JPH10292545A - Roof unit and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the production cost of roof units by permitting the simplification of water flashing for downstream portion of a flat roof. SOLUTION: Roof unit B1 of a flat roof construction comprises a flat roof panel almost square in a plan view constituted with a roof surfacing material on a roof framework, small girder wall panels 2 supporting the flat roof panel 1 at four-side edge portions, a small outdoor gable wall panel 3a, a small indoor gable wall panel 3b, and girder truss beam 4 and the like where the vertical surface type structures stated above are jointed together in an intersecting state. In this case, the flat roof surface R is provided with a predetermined drain slope in an arrow direction D on a straight line diagonally connected between a first corner portion and a second corner portion. Therefore, rain water everywhere on the flat roof surface R is collected to one point at the lowest portion near a corner area and thus only a hole 15 for a downspout is required at the corner thereby omitting an expensive roof gutter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a roof unit having a flat roof structure and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, unit buildings have been widely used as one method of increasing the industrial production rate of buildings. This unit building is a building of a system in which one building is divided into several units in advance for factory production, and these are constructed and assembled at a construction site. Units constituting a unit building include a building unit constituting each room portion such as a living room, a dining room, a bedroom, and a children's room of a building, and a roof unit constituting a roof portion of the building. These units are produced in a factory in advance, transported to a construction site, and constructed and assembled on a previously prepared foundation. First, assembling
This is done by installing the building units on the foundation and interconnecting them, and then installing and interconnecting the roof units on top of each installed building unit. By the way, among such roof units, there is a roof unit having a very small water gradient on the roof surface (see Japanese Patent Publication No. 3-39137). As shown in FIGS. 9 and 10, this roof unit has a rectangular flat roof panel 101 in plan view, a small girder wall panel 201 supporting the flat roof panel 101 at four side edges thereof, and a pair of wives. Small wall panels 301a, 3
01b and a girder truss beam 401.

[0003]

However, in the conventional roof unit described in the above publication, a drainage gradient is provided only on a short side direction indicated by an arrow A in FIG. At the bottom of the flat roof surface, the roof rainwater is shielded by the girder small wall panel 201 so as not to fall directly on the ground, so a box-shaped inner gutter (horizon gutter) extending in the long side direction of the flat roof surface. 501 was indispensable. For this reason, there was a problem that the rain closing around the inner gutter 501 was complicated and the cost was high.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a roof unit having a flat roof structure capable of simplifying rainfall under a roof underwater, and a method of manufacturing the same.

[0005]

According to a first aspect of the present invention, a roof frame is attached to an upper surface of a roof frame, and the upper surface is a flat roof surface. The present invention relates to a roof unit in which a square flat roof panel and a plurality of vertical planar structures supporting the flat roof panel are joined to each other in an intersecting state, and the flat roof surface has first obliquely opposed corners. A predetermined water gradient is provided substantially along a diagonal direction connecting the portion and the second corner portion.

According to a second aspect of the present invention, there is provided the roof unit according to the first aspect, wherein each of the first and second vertical planar structures is arranged such that the flat roof panels are arranged adjacent to each other in an intersecting state. Are joined substantially horizontally in an intersecting state, and are joined in a crossing state at a predetermined gradient to respective inner surfaces of the third and fourth vertical planar structures arranged adjacent to each other in an intersecting state. By doing so, the upper surface of the first corner portion sandwiched between the first and second vertical planar structures is the uppermost portion of the flat roof surface, while the third and fourth vertical planar structures are arranged. The upper surface of the second corner portion sandwiched between the flat roof surfaces is the lowermost portion of the flat roof surface.

According to a third aspect of the present invention, there is provided the roof unit according to the first or second aspect, wherein a downspout for dropping rainwater from the roof into the downspout is provided at a lowermost portion of the flat roof surface. It is characterized by being.

