EP3097241A1

EP3097241A1 - A lightweight and watertight low pitch roof structure

Info

Publication number: EP3097241A1
Application number: EP15706054.2A
Authority: EP
Inventors: Martin Schriever
Original assignee: Monier Roofing GmbH
Current assignee: Monier Roofing GmbH
Priority date: 2014-01-20
Filing date: 2015-01-08
Publication date: 2016-11-30
Anticipated expiration: 2035-01-08
Also published as: ZA201603088B; EP3097241B1; PL3097241T3; CN106164391B; CN106164391A; MY175140A

Abstract

The present invention comprises essentially space-apart U-shaped rafters (10) appropriately attached to a truss framework (14), underlays (20) disposed on top extended sections (12) of the rafters (10), and cross battens (40) extending transversely relative to the rafters (10) and serving the purpose of supporting roof tiles (80). Counter battens (30) are employed to press down the underlays (20) to form valleys (21), each being a stretched rigid surface. The roof structure is adapted to be attached at the eave or the verge with fascia boards (60) or wall abutment (70), so that stray rainwater from heavy storms is prevented to enter the roof structure, thus rendering the roof structure watertight.

Description

A LIGHTWEIGHT AND WATERTIGHT LOW PITCH ROOF STRUCTURE

Technical Field

The present invention relates generally to a roof structure comprising essentially spaced-apart rafters extending from eaves to ridge, underlays lying on the top extended section of the rafters, counter battens covering top extended section of the rafters and cross battens extending transversely relative to the rafters and serving to support roof tiles. It relates specifically to underlays being stretched and pressed down by counter battens, each of an approximately omega-shaped cross-section with two side extending flanges, to form valleys. The stretched underlay provides each valley with a rigid surface. The roof tiles are each provided with rain bars.

Background Art

Traditionally, a roof structure includes a plurality of spaced-apart sloping rafters, an underlay being positioned on top extending section of the rafters, and a plurality of cross battens extending transversely relative to the rafters and serving the purpose of supporting roof tiles. The roof tiles are usually laid in successive rows from eaves to ridge, whereby the lower edges of the roof tiles in one row overlap the upper edges of the roof tiles in the row below. The length of the roof tile overlap depends on the roof's pitch. The risk of a leakage is reduced if the roof pitch is very steep (for an example, more than 45 degrees) because it is difficult for the wind to drive rain droplets against the resistance of the slope into the joint between the overlapping roof tiles. Therefore the length of the overlap can be small. If the roof's pitch is shallow (for an example, less than 15 degrees) the resistance of the slope to penetrating rain droplets declines. In this case the length of the overlap must be increased in order to extend the path the rain droplets would have to travel before they could enter the substructure of the roof.

If the pitch of the roof requires a larger overlap between each row of roof tiles from eaves to ridge, a roofer worker has to lay more roof tiles to cover the roof. This increases material and labour costs. Furthermore each additional row of roof tiles increases the load on the roof substructure. From a commercial and technical point of view, conventional roof tiles are therefore unsuitable for roofs with a pitch of less than 15 degrees (such roofs are called in the following ' low pitch roofs').

For low pitch roofs, roof tiles with rain bars were developed, as described in US 7,947,209 B2 and MY-147108-A.

US 7,947,209 B2 discloses a device and method for production of concrete roof tiles each with a rain bar in a valley. The inventive device comprises a forming part with a recess and a ram. The forming part is disposed above the end of a green body of the roof tile, whereupon all or part of the rear edge of the roof tile is pressed upward by means of the ram in order to form a rain bar. The roof tile with integrally moulded rain bar is subsequently cured.

MY-147108-A discloses a roof tile with at least one rain bar in a valley. The rain bar is a thin plate that is inserted in the green body of a roof tile prior to a curing process.

The use of rain bars makes it possible to reduce the overlap between roof tiles and thus the costs and load on the roof. However, experience has shown that the water-tightness of the roof construction remains a problem, especially in the case of wind-driven rain.

In order to improve water-tightness, Malaysian Patent Application PI2013701435 discloses a low pitch roof system which uses a waterproof corrugated sheeting layer below the layer of roof tiles. If rain water occasionally passes over the rain bars, it can fall from roof tiles on to the surface of the sheeting layer and run in the valleys of the corrugations downwards to the eaves.

This solves the problem of water-tightness. Material and labour costs are increased again because a first batten system is required to support the corrugated sheeting layer and a second batten system has to be installed on top of the sheeting layer to support the roof tiles.

