EP0516012B1

EP0516012B1 - pitched roofs assembly

Info

Publication number: EP0516012B1
Application number: EP92108770A
Authority: EP
Inventors: Carlo Vitturi; Flavio Guidetti
Original assignee: Dow Italia SRL
Current assignee: Dow Italia SRL
Priority date: 1991-05-30
Filing date: 1992-05-25
Publication date: 1997-03-19
Anticipated expiration: 2012-05-25
Also published as: IT222441Z2; DE69218291T2; ES2100251T3; DE69218291D1; ITMI910474V0; ITMI910474U1; EP0516012A1

Description

This application relates to a pitched roof assembly comprising a roofing insulation board and roofing tiles where the insulation board is adapted for receiving and anchoring corrugated cement and terracotta roofing tiles.
Many buildings, especially in Southern Europe, with pitched roofs are covered by an insulation board and thereafter roofing tiles. Such roofs generally comprise a cement slab or wooden rafters, to which the insulation board is affixed by some manner. The insulation boards are placed on, and optionally affixed, to such roofs, then roofing tiles are laid on the insulation boards, typically using some means of creating ridges on the roof to hold the roofing tiles in place. The roofing tiles have a standard design which generally comprises a corrugated structure with a lip for attachment to the roof at one end, a downward protrusion located near the far end of such tiles, footing lip, which functions to rest the tile against a tile on the next lower row of tiles. The tiles are laid such that the corrugated portions are aligned from row to row allowing air to flow under the tiles in the direction of the corrugation. Corrugation means that each tile has two raised portions, the raised portions resembling half circles. Roofing tile refers herein to a tile used to cover a roof having the desired shape. Such tiles may be fabricated from any material known for use for such tiles, for instance cement or terracotta.
The common method for attaching such tiles to the roofs involve either placing an additional structure on the roof for holding tiles in place, usually a metal or plastic ridge to which the lips of the tiles row are attached. Another solution is to build up a positive ridge on the insulation boards for attaching the lips of the tiles to the roof. Solutions of the above type are represented in DE-A-1609986 and DE-A-2349710
The tiles have a corrugated structure so as to allow air to flow between the insulation board and the tiles. In certain situations, the channel for air flow is insufficient to allow removal of condensation or hot or cold air. Some known insulation boards use vertical grooves in the insulation boards to aid in the transport of liquids, moisture, and air along the channel created by the tiles.
Examples of boards containing vertical grooves aimed at discharging condensation or rain water are given in both DE-A-1609986 and DE-A-2349710. The above cited prior art does not contain any teaching that the vertical grooves must be placed at such reciprocal distance that causes the grooves to be under the center of the raised corrugated portion of the tiles when the roof insulation board is assembed with the commonly employed corrugated cement or terracotta tiles. Moreover, the dimensions of said grooves are not suited to favor ventilation of moisture and air under the roofing tiles.
The described methods for affixing the tiles generally require additional steps or materials. In those embodiments wherein a structure is attached to the roof or the boards to hold the tiles additional steps and materials are required to perform the attachment. In those embodiments where positive ridges are formed on the board additional insulation material is required. Further such additional material must have sufficient strength to hold the tiles on the roof. A second problem is providing for adequate ventilation of water, moisture, and air between the insulation board and roofing tiles. A further problem associated with building up positive ridges on an insulation board is that this requires significant additional processing steps and special machinery to perform this. Any solution to the problems described must take into account the need to maintain the insulating value of the insulating boards.
What is needed is an insulating board which allows for both ventilation and attachment of cement tiles to pitched roofs. What is further needed is such a means which is cost-efficient and does not sacrifice significant insulation value.
The invention is a pitched roof assembly comprising a roofing insulation board and roofing tiles where the insulation board is adapted for anchoring roofing tiles on the pitched roof and comprises an extruded or expanded alkenyl aromatic polymer or a polyurethane based foam board having a thickness of at least 40 mm and has vertical and horizontal grooves and the roofing tiles comprise a corrugated structure with a lip for attachment to the roof at one end, a footing lip located near the far end of such tiles, which functions to rest the tile against a tile on the next lower row of tiles, the tiles being laid in such a way that the raised corrugated portions are aligned from row to row allowing air to flow under the tiles in the direction of corrugation, said pitched roof assembly being characterized in that: (a) the board has a plurality of parallel anchoring grooves adapted for receiving and anchoring roofing tiles, wherein the grooves have a depth of from 10 to 22 mm and a width of from 30 to 50 mm, wherein the adjacent anchoring grooves have a distance between center points which corresponds to the distance from the outside edge of the lip of the tile to the far edge of the footing lip of the tile; (b) the board has a plurality of parallel ventilation grooves perpendicular to the anchoring grooves having a depth of 10 to 22 mm and a width of from 10 to 30 mm, wherein adjacent ventilation grooves have a distance between center points which corresponds to the distance between the center points of adjacent raised corrugated portion of the roofing tiles; (c) the board optionally has on two adjacent edges a projecting flange, and on the other two edges a flange mount; (d) the board has a width (W) according to formula (I) $W = (X)(M) + F$
and a length (L) according to formula (II) $L = (Y)(N) + Z$
wherein