[0008] The invention described in claim 4 is based on claim 1,
2. A method for manufacturing a roof unit having a flat roof structure according to item 2 or 3, wherein a flat roof panel having a substantially flat upper surface and a substantially square shape and a plurality of the vertical planar structures are formed, and then the flat roof panel is formed. The first corner portion upper surface is the uppermost portion of the flat roof surface, and the second corner portion upper surface obliquely opposed to the first corner portion is the lowermost portion of the flat roof surface. The flat roof panel is bent downward by a predetermined amount, and the flat roof panel and the plurality of vertical planar structures are joined together while maintaining the bent state, whereby the first corner portion is formed on the flat roof surface. And a predetermined water gradient substantially along a diagonal direction connecting the second corner and the second corner.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a roof unit according to the fourth aspect, wherein a flat roof panel having a substantially flat upper surface and a substantially rectangular shape is provided, and the first to fourth vertical planar structures are provided. And receiving the flat roof panel in the middle of the third or fourth vertical planar structure and substantially along a predetermined inclined line that is a site to be joined to the flat roof panel. After attaching the receiving member, the flat roof panel and the first and second vertical surfaces are sandwiched by the first and second vertical planar structures such that the upper surface of the first corner portion of the flat roof panel is sandwiched between the first and second vertical planar structures. Bonding with the planar structure,
Next, in the step of joining the third or fourth vertical planar structure to the flat roof panel, the second corner upper surface of the flat roof panel is the lowest portion of the flat roof surface.
The flat roof panel is positioned by pressing from above onto the upper surface of the receiving member attached to the inner surface of the third or fourth vertical planar structure, and in this positioned state,
By fixing a side edge portion of the flat roof panel that bends downward to a middle part of the inner surface of the third or fourth vertical planar structure with a fixing tool, the first corner portion and the first corner portion are fixed to the flat roof surface. The present invention is characterized in that a predetermined water gradient is provided substantially along a diagonal direction connecting the second corner portion.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a roof unit according to the fourth aspect, wherein the flat roof panel has a substantially flat upper surface and a substantially rectangular shape, and the first to fourth vertical planar structures. And holding the flat roof panel halfway along the inner surface of the third or fourth vertical planar structure and substantially along a predetermined inclined line that is a portion to be joined to the flat roof panel. After attaching the holding member, the top surface of the first corner portion of the flat roof panel is sandwiched between the first and second vertical planar structures, and the flat roof panel is connected to the first and second vertical structures. In the step of joining the planar structure and the third or fourth vertical planar structure to the flat roof panel, the second corner upper surface of the flat roof panel includes the flat roof surface. So that it is at the bottom of Is positioned from above by the pressing member attached in the middle of the inner surface of the third or fourth vertical planar structure, and is positioned, and in the positioned state, the land roof panel is bent downward. The side edge is the third
Alternatively, by fixing with a fixing tool halfway the inner surface of the fourth vertical planar structure, a predetermined diagonal direction substantially along the diagonal direction connecting the first corner portion and the second corner portion to the flat roof surface. It is characterized by providing a water gradient.

[0011]

According to the structure of the present invention, since the water gradient is provided in the diagonal direction of the substantially rectangular flat roof surface, rainwater reaching the flat roof surface is finally discharged to the lowermost roof roof surface. Can be gathered at the corners of the location. Therefore, for example, if a downspout is provided at this corner,
The necessity of laying an inner gutter (side gutter) along the long side direction of the flat roof surface is eliminated, and therefore, the rainfall at the bottom of the roof can be simplified.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The description will be specifically made using an embodiment. First Embodiment FIG. 1 is a perspective view schematically showing the appearance of a roof unit (underwater roof unit) having a flat roof structure according to a first embodiment of the present invention, and FIG. 2 shows the configuration of the roof unit. FIG. 3 is an exploded perspective view showing an exploded configuration of the roof unit, and FIG. 4 is an explanatory view showing a manufacturing method of the roof unit in the order of steps. , An elevational view schematically showing a unit building having a flat roof structure using the roof unit below the water, and FIG. 6 is a diagram for explaining the operation of the roof unit. It is a top view which shows the structure of the roof part.