EP 1316654 A1 proposes to use flexible underlays instead of a rigid sheeting layer with corrugations. The underlays are laid similar to roof tiles. A first underlay is rolled out in a first row parallel to the eaves so that it covers rafters and an insulating material which is installed between the rafters and supported by a wooden deck fixed on the bottom side of the rafters. When a second underlay is laid on the first row above, the lower longitudinal edge of the second underlay overlaps the upper longitudinal edge of the first underlay, similar to roof tiles. The joint between the overlapping underlays is usually sealed by adhesive means, which ensures a watertight connection between the underlays.

Sealing the joint is relatively easy if the overlapping underlays are supported extensively by a more or less rigid roof substructure, such as known from EP 1316654 A1. However, in some Asian countries, for an example Malaysia, such solid roof substructures are not used.

Summary of the Invention

The present invention has therefore a prime object to provide a lightweight and watertight low pitch roof structure (less than 15 degree pitch).

Other object of the present invention is to allow easy installation by unskilled roofer workers.

Another object of the present invention is to ensure that it is economically beneficial involving fewer battens and fewer materials used.

Yet, another object of the present invention is that the roof structure is non-combustible, structurally stable and resistant to termite, insects and fire.

These objects are achieved by a low pitch roof structure using counter battens, each with an approximately omega-shaped cross-section with two side extending flanges. When installed, the counter battens cover the top extended section of each rafter over its full length from eaves to ridge and the side extending flanges of adjoining counter battens together form two bending lines at the sides of the rafter. The side extending flanges of two neighbouring rafters face each other and press down overlapping underlays along the two opposing bending lines, whereby the underlays are stretched by the side extending flanges to form a valley between two neighbouring rafters. Due to the stretched underlays, the valley, which extends full length from eaves to ridge, has a rigid surface suitable for sealing the joints between the overlapping edges of the underlays by adhesive means. The sealed underlays form a watertight layer below the roof tiles, which is fixed at the cross-battens and rafters. The roof tiles are provided with rain bars in order to improve the resistance of the roof to wind-driven rain.

The low pitch roof structure is adapted to be fitted at the eaves or the verge with fascia boards or wall abutments so that stray rainwater from heavy storms is prevented from entering the low pitch roof structure, thus rendering the roof structure watertight.

Brief Description of Drawings

In order that the present invention may be more readily understood, the following description is given, by way of example, of two methods of constructing a low pitch roof structure according to the present invention. Reference will be made to the accompanying drawings, in which:

Figure 1 shows a partial cross section of a lightweight and watertight low pitch roof structure according to the present invention.

Figure 2a shows how a first underlay is horizontally laid parallel to the roof eaves in the low pitch roof structure as shown in Figure 1.

Figure 2b shows how a second underlay is horizontally laid overlapping the first underlay in the low pitch roof structure as shown in Figure 1.

Figure 2c shows the two overlapping underlays in Figure 2b being pressed down by counter battens and with a sealed joint.

Figure 3a shows how a lightweight and watertight low pitch roof structure can be adapted to be fitted at the verge with fascia boards.

Figure 3b shows how a lightweight and watertight low pitch roof structure can be adapted to be fitted with a wall abutment.

Figure 4 shows how a plurality of rain bar tiles are laid on cross battens transversely disposed to U-shaped rafters and how a lightweight and watertight low pitch roof structure can be adapted to be fitted at the eaves with fascia boards.

Figure 5a shows how a first piece of underlay is vertically laid in an alternative installation of a low pitch roof structure as shown in Figure 1.

Figure 5b shows how two pieces of the underlays are pressed down by counter battens in an alternative vertical installation of the low pitch roof structure as shown in Figure 1.

Detailed Description of Drawings

As seen in Figure 1, a low pitch roof structure comprises a generally plurality of rafters (10), underlays (20), counter battens (30) and cross battens (40) which support roof tiles (80). Roof tiles (80) according to the invention are provided with rain bars (81) but not shown in Figure 1.

To achieve a lightweight roof structure, the rafters (10) are each of U-shaped cross-section channels and made from metallic material including aluminium or zinc coated steel or Zincalume® coated steel. Each U-shaped rafter (10) has a middle web section (11) that is vertically disposed whereas top extended section (12) and bottom extended section (13) are horizontally disposed. The rafters (10) are each attached by securing means (50) via the middle web section (11) to a truss framework (14). The rafters (10) of a low pitch roof structure extend usually from eaves to ridge.