M is the distance which corresponds to the distance from the edge of the lip of the tile to the far edge of the footing lip of the tile;
N is the distance which corresponds to the distance between the center points of adjacent raised corrugated portion of the roofing tiles;
X is the number of anchoring grooves of the board;
F is the additional width of the board due to the optional projecting flange;
Y is the number of ventilation grooves; and
Z is the additional length of the board due to the optional projecting flange.

The boards of these inventions are made from extruded or expanded alkenyl aromatic polymer or polyurethane based foam. Processes for preparing such foams are well-known in the art. The p alkenyl aromatic based polymers preferably are formed by extrusion and have a machine and a transverse direction. The polyurethane foams are preferably formed by reaction injection molding. In a preferred embodiment the alkenyl aromatic polymer based foam is a foam plastic polymer having a plurality of closed non-interconnecting cells, a minimum cross-sectional dimension of at least 30 mm, and a water vapor permeability not greater than 1.8 perm inches as measured by ASTM Method C355-64 Procedures for Desiccant method, said foam body being without discontinuities and substantial variation in average cell size when cell size is measured by averaging cell diameter across the minimum cross-sectional dimension of the body by ASTM method D2842-69.
The design features of the roofing insulation boards are critical to achieve the desired functions in association with roofing tiles. The board has a plurality of horizontal grooves adapted for seating the lips of the cement tiles into the grooves and for holding the cement tiles in place. The depth and the width of such grooves is critical to its successful function for holding the cement tiles in place. The distance from center point to center point of the grooves is critical. Such distance for the anchoring grooves is based on the distance from the outside edge of the lip of a tile to the far edge of its footing lip adapted for abutting the tile against the next lower tile. Preferably, this distance is from 250 to 350 mm, more preferably from 300 to 330 mm and most preferably approximately 315 mm. Therefore the insulation board has a width which is based on multiples of such distance between center points, such width also accommodates any means used to attach adjacent boards. The anchoring grooves are designed such that when two boards are placed on a roof adjacent to one another, the anchoring grooves on adjacent boards have the same distance from center point to center point, thus facilitating the placement of tiles across the two boards. Plurality with respect to the grooves means herein two or more anchoring grooves. The width of the anchoring grooves should be sufficient to receive the lip of the cement tiles designed for holding the tiles on the roof. In a preferred embodiment this groove is wide enough to allow a construction worker to quickly lay tiles adjacent to one another. If the width is too narrow, the construction worker must take great care to place the lip of the tile in the groove thus slowing down the speed and productivity of such a worker. In one embodiment the lip on the cement tile is about 25 mm, therefore the anchoring groove must be greater than 25 mm. At a width equal to that of the anchoring lip the construction worker can lay the tiles but the worker is required to take extreme care in placing the tiles so as not to damage the boards and to insure the tiles are properly seated. Preferably, the width of the anchoring grooves is 5 mm greater than the lip thickness. Preferably the width is 30 mm or greater. At 30 mm or greater a construction worker can more rapidly place cement tiles on a roof adjacent to one another. It has been discovered that above 35 mm, construction workers are able to work very quickly. Conversely, the width of the groove should be no wider than necessary to perform its function, as the area of the insulation board in the vicinity of the groove is thinner than the other parts of the board, thereby reducing the thermal insulating efficiency of the board. It is highly desirable to minimize the loss of thermal insulation efficiency due to the size or width of the grooves. Preferably the width of the anchoring grooves is less than 50 mm, and more preferably less than 45 mm.
The depth of the anchoring groove is such that it is deep enough to receive the lip of the cement tile, such lip is generally 10 to 15 mm long. Therefore the depth of the anchoring groove is preferably 10 mm, more preferably 15 mm or greater, and even more preferably 17 mm or greater. Due to the fact that the groove in the board reduces thermal efficiency, it is desirable that such groove have no greater depth than necessary to perform the stated function. Preferably, the depth of the anchoring groove is 22 mm or less and more preferably 20 mm or less.