The roof unit B1 of this example constitutes the underwater roof part of the unit building C (FIG. 5) having a flat roof structure, and is referred to as the underwater roof unit B1, and has a rectangular flat roof surface in plan view. R (FIG. 6), and the flat roof surface R is provided with a water gradient (FIGS. 1 and 2) in a diagonal direction D connecting two corners obliquely facing each other. The size of the underwater roof unit B1 is, for example, approximately 2,275 mm in the wife (short side) direction and 2,730 to 5,640 mm in the girder (long side) direction. As shown in FIG. 2 and FIG. 3, the underwater roof unit B1 includes a rectangular roof panel 1 that is rectangular in plan view and
And a vertical planar structure such as a girder small wall panel 2, an outdoor side girder wall panel 3a, an indoor side girder small wall panel 3b, and a girder truss beam 4.

As shown in FIG. 3, the flat roof panel 1 has a pair of girder frames 11a and 11b forming long side edges.
And a pair of wife frames 12a, 12b forming a short side edge
, And a plurality of small beams 13, 13, ... that are bridged between the girder frames at a predetermined distance from each other, to attach a roof surface member 14 such as structural plywood to the upper surface of a roof frame assembly that is assembled in a rectangular shape. At one corner (lowest part of the flat roof surface R), which is configured as a flat roof structure, a gutter drop opening 15 for dropping rainwater from the roof into the downspout is provided as necessary. Have been. In addition, various small wall panels 2,
3a and 3b are an upper frame 21 (31a and 31b) and a lower frame 22.
(32a, 32b) and a plurality of vertical frames 23 (33a, 33).
The wall frame 24 (34a, 34b), such as a hard wood chip cement board or a gypsum board, is attached to the inner and outer surfaces or one surface of the wall frame assembled in a rectangular shape by b) to form a bearing wall. In this example, in the girder small wall panel 1 and the outdoor side small wall panel 3a, the upper frames 21, 31a are fixed by nailing to the upper ends of the vertical frames 23, 33a having the same height. In each, it is arranged horizontally,
In the indoor side wife small wall panel 3b, the upper frame 31b is nailed and fixed to the upper edge of each vertical frame 33b whose height is slightly different from each other so as to correspond to the gradient of the indoor side edge of the flat roof surface R. For this purpose, they are arranged with a predetermined gradient (a height difference between both ends of about 45 mm).

Of these small wall panels 2, 3a, 3b, the girder small wall panel 2 supports the flat roof panel 1 at the outdoor side edge of the pair of long side edges of the flat roof panel 1. At the same time, the uppermost part of the outer girder surface of the unit building C is formed. Of the pair of short side edges of the flat roof panel 1, the outdoor side wife small wall panel 3a supports the flat roof panel 1 at the outdoor side edge and constitutes the top of the outer wall wife surface of the unit building C. I do. In addition, the indoor side wife small wall panel 3 b supports the flat roof panel 1 at the indoor side edge of the pair of short side edges of the flat roof panel 1. The girder truss beam 4
Upper chord material 41, lower chord material 42, and these chord materials 41, 42
And the oblique bundle 44 are joined together in a triangular shape by pin bonding, and of the pair of long side edges of the flat roof panel 1, the flat roof panel 1 is formed at the indoor side edge. To support.

The above-structured flat roof panel 1, girder small wall panel 2, outdoor side small wall panel 3a, indoor side small wall panel 3b
And the girder truss beams 4 are formed independently, and then combined and joined in the direction of the arrow as shown in FIG. 3 to form the underwater roof unit B having a water gradient in the diagonal direction D.
1. As shown in FIG. 4A, such a water gradient is generated when the flat roof panel 1 having substantially the same flat surface as the conventional structure is joined to the vertical planar structures 2, 3a, 3b, 4. As shown in FIG. 2B, one corner (underwater) on a diagonal line D in a direction in which a water gradient is to be provided on the upper surface of the flat roof panel 1 is approximately 45 mm with respect to the other corner.
The flat roof panel 1 is bent downward by human power or the like so as to be in a low position, and in this bent state, the vertical planar structures 2, 3b
It is obtained by nailing to