Metallic profiles have the advantage that the roof structure is non-combustible, structurally stable and resistant to termite, insects and fire. To provide sufficient strength and reduce weight, the metallic profile can be a U-shaped cross-section channel. When the truss framework (14) is installed to the middle web section (11) of the rafter (10), the truss framework (14) could interfere with an underlay (20) underneath and it needs to be angled at the top in such a way as to maintain the static load bearing capacity of the rafter (10). This avoids interference between counter battens (30) and the underlay (20) and prevents any damage from installation and wind movement during the design life of the roof.

Each counter batten (30), made from metallic material, is of an approximately omega-shaped cross-section with two side extending flanges (31). The side extending flanges (31) of the counter battens (30) preferably extend over the full length of the counter batten (30), acting as two bending lines (32) for the underlays (20).

The underlays (20) are rollable, flexible plastic or bituminous foils which are waterproof and may or may not be breathable. As shown in Figure 1, a first underlay (20) is rolled-out over two neighbouring rafters (10) and it lies on the top extended sections (12) of the two rafters (10). The first underlay (20) is fixed to each rafter (10) by a counter batten (30) with the assistance of suitable securing means (50). The securing means (50), for an example screws, penetrates the counter batten (30), the underlay (20) and the top extended section (12) of the rafter (10).

When the counter battens (30) are fixed to the rafters (10), t he side extending flanges (31) form two bending lines (32) which are located at the sides of each rafter (10). Opposing side extending flanges (31) of two neighbouring rafters (10) press down the underlay (20) along the bending lines (32). The underlay (20) is stretched by the side extending flanges (31) and forms a valley (21) between the neighbouring rafters (10). The tension in the underlays (20) provides the valley (21) with a rigid surface suitable for applying adhesive means.

Cross battens (40) for the roof tiles (80) extend transversely across the neighbouring rafters (10) and the counter battens (30). The cross battens (40) are fixed in the same way as the counter battens (30) on the rafters (10). The roof tiles (80) - which are not shown in Figure 1 - are provided with rain bars (81) and hooked onto the cross battens (40).

As shown in Figure 2a, a first underlay (20) is laid close and parallel to the eaves. It extends over two neighbouring rafters (10) and is fixed to each rafter (10) by a counter batten (30). The first underlay (20) is pressed down by the counter battens (30) along the bending lines (32) formed by the side extending flanges (31). The tension in the underlay (20) provides the valley (21) with a rigid surface and the bending lines (32) force the underlay (20) into the shape of a rectangular channel.

The length of the counter battens (30) is usually smaller than the width of the underlay (20). The counter battens (30) are fixed in such a way that their lower edge is flush with the lower longitudinal edge of the first underlay (20) ('lower' means eaves-side). Due to their length, the counter battens (30) do not cover the upper longitudinal edge of the first underlay (20) ('upper' means ridge-side). This uncovered area of the underlay (20) is part of an overlapping zone which extends parallel to the upper longitudinal edge of the first underlay (20).

The underlays (20) of the roof structure can easily be installed by two unskilled roofer workers. The first step is to fix the underlay (20) to a first rafter (10) as explained in Fig. 2a. Once the underlay (20) is fixed by a first counter batten (30) a first roofer worker draws it over the second rafter (10) whereby the underlay (20) is stretched. While the first roofer worker maintains the tension on the underlay (20), a second roofer worker applies a second counter batten (30) on the underlay (20) and on second rafter (10). This process is repeated until the first underlay (20) is fixed to all rafters (10) of the roof structure.

The installation of a second underlay (20) is shown in Figure 2b. A second underlay (20) is rolled out parallel to the first underlay (20) and extends over the neighbouring rafters (10). The two underlays (20) overlap each other in the overlapping zone, whereby the lower longitudinal edge of the second underlay (20) covers the upper longitudinal edge of the first underlay (20). Between the overlapping underlays (20) exists a joint (22) which needs to be sealed against the ingress of moisture.

In Figure 2c, the second underlay (20) is fixed by two further counter battens (30) in the same way as described above. The third and fourth counter battens (30) cover the second underlay (20) and the overlapping zone at the rafters (10). In this way the counter battens (30) press the overlapping underlays (20) down and stretch them. As a consequence, the overlapping longitudinal edges of the underlays (20) lie flat and without any gaps between them.

When all underlays (20) and counter battens (30) have been horizontally laid and fixed, the rafters (10) are covered