The ventilation grooves are perpendicular to the anchoring grooves and parallel to one another. Plurality of ventilation grooves means that at least two ventilation grooves are present. Because the ventilation grooves are designed to aid in the removal of water and moisture and aid in the flow of air that collects between the insulation boards and the cement tiles, and the cement tiles have a corrugated structure which create a channel in the vertical direction on the roof, the placement of the vertical grooves to lie in the middle of such channels created by cement tiles is critical. The distance between center points of ventilation grooves corresponds to the distance between the center points of such channels, ridges or raised portions. Preferably such distance is 100 to 250 mm, more preferably from 100 to 200 mm and most preferably 150 mm. The width of the vertical grooves should be sufficient to allow air and moisture to flow along the channel in the cement tiles. Conversely, the channels should not be so wide as to significantly adversely affect the insulation value of the insulation board. Further, it should be noted that on a roof that uses more than one board end to end, the grooves on the adjacent board should be such that the end groove of each adjacent board have center points which meet the above described criteria.
Preferably the width of the ventilation groove is greater than 10 mm, more preferably greater than 20 mm. Preferably, the width of the ventilation groove is 30 mm or less and more preferably 25 mm or less. The depth of the ventilation groove should be sufficient to allow for transport of moisture, liquids and air along the channels, but not be so great as to adversely affect the insulation value of the board. Such depth is preferably from 10 mm to 22 mm and more preferably from 15 and 22 mm. In a preferred embodiment, the depth of the ventilation grooves is 1 to 2 mm greater than the depth of the anchoring grooves. This is to facilitate the removal of any moisture or liquid which may collect in the anchoring grooves, by creating a natural flow of such moisture or liquid to the ventilation grooves by their greater depth.
The overall dimension of the insulation board is controlled primarily by its function. With respect to the thickness of such board, the board must have sufficient thickness to create thermal insulating value. Furthermore, the board is preferably no thicker than necessary to create sufficient insulating value. Preferably the board has a thickness at its thickest points (or the portion of the board not grooved) of 40 mm or greater, more preferably the boards have a thickness of from 40 to 200 mm.
In a preferred embodiment, the boards of the invention contain flanges and flange mounts to allow adjacent boards laid on a roof to easily interconnect. In utilization of the boards, a plurality of boards will be laid on a roof, and such interconnecting means is valuable. In a more preferred embodiment a protruding flange is located on two adjacent edges, the two opposite edges contain a flange mount. The shape of the flange and flange mount is not critical provided the boards can be firmly abutted one to another when laid on a roof. The flange may be an overlap flange or a tongue-and-groove flange. Preferably the flange protrudes from the board a distance of from 8 mm to 25 mm, or preferably from 9.5 to 14 mm.
In general, the width of the boards is based on the distance between the anchoring grooves and is a multiple of such distance plus any additional width due to the presence of a protuding flange. Formula (I) represents this concept. A primary factor in choosing the width of the board are the available processing machinery and methods. Thus the preferred width of a board, excluding the width according to the flange, preferably 250 mm or greater, more preferably 500 mm or greater. Preferably the width is 1400 mm or less and even more preferably 700 mm or less. In a most preferred embodiment the width is 630 mm, 945 mm or 1260 mm. In those embodiments where the flange is 14 mm, the width of the board is most preferably 644 mm, 959 mm, or 1274 mm.
The length of the boards of this invention are based on the distance between adjacent raised portions of the roofing tiles due to its function. Such length is further influenced by the presence of an optional flange. The concept is represented by Formula (II) which describes the length of the boards. The length of the boards is further limited by practical considerations. If the boards are too long then they become difficult to handle by the construction worker at the construction site. Therefore the length is preferably less than 3000 mm.
