compared to conventional exterior wall structures in which a moisture-permeable waterproof sheet without an adhesive layer is stapled to a load-bearing surface material with a tacker or the like, the nail hole water-stopping ability of the load-bearing surface material and the moisture-permeable waterproof sheet is dramatically improved.

In addition, in the exterior wall structure 1 of this embodiment 1, wide furring strips 20a, ..., 20a are provided in positions that cover and conceal from the exterior side the multiple nails 7, ..., 7 and their nail holes for fixing each exterior wall base material 10 to the pillars 2a, 2a, and narrow furring strips 20b, ..., 20b are provided in positions that cover and conceal from the exterior side the multiple nails 7, ..., 7 and their nail holes for fixing each exterior wall base material 10 to the studs 2b. Therefore, rainwater will not seep into the interior of the exterior wall base material 10 at least through the nail holes of the nails 7 that are driven from the exterior side of the exterior wall base material 10 toward the pillars 2a and studs 2b.

<Water-stopping at joints>
In the conventional construction method of applying a moisture-permeable waterproof sheet to a load-bearing surface material at a construction site, after the load-bearing surface material is attached to the exterior side of the structure such as a pillar, the moisture-permeable waterproof sheet is generally laid horizontally to envelop the structure of the exterior wall (structure and load-bearing surface material). The moisture-permeable waterproof sheet is attached starting from the lower part of the exterior wall, and the end of the moisture-permeable waterproof sheet is attached while shifting upward so that the upper and lower moisture-permeable waterproof sheets overlap partially. In addition, the moisture-permeable waterproof sheet is fixed by driving staples into the sheet using a tacker or the like. In this way, the conventional construction method prevents rainwater from entering through the joints of the load-bearing surface material by covering the structure of the exterior wall with the moisture-permeable waterproof sheet without any gaps.

In contrast, in the exterior wall structure 1 of this embodiment 1, as described above, an exterior wall base material 10 is used in which a moisture-permeable waterproof sheet 12 is previously adhered to one side of the base material 11. This makes it easier to construct the exterior wall W1, but since the moisture-permeable waterproof sheet 12 cannot cover the joints of the base material 11 (bearing surface material), there is a risk of rainwater seeping in through the joints 15a, 15b of the exterior wall base material 10.

Therefore, in the exterior wall structure 1 of this embodiment 1, the base material 11 of the exterior wall base material 10 is made of medium density fiberboard (MDF), which has low water absorption. Medium density fiberboard is a wood board formed by hot pressing wood fibers together with adhesive to form a board, and has a low water absorption rate. Therefore, even if rainwater seeps in through the joints 15a, 15b of the exterior wall base material 10 and reaches the base material 11, the base material 11 will not absorb water and deform (expand in thickness, warp, twist) or develop mold.

In addition, in the exterior wall structure 1 of this embodiment 1, the medium density fiberboard constituting the base material 11 of the exterior wall base material 10 is configured to contain a water repellent agent so that the contact angle of water with the surface is greater than 90 degrees (has water repellency). Therefore, even if rainwater penetrates through the joints 15a, 15b of the exterior wall base material 10, the rainwater turns into water droplets with a contact angle of greater than 90 degrees on the surface of the base material 11 (including the end grain surface), and the water droplets act as stoppers, making it difficult for the rainwater to penetrate further into the joints 15a, 15b of the exterior wall base material 10.

As described above, in the exterior wall structure 1 of this embodiment 1, wide furring strips 20a extending in the vertical direction are provided at the joints 15a extending in the vertical direction of multiple exterior wall base materials 10, ..., 10, i.e., the joints 15a between two horizontally adjacent exterior wall base materials 10, 10, so that the wide furring strips 20a cover and hide the joints 15a from the outside. This prevents rainwater from seeping in through the joints 15a of the exterior wall base materials 10.

--Effects of the First Embodiment--
In this embodiment 1, an exterior wall base material 10 is formed by adhering a moisture-permeable waterproof sheet 12 to one side of a rectangular plate-shaped substrate 11 serving as a load-bearing surface material, such that the moisture permeability resistance value of the entire moisture-permeable waterproof sheet 12 including the adhesive layer 14 is 0.19 ^m2 ·s·Pa/μg or less. By using such an exterior wall base material 10, the moisture-permeable waterproof sheet 12, which is difficult to apply, can be easily applied by simply fixing the exterior wall base material 10 to the structural material 2 that is the framework of the building. In addition, since the exterior wall base material 10 fixes (adheres) the moisture-permeable waterproof sheet 12 to the substrate 11 indoors, such as in a factory, there is a low risk that the moisture-permeable waterproof sheet 12 will be rolled up or wrinkled during the fixing process, and the finish is uniform. Therefore, according to this embodiment 1, by using the exterior wall base material 10, an exterior wall structure 1 that can be easily applied with a good finish can be provided.