More specifically, in order to obtain the underwater roof unit B1 having the above-described configuration, the flat roof panel 1 is firstly mounted on the inner side of the outdoor side small wall panel 3a (in this example, as shown in FIG. 3). , Approximately 150 mm below the top surface (FIG. 1)), and the outdoor side frame 12a is leveled and joined in an intersecting state. For joining, a panel fixing jig (not shown) is used so that the panels 1 and 3a are positioned in an intersecting state and the flat roof panel 1 is positioned in a horizontal state. The two panels 1 and 3a are connected to the outdoor side small wall panel 3
a vertical frame 33a and the wife frame 12 on the outdoor side of the flat roof panel 1.
This is carried out by placing a nail between them. Next, the flat roof panel 1 and the girder truss beam 4 are joined. Joining is performed between the upper chord material 41 of the girder truss beam 4 and the girder frame 11a of the flat roof panel 1 when the underwater roof unit B1 is installed and the indoor girder frame 11a of the flat roof panel 1 is horizontal. This is done by driving nails. When the flat roof panel 1 is horizontally joined to the girder small wall panel 2 and the girder truss beam 4 which are arranged adjacent to each other, the flat roof panel 1 and the small girder wall panel 2 are then joined. In the joining, both panels 1 and 2 are crossed, and the girder frame 11b of the flat roof panel 1 is positioned at an intermediate position on the inner surface of the girder small wall panel 2 with a predetermined gradient. Bend the corners downward a predetermined amount,
A panel fixing jig (not shown) that maintains this bent state is used.

The two panels 1 and 2 are joined such that the outside surface of the girder frame 11b on the outdoor side of the flat roof panel 1 has a predetermined gradient (approximately 150 m at the left end in FIG.
m, approximately 195 mm (FIG. 1) at the right end), and while maintaining this contact state, the vertical frame 23 of the small girder wall panel 2
This is performed by driving a nail between the flat roof panel 1 and the girder frame 11b. Note that the flat roof panel 1 has a height difference of approximately 45
Deflection of about mm is sufficiently possible with only human power. Finally, the flat roof panel 1 and the girder truss beam 4 are joined. Joining is performed by nailing between the upper frame 31b having the predetermined inclination and the lower frame panel 12b on the indoor side of the flat roof panel 1 as described above. In addition, the flat roof panel 1 and the indoor side wife small wall panel 3b
First, flat roof panel 1 and girder small wall panel 2
May be performed later.

As described above, in the underwater roof unit B1 of this example, the flat roof panel 1 is joined to the girder small wall panel 2 and the outdoor side small wall panel 3a in an intersecting manner in the middle of the roof, thereby providing the roof. Can be prevented from falling directly to the ground, and on the other hand, are joined adjacently to the girder truss beam 4 and the upper inner surface of the indoor side small wall panel 3b when the unit building C is assembled, so that it is arranged adjacently. The integrated continuity of the flat roof surface R between the roof units B1 and B2 can be secured (FIG. 5).

The underwater roof unit B1 includes a waterside roof unit B2 constituting a waterside roof part of a land roof, an intermediate roof unit B2 constituting an intermediate roof part of a land roof,
After being produced in a factory together with the building unit E and the like, it is transported to a construction site, and as shown in FIG. 5, constructed and assembled on a previously prepared foundation to constitute a unit building. In the unit building C configured as described above, when it rains, a water gradient is provided in the diagonal direction of the rectangular flat roof surface R, and therefore, as shown in FIG. The rainwater is collected at one corner of the underwater roof unit B1, which is the lowest part of the flat roof surface R. The collected rainwater is discharged through a downspout 15 provided at this corner. Therefore, the flat roof surface R
There is no need to lay an inner gutter (horizontal gutter) along the long side direction of the roof, and therefore, it is possible to simplify the rainfall under the roof water. In addition, as shown in FIG. 6, when two underwater roof units B1 and B1 are arranged adjacent to each other, the downspout 15 may be provided in only one of them.

Second Embodiment FIG. 7 is an exploded perspective view showing an exploded configuration of a roof unit (underwater roof unit) having a flat roof structure according to a second embodiment of the present invention. The configuration of the second embodiment is significantly different from that of the first embodiment in that it is located in the middle of the small girder wall panel 2A and along a predetermined inclined line which is a portion to be joined to the flat roof panel 1. The receiving member 5 for receiving the flat roof panel 1 is attached in advance. In the second embodiment, when joining the flat roof unit 1 and the small girder panel 2A, the flat roof panel 1 is pressed from above onto the upper surface of the receiving member 5 attached to the inside of the small girder panel 2A. The girder frame 11b on the outdoor side of the flat roof panel 1 that bends downward in this positioned state.
Is nailed and fixed to the vertical frame 23 halfway on the inner surface of the small girder wall panel 2A.