Reference to the figures can help illustrate the invention. Figure 1 is a top view of an insulation board according to the invention. The board (10) shows two horizontal anchoring grooves (11). The board (10) further shows a plurality of ventilation grooves (12). Also shown by perspective is the end protuding flange (13) and the side protuding flange (14). Figure 1 demonstrates that when two or more of the boards of this invention are laid side by side the anchoring grooves on adjacent boards will have the requisite distance from one another. Figure 2 demonstrates a cross-section end-view of the board (10). This shows two anchoring grooves (11) the protruding flange for the side (14) and a side flange mount (15). Figure 3 shows a cross-section side view of the board (10) with a plurality of ventilation grooves (12). Further illustrated is an end protruding flange mount (13) and a flange mount at the opposite end (16). Figure 3 shows the first ventilation groove is actually adjacent to the protruding flange and is created by abutting a second board directly to the first board.
The boards of this invention are utilized as described hereinafter. The boards are placed or affixed to a pitched roof. The construction worker would cut the boards to fit the size of the roof where necessary. Further, in those embodiment where flanges are present on the board, the boards are placed such that the flanges insert into the flange mounts of adjacent boards thereby aiding in holding the boards together. These boards may be affixed via adhesive or mechanical means, or simply placed on the roof. In those embodiments where the boards are simply placed on the roof the roofing tiles have sufficient weight to hold the boards on the roof. Once the boards are placed and optionally affixed on the roof, then beginning at the lowest anchoring groove a construction worker quickly places the lips of the roofing tiles in the anchoring groove adjacent to one another so as to create a corrugated structure. Once the first row is completed the construction worker starts on the second row by placing tiles adjacent to one another in the next lowest anchoring groove. Note that the second protruding lip or foot is set adjacent to the tiles in the next lower row, thus abutting the tiles one against another and allowing for an overlap of the tiles. This is continued until the entire roof is covered and then a structure is placed over the peak of the roof to cover the peak. Such means for building up a roof are well-known to those skilled in the art.
Figure 4 demonstrates a finished roof. Figure 4 is a side view of a built-up roof which shows an insulating board (10) having ventilation grooves (12) and anchoring grooves (11). The Figure further shows a series of cement tiles (17). The anchoring lips of the tiles (18) are seated in the anchoring grooves (11). Note further that the cement tiles (17) have a second protruding lip or foot (19) which is laid adjacent to the next lower cement tile to hold the tile in place. It is the distance from the outer edge of the anchoring lip (18) to the far edge of the second lip or foot (19) which is critical. Figure 5 illustrates a placement of the cement tile into an anchoring groove. In particular, the Figure shows a board (10) with an anchoring groove (11) and the placement of a cement tile (17) onto the board with its lip (18) being placed into the anchoring groove (11).
Figure 6 is another perspective view of the boards (10) with tiles thereon from the end of tiles. This is perspective of looking down from the top of the roof at the first row of tile on the board. In this perspective the board (10) has a series of ventilation grooves (12) and anchored in one of the two anchoring grooves (11) are cement tiles (17). The Figure shows how the cement tiles (17) interconnect to one another and create the corrugated structure and thus the channels (19). This further illustrates how the ventilation grooves run through the center of the channels (19) thus allowing for flow moisture, liquids and air to be enhanced along the channels.
The boards of this invention are made by means well-known in the art. In the preferred embodiment the boards are made by extruding a mixture of an alkenyl aromatic based polymer, blowing agents, stabilizers and the like as described hereinafter, in the molten form through a die under conditions such that the polymer expands to form a foam. The use of extruded foam is preferred for this use as it provides strength, such that a foam with negative grooves can hold the roofing tiles without breaking apart.
The polymers or copolymers derived from polymerizable alkenyl aromatic compounds comprise in chemically combined form, at least 50 percent by weight of at least one alkenyl aromatic compound having the general formula