In addition, in this embodiment 1, the moisture-permeable waterproof sheet 12 is adhered to the entire one side of the base material 11 by a moisture-permeable adhesive layer 14 that covers the entire one side of the sheet body 13. By adhering the moisture-permeable waterproof sheet 12 to the entire one side of the base material 11 in this way, the moisture-permeable waterproof sheet 12 is less likely to peel off, and the moisture-permeable waterproof sheet 12 does not flap due to wind or the like during construction. Therefore, according to this embodiment 1, construction of the exterior wall structure 1 can be made easier.

In the conventional method of applying a moisture-permeable waterproof sheet to a load-bearing surface material at a construction site, the load-bearing surface material is attached to the exterior side of the pillar or other structure, and then the moisture-permeable waterproof sheet is generally applied horizontally to encase the exterior wall structure (structure and load-bearing surface material). The sheet is applied starting from the bottom of the exterior wall, and the ends of the moisture-permeable waterproof sheet are attached while shifting upward so that the upper and lower moisture-permeable waterproof sheets overlap partially. The moisture-permeable waterproof sheet is also fixed by driving staples into it using a tacker or the like. In this way, the conventional method of application prevents rainwater from entering through the joints of the load-bearing surface material by completely covering the exterior wall structure with the moisture-permeable waterproof sheet.

In contrast, if an exterior wall base material 10 with a moisture-permeable waterproof sheet 12 already attached to one side of the base material 11 is used, construction of the exterior wall W1 becomes easier, but because the moisture-permeable waterproof sheet 12 cannot cover the joints of the base material 11 (bearing surface material), there is a risk of rainwater seeping in through the joints 15a, 15b of the exterior wall base material 10.

Therefore, in this embodiment 1, the base material 11 of the exterior wall base material 10 is made of medium density fiberboard (MDF), which has low water absorption. Medium density fiberboard is a wood board formed by hot pressing wood fibers together with adhesive to form a board, and has a low water absorption rate. Therefore, even if rainwater seeps in through the joints 15a, 15b of the exterior wall base material 10 and reaches the base material 11, the base material 11 will not absorb water and deform (expand in thickness, warp, twist), and mold growth can also be suppressed.

In addition, in this embodiment 1, the medium density fiberboard constituting the base material 11 of the exterior wall base material 10 is configured to contain a water repellent agent so that the contact angle of water with the surface is greater than 90 degrees (has water repellency). Therefore, even if rainwater penetrates through the joints 15a and 15b of the exterior wall base material 10, the rainwater becomes water droplets with a contact angle of greater than 90 degrees on the surface (including the end grain surface) of the base material 11, and the water droplets act as stoppers to prevent further penetration of the rainwater into the joints 15a and 15b of the exterior wall base material 10. In other words, according to this embodiment 1, even if rainwater penetrates through the joints 15a and 15b of the exterior wall base material 10, it stops at the surface of the base material 11, and further penetration of the rainwater into the interior can be suppressed.

In the present embodiment 1, an exterior wall base material 10 is used in which a moisture-permeable waterproof sheet 12 is bonded to one side of a rectangular plate-shaped substrate 11 serving as a load-bearing surface material in an exterior wall structure 1 according to the ventilation construction method, in which an air passage 40 extending vertically is formed inside, so that the moisture permeability resistance value of the entire moisture-permeable waterproof sheet 12 including the adhesive layer 14 is 0.19 ^m2 ·s·Pa/μg or less. By using such an exterior wall base material 10, the moisture-permeable waterproof sheet 12, which is difficult to install, can be installed simply by fixing the exterior wall base material 10 to the structural material 2 that is the framework of the building, making it easier to install the exterior wall W1 according to the ventilation construction method. In addition, the exterior wall base material 10 fixes (adheres) the moisture-permeable waterproof sheet 12 to the substrate 11 indoors, such as in a factory, so that there is a low risk that the moisture-permeable waterproof sheet 12 will be rolled up or wrinkled during the fixing process, resulting in a uniform finish. Therefore, by using such an exterior wall base material 10, it is possible to provide an exterior wall structure 1 based on a ventilation construction method that can be easily constructed with a good finish by anyone, regardless of the skill level of the installer.