According to the configuration of the second embodiment, the flat roof panel 1 can be easily and accurately positioned with respect to the small girder wall panel 2A without using a precise panel fixing jig. Water gradients can be obtained relatively easily. The second embodiment has substantially the same configuration as that of the first embodiment except that the receiving member 5 is provided. Therefore, in FIG. 7, the same components as those in FIG. And the description is omitted.

Third Embodiment FIG. 8 is an exploded perspective view showing an exploded configuration of a roof unit (underwater roof unit) having a flat roof structure according to a third embodiment of the present invention. In the above-described second embodiment, the receiving member 5 for receiving the flat roof panel 1 is attached in advance along the inner surface of the small girder wall panel 2B and along a predetermined inclined line that is to be joined to the flat roof panel 1. I tried to put it,
The third embodiment is different from the second embodiment in that the receiving member 5 is abolished and the holding member 6 for holding the flat roof panel 1 is attached in advance along the inclined line.
This is different from the embodiment.

In the third embodiment, when joining the flat roof unit 1 and the small girder panel 2B, the flat roof panel 1 is
Pressing member 6 attached in the middle of girder small wall panel 2B
The girder frame 11b on the outdoor side of the flat roof panel 1 that bends downwards in this positioned state is positioned vertically by pressing down on the inner surface of the girder small wall panel 2B.
And fix it with nails. According to the configuration of the third embodiment, substantially the same effects as in the second embodiment can be obtained.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like that do not depart from the gist of the present invention. Is also included in the present invention. For example, the fixing tool is not limited to a nail, and a screw, a rivet, or a joint plate may be used.

In the above-described embodiment, the flat roof panel is bent, and the bent flat roof panel is joined to the vertical planar structure to provide a water gradient along the diagonal direction. Not limited to this, the flat roof panel may be joined to various vertical planar structures in a state where the flat roof panel is inclined diagonally from the beginning.

[0027]

As described above, according to the configuration of the present invention, since the water gradient is provided in the diagonal direction of the substantially rectangular flat roof surface, rainwater reaching the flat roof surface is finally removed. Can be collected at one corner, which is the lowest part of the flat roof surface. Therefore, for example, if a downspout is provided at this corner, there is no need to install an inner gutter (horizontal gutter) along the long side direction of the flat roof surface. You can simplify the process.

According to the second and third aspects of the present invention, a desired water gradient can be easily obtained without using a precise panel fixing jig.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing an appearance of a roof unit (underwater roof unit) having a land roof structure according to a first embodiment of the present invention.

FIG. 2 is a partially cutaway perspective view showing a configuration of the roof unit, partially cut away.

FIG. 3 is an exploded perspective view showing an exploded configuration of the roof unit.

FIG. 4 is an explanatory view showing a method of manufacturing the roof unit in the order of steps.

FIG. 5 is an elevational view schematically showing a unit building having a flat roof structure configured by using the roof unit below water.

FIG. 6 is a diagram for explaining an operation of the roof unit, and is a plan view showing a configuration of a roof portion of the unit building.

FIG. 7 is an exploded perspective view showing an exploded configuration of a roof unit (underwater roof unit) having a flat roof structure according to a second embodiment of the present invention.

FIG. 8 is an exploded perspective view showing an exploded configuration of a roof unit (underwater roof unit) having a flat roof structure according to a third embodiment of the present invention.

FIG. 9 is a schematic view schematically showing the appearance of a conventional roof unit having a flat roof structure and a drainage state of the flat roof surface.