wherein Ar represents an aromatic hydrocarbon radical or an aromatic halo-hydrocarbon radical of the benzene series, which may be optionally substituted with a lower alkyl or alkenyl moiety, and R is hydrogen or the methyl radical. Examples of such alkenyl aromatic resins are the solid homopolymer of styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ethylstyrene, vinylstyrene, chlorostyrene or bromostyrene, the solid copolymers of two or more of such alkenyl aromatic compounds with minor amounts of other readily polymerizable olefinic compounds such as methylmethacrylate, acrylonitrile, maleic anhydride, citraconic anhydride, itaconic anhydride, acrylic acid, rubber reinforced (either natural or synthetic) styrene polymers etc. Most preferred is polystyrene.
In a preferred embodiment the extruded foam bodies are produced by the following procedure. The polymer, and any conventional additives, are melted, and the melt is mixed with a blowing agent composition to give a homogeneous mixture. Mixing is conventionally carried out at from 180° to 280°C, preferably from 200° to 240°C, under a pressure of from 10 to 250 bar. A continuous embodiment in which the mixing is carried out in a conventional single-screw or twin-screw extruder is preferred. The mixture is then let down to a pressure, which is sufficiently lower than the line pressure wherein the lower pressure allows the blowing agent to evaporate advantageously by extrusion though a die, and the blowing agent evaporates and the polymer expands. The resulting foam has a circular or rectangular cross-section, depending on the shape of the die, and stabilizes on cooling. It is preferable to cool the zone into which the foam body is extruded. This may be achieved by encasing the zone with a water jacket with ambient temperature water flowing through the water jacket.
Generally, the preparation of alkenyl aromatic polymer foams is most conveniently performed in a manner generally as shown and described in US Patent No 2,669,751, wherein the volatile fluid blowing agent is injected into a heat-plastified polymer stream within an extruder. From the extruder the heat-plastified gel is passed into a mixer, the mixer being a rotary mixture wherein a studded rotor is enclosed within a housing which has a studded internal surface which intermeshes with the studs on the rotor. The heat-plastified gel from the extruder is fed into the inlet end of the mixer and discharged from the outlet end, the flow being in a generally axial direction. From the mixer, the gel passes through coolers such as are described in US Patent No. 2,668,751 and from the coolers to a die which extrudes a generally rectangular board. A generally similar extrusion system and a preferred extrusion system is shown in US Patent No 3,966,381.
The blowing agent, i.e. foaming agent, used herein can be any known in the art for blowing agent for thermoplastic foams. See for example US 3,770,666; US 4,311,636; US 4,636,527; US 4,438,224; 3,420,786; 4,421,866; (all incorporated herein by reference.) Examples of such blowing agents include commonly used liquid or gaseous organic compounds which do not dissolve the polymer and which have a boiling point below the softening point of the polymer. A wide variety of volatile fluid blowing agents which are carbon-containing compounds; that is, they have carbon chemically combined in their molecules, can be utilized in the practice of the present invention. They include such materials as the aliphatic or cycloaliphatic hydrocarbons including ethane, ethylene, propane, propylene, butane, butylene, isobutane, pentane, neopentane, isopentane, hexane, heptane cyclohexane and mixtures thereof, as well as chlorinated and fluorinated and halogenated hydrocarbons such as methylene chloride, dichlorodifluoromethane, 1-chloro-1,1-difluorethane, 1,1,1,2 tetrafluoroethane, 2-chloro 1,1,1,2-tetrafluoroethane, pentafluoroethane, 2,1,1,1-dichlorodifluoroethane or 1,2,2-trifluoro-1,1,2-trichloroethane may also be used.
Preferably the blowing agents which may be utilized generally exhibit a boiling point of not be greater than about 95°C at 100 kpA of mercury absolute pressure. Other useful fluid blowing agents are the perchlorofluorocarbons, and tetraalkyl silanes, such as tetramethylsilane, trimethylsiliane, trimethylisopropylsilane and trimethyl n-propylsilane, having a boiling point not higher than 95°C at 100 kpA absolute pressure.
Mixtures of these blowing agents may also be employed. It is advantageous to use 3 to 18 percent by weight of blowing agent based on the polymer, and preferably 5 to 15 percent by weight of the polymer of the blowing agent.
In one preferred embodiment the blowing agent is a mixture comprising, from 0-97 weight percent ethyl chloride and from about 3-100 weight percent of a fluorocarbon member selected from the group consisting of chlorodifluoromethane, 1-chloro-1,1-difluoroethane and mixtures thereof.
In addition conventional assistants, fire retardant agents and compositions, lubricants, and fillers may also be employed.
The boards may be prepared with or without appropriate grooves. Preferably, the boards are prepared without grooves and thereafter the grooves are precision cut into the boards using techniques and equipment well known to those in the art.

Claims

A pitched roof assembly (Fig. 4) comprising a roof insulation board (10) and roofing tiles (17) where the roof insulation board comprises an expanded or extruded alkenyl aromatic based or a polyurethane based polymer foam board having a thickness of at least 40 mm and has vertical and horizontal grooves and the roofing tiles comprise a corrugated structure with a lip for attachment to the roof at one end (18), a footing lip (19) located near the far end of such tiles, which functions to rest the tile against a tile on the next lower row of tiles, the tiles being laid in such a way that the raised corrugated portions are aligned from row to row allowing air to flow under the tiles in the direction of corrugation, characterized in that: (a) the board has a plurality of parallel anchoring grooves (11) adapted for receiving and anchoring the roofing tiles, wherein the grooves have a depth of from 10 to 22 mm and a width of from 30 to 50 mm, wherein the adjacent anchoring grooves have a distance between center points which corresponds to the distance from the outside edge of the lip of the tile to the far edge of the footing lip of the tile; (b) the board has a plurality of parallel ventilation grooves (12) perpendicular to the anchoring grooves such ventilation grooves having a depth of from 10 to 22 mm and a width of from 10 to 30 mm, wherein adjacent ventilation grooves have a distance between center points which corresponds to the distance between the center points of adjacent raised corrugated portions of the roofing tiles; (c) the board optionally has on two adjacent edges a projecting flange (13, 14), and on the other two edges a flange mount (15, 16); (d) the board has a width (W) according to formula (I) $W = (X)(M) + F$
and a length (L) according to formula (II) $L = (Y)(N) + Z$
wherein
M is the distance which corresponds to the distance from the far edge of the lip of the tile to the far end of the footing lip of the tile;

N is the distance which corresponds to the distance between the center points of adjacent raised corrugated portion of the roofing tiles;

X is the number of anchoring grooves of the board;

F is the additional width of the board due to the optional projecting flange;

Y is the number of ventilation grooves; and

Z is the additional length of the board due to the optional projecting flange.
A pitched roof assembly according to Claim 1 wherein the distance between the center points of adjacent anchoring grooves (11) of the board (10) is from 250 to 350 mm; and the distance between the center points of adjacent ventilation grooves (12) of the board is from 100 to 250 mm.
A pitched roof assembly according to Claims 1 or 2 wherein the depth of the ventilation grooves (12) of the board (10) is 1 to 2 mm greater than the depth of the anchoring grooves (11).
A pitched roof assembly according to Claims 2 or 3 wherein the anchoring grooves (11) of the board (10) have a width of 35 to 45 mm; and the ventilation grooves (12) have a width of 20 to 25 mm.
A pitched roof assembly according to any one of Claims 1 to 4 wherein the thickness of the board (10) is from 40 to 200 mm.
A pitched roof assembly according to any one of Claims 1 to 5 wherein two adjacent edges of the board (10) have projecting flanges (13, 14), and the other two edges have flange mounts (15, 16).
A pitched roof assembly according to Claim 6 wherein the width of the board (10) is 259.5 to 1414 mm and the length is 3000 mm or less.
A pitched roof assembly according to any one of Claims 1 to 7 wherein the board is made from extruded alkenyl aromatic based polymer.
A pitched roof assembly according to any one of Claims 1 to 8 wherein the board is made from polystyrene.
A pitched roof assembly according to Claim 6 wherein the distance between the center points of the anchoring grooves (11) of the board (10) is 315 mm, the distance between the center points of the ventilation grooves (12) of the board is 150 mm, the depth of the anchoring grooves of the board is from 15 to 22 mm, and the depth of the ventilation grooves of the board is from 15 to 22 mm.
A pitched roof assembly according to Claim 1 wherein the distance between the center points of the anchoring grooves (11) of the board (10) is 315 mm, the distance between the center points of the ventilation grooves (12) of the board is 150 mm, the width of the anchoring grooves and of the ventilation grooves of the board is 30 to 50 mm and 10 to 30 mm, respectively, the depth of the anchoring grooves and of the ventilation grooves of the board is 15 to 20 mm and 15 to 22 mm, respectively, the width (including the flange) of the board is 644 mm, 959 mm or 1274 mm and the length (including the flange) of the board is less than 3000 mm.
A pitched roof assembly according to any of claims 1 to 11 wherein the tiles are cement or terracotta tiles.
A pitched roof assembly according to claim 12 wherein the tiles are cement tiles.