In the first embodiment, the moisture-permeable waterproof sheet 12 is attached to one side of the base material 11, but is configured to have a low moisture permeability resistance (0.19 ^m2 ·s·Pa/μg or less). Therefore, moisture generated indoors can pass through the exterior wall base material 10 and be guided to the ventilation path 40, and then discharged to the outdoors together with the air.

As described above, using an exterior wall base material 10 with a moisture-permeable waterproof sheet 12 already attached to one side of the base material 11 makes construction of the exterior wall W1 easier. However, because the moisture-permeable waterproof sheet 12 cannot cover the joints of the base material 11 (load-bearing surface material), there is a risk of rainwater seeping in through the joints 15a, 15b of the exterior wall base material 10. Rainwater that adheres to the exterior wall base material 10 flows downward, so there is a higher risk of rainwater seeping in through joint 15a, which flows vertically, than through joint 15b, which extends horizontally.

Therefore, in this embodiment 1, wide furring strips 20a extending in the vertical direction are provided at the joints 15a extending in the vertical direction of multiple exterior wall base materials 10, ..., 10, i.e., the joints 15a between two horizontally adjacent exterior wall base materials 10, 10, so that the wide furring strips 20a cover and hide the joints 15a from the outside. This structure makes it possible to prevent rainwater from entering through the joints 15a of the exterior wall base materials 10.

However, if the exterior wall base material 10 is fixed to the pillars (pillars 2a and studs 2b) with nails 7, nail holes will be created in the exterior wall base material 10, and there is a risk that rainwater will seep in through the nail holes.

Therefore, in this embodiment 1, multiple nails 7, 7 for fixing multiple exterior wall base materials 10, 10 to multiple pillars (pillars 2a, 2a and studs 2b, 2b) and their nail holes are provided in a position that covers them from the outside, along with vertically extending furring strips (wide furring strips 20a, 20a and narrow furring strips 20b, 20b). This structure makes it possible to prevent rainwater from entering the interior of the exterior wall base material 10 through the nail holes.

Other Embodiments
In the above-mentioned first embodiment, the adhesive layer 14 of the moisture-permeable waterproof sheet 12 covers the entire one side of the sheet body 13, but as long as the moisture-permeable waterproof sheet 12 can be attached to the substrate 11 without rolling up or wrinkling, the adhesive layer 14 may be formed partially or fragmentarily on one side of the sheet body 13. For example, a plurality of elongated adhesive layers 14 extending in the vertical direction (the length direction of the sheet body 13) may be formed at regular intervals on one side of the sheet body 13.

In addition, when applying anti-corrosion and anti-termite treatment to the portion of the exterior wall W1 up to 1 m above ground level at the construction site, if necessary, it is possible to prepare an exterior wall base material 10 with only a portion (up to 1 m above ground level) with the base material 11 exposed without adhering the moisture-permeable waterproof sheet 12, and after applying the anti-corrosion and anti-termite treatment, the base material 11 is sufficiently dried, and then the moisture-permeable waterproof sheet 12 is attached to the exposed portion of the base material 11.

In the above embodiment 1, the adhesive layer 14 was formed by adding a crosslinking agent to an acrylic adhesive composition in which polypropylene glycol was added to 5 to 60% by weight of a (meth)acrylic polymer. However, the adhesive layer according to the present invention is not limited to the above. The adhesive forming the adhesive layer may contain a (meth)acrylic polymer containing a (meth)acrylic monomer having hydrophilicity that is commonly used, and may further contain components such as hydrophilic additives and tackifiers that are commonly used in adhesives. In addition, isocyanate resins, epoxy resins, metal chelates, etc. that are commonly used in acrylic adhesives may be used as crosslinking agents, and further, a foaming agent may be added, or mechanical foaming may be performed like an acrylic emulsion, etc., so long as the adhesive layer has the desired moisture permeability resistance, any composition or coating method may be used.

In the exterior wall structure 1 of the above-mentioned embodiment 1, multiple furring strips 20, ..., 20 are attached (vertically laid) to the exterior side of the exterior wall base material 10 so that their length direction is vertical (up-down direction), and multiple exterior materials 30, ..., 30 are attached (horizontally laid) to the exterior side of the furring strips 20 so that their length direction is horizontal (left-right direction). However, the exterior wall structure according to the present invention may be attached (horizontally laid) to the exterior side of the exterior wall base material 10 so that multiple furring strips 20, ..., 20 are attached (horizontally laid) to the exterior side of the exterior wall base material 10 so that their length direction is horizontal (left-right direction), and multiple exterior materials 30, ..., 30 are attached (vertically laid) to the exterior side of the furring strips 20 so that their length direction is vertical (up-down direction).