FIG. 10 is a partially cutaway perspective view showing the structure of the roof unit in a partially cutaway manner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flat roof panel (roof panel) 11b Girder frame (flexible side edge of roof panel) 2 girder small wall panel (vertical planar structure) 3a outdoor side wife small wall panel 3b indoor side wife small wall panel 4 digit truss Beam 15 Downspout 5 Receiving member 6 Holding member B1 Underwater roof unit (roof unit) R Flat roof surface

Claims (6)

[Claims] 1. A roof panel having a substantially rectangular flat roof panel having a flat roof surface on the upper surface of a roof framework and having a flat roof surface, and a plurality of vertical planar structures supporting the flat roof panel. And a roof unit joined in an intersecting state with each other, on the flat roof surface, substantially along a diagonal direction connecting a first corner portion and a second corner portion obliquely opposed to each other, A roof unit, wherein a predetermined water gradient is provided. 2. The flat roof panel is substantially horizontally cross-joined to respective inner surfaces of first and second vertical planar structures arranged adjacent to each other so as to cross each other.
The first and second vertical planar structures are joined to the respective inner surfaces of the third and fourth vertical planar structures arranged adjacent to each other in an intersecting state in a crossed state with a predetermined gradient. The upper surface of the first corner portion sandwiched by the body is the uppermost portion of the flat roof surface, while the upper surface of the second corner portion sandwiched by the third and fourth vertical planar structures is the upper surface of the flat roof surface. The roof unit according to claim 1, wherein the roof unit is configured to be the lowermost part of the roof unit. 3. The roof unit according to claim 1, wherein a downspout for dropping rainwater from the roof into the downspout is provided at a lowermost portion of the flat roof surface. 4. A method for manufacturing a roof unit having a flat roof structure according to claim 1, 2, or 3, wherein a flat roof panel having a substantially flat upper surface and a substantially square shape, and a plurality of the vertical planar structures are provided. After forming the body, the first corner top surface of the flat roof panel is the uppermost portion of the flat roof surface, and the second corner top surface obliquely opposed to the first corner portion is the land roof surface. So that it is at the bottom of the surface,
The flat roof panel is bent downward by a predetermined amount, and the flat roof panel and the plurality of vertical planar structures are joined to each other while maintaining the bent state, whereby the first corner angle is formed on the flat roof surface. A method of manufacturing a roof unit, characterized in that a predetermined water gradient is provided along a diagonal direction connecting a portion and a second corner portion. 5. A flat roof panel having a substantially flat upper surface and a substantially square shape, and the first to fourth vertical planar structures, and an inner surface of the third or fourth vertical planar structure. Attaching a receiving member for receiving the land roof panel halfway and substantially along a predetermined inclined line that is a part to be joined with the land roof panel, the first corner upper surface of the land roof panel is Joining the flat roof panel and the first and second vertical planar structures in a manner sandwiched between the first and second vertical planar structures; and then applying the third or fourth vertical surface In the step of bonding the flat structure to the flat roof panel, the second corner upper surface of the flat roof panel is the lowest portion of the flat roof surface,
The flat roof panel is positioned by pressing from above onto the upper surface of the receiving member attached to the inner surface of the third or fourth vertical planar structure, and in this positioned state,
By fixing a side edge portion of the flat roof panel that bends downward to a middle part of the inner surface of the third or fourth vertical planar structure with a fixture, the first corner portion and the first corner portion are fixed to the flat roof surface. 5. The method of manufacturing a roof unit according to claim 4, wherein a predetermined water gradient is provided substantially along a diagonal direction connecting the second corner portion. 6. A flat roof panel having a substantially flat upper surface and a substantially square shape, and the first to fourth vertical planar structures, and an inner surface of the third or fourth vertical planar structure. On the way, and roughly along a predetermined inclined line that is a site to be joined to the flat roof panel, after attaching a holding member for holding the flat roof panel, the first corner upper surface of the flat roof panel is the Joining the flat roof panel and the first and second vertical planar structures in a manner sandwiched between the first and second vertical planar structures; and then applying the third or fourth vertical surface In the step of bonding the flat structure to the flat roof panel, the second corner upper surface of the flat roof panel is the lowest portion of the flat roof surface,
The land roof panel is pressed and positioned from above by the pressing member attached to the inner surface of the third or fourth vertical planar structure, and the land roof panel flexes downward in the positioned state. By fixing a side edge portion of the panel to a middle part of the inner surface of the third or fourth vertical planar structure with a fixture, the first corner portion and the second corner portion are formed on the flat roof surface. 5. The method of manufacturing a roof unit according to claim 4, wherein a predetermined water gradient is provided substantially along a diagonal direction connecting to the roof unit.