In addition, when the furring strips 20 are laid horizontally and the exterior materials 30 are laid vertically as described above, multiple communication passages that connect the spaces above and below each furring strip 20 are formed in the multiple furring strips 20, ..., 20 to form a ventilated furring strip. The communication passages can be formed by forming holes or grooves that extend vertically from the upper end to the lower end in each furring strip 20, or by providing short furring strips 20 at intervals rather than arranging them horizontally in succession. By forming multiple communication passages in the multiple furring strips 20, ..., 20 in this way (by forming holes or grooves or leaving intervals) to form ventilated furring strips, multiple ventilation paths 40, ..., 40 extending vertically can be formed between the multiple exterior wall base materials 10, ..., 10 and the multiple exterior materials 30, ..., 30, as in the exterior wall structure 1 of embodiment 1. Therefore, even if the exterior wall structure 1 has furring strips 20 laid horizontally and exterior materials 30 laid vertically, the same effect as in embodiment 1 can be achieved.

The present invention is useful for exterior wall base materials and exterior wall structures.

REFERENCE SIGNS LIST 1 Exterior wall structure 2a Pillar 4 Moisture-proof sheet 7 Nail 10 Exterior wall base material 11 Base material 12 Moisture-permeable waterproof sheet 13 Sheet body 14 Adhesive layer 15a Joint 15b Joint 20 Furring strip 20a Wide furring strip 20b Narrow furring strip 40 Ventilation path W1 Exterior wall

Claims (7)

An exterior wall base material used on the exterior wall of a building,
A rectangular plate-shaped base material that serves as a load-bearing surface material;
A moisture-permeable waterproof sheet covering one entire surface of the base material,
The above moisture permeable waterproof sheet is
A seat body,
a moisture-permeable pressure-sensitive adhesive layer that covers one entire surface of the sheet body and bonds the sheet body and the substrate;
An exterior wall base material characterized in that it is configured so that the moisture permeability resistance value is 0.19 ^m2 ·s·Pa/μg or less. An exterior wall base material that is attached to the exterior side of a building frame to form an exterior wall,
A base material composed of a rectangular plate-shaped member serving as a load-bearing surface material;
A moisture-permeable waterproof sheet covering one entire surface of the base material,
The above moisture permeable waterproof sheet is
A moisture-permeable sheet body;
An exterior wall base material characterized by having a moisture-permeable adhesive layer that is partially or fragmentarily provided on one side of the sheet body and adheres the sheet body to the substrate. The exterior wall base material according to claim 1 or 2,
The exterior wall underlayment material is characterized in that the base material is made of a medium density fiberboard that contains a water repellent agent so that the contact angle of water with the surface is greater than 90 degrees. An exterior wall structure of a building,
A plurality of exterior wall base materials according to claim 1 or 2 are attached to the exterior side of the building frame,
A plurality of vertically extending furring strips are attached to the outdoor side of the plurality of exterior wall base materials,
A plurality of exterior materials are attached to the outdoor sides of the plurality of furring strips,
An exterior wall structure characterized in that an air passage extending in the vertical direction with both ends opening to an outdoor space is formed between the plurality of exterior wall base materials and the plurality of exterior materials, and between each two adjacent furring strips of the plurality of furring strips. The exterior wall structure according to claim 4,
An exterior wall structure characterized in that the multiple furring strips are arranged in positions that cover and hide joints extending in the vertical direction of the multiple exterior wall base materials from the outdoors. The exterior wall structure according to claim 5,
The plurality of exterior wall base materials are fixed to a plurality of columns that are the framework of the building with a plurality of nails,
An exterior wall structure characterized in that the multiple furring strips are arranged in a position that covers and conceals the multiple nails and nail holes for fixing the multiple exterior wall base materials to the multiple pillars from the outside. An exterior wall structure of a building,
A plurality of exterior wall base materials according to claim 1 or 2 are attached to the exterior side of the building frame,
A plurality of furring strips extending to the left and right are attached to the outdoor side of the plurality of exterior wall base materials,
A plurality of exterior materials are attached to the outdoor side of the plurality of furring strips,
An exterior wall structure characterized in that the multiple furring strips are ventilated furring strips in which a communication passage is formed between the multiple exterior wall base materials and the multiple exterior materials to connect the spaces above and below each of the furring strips, so that an air passage extending in the vertical direction with both ends opening to the outdoor space is formed between the multiple exterior wall base materials and the multiple exterior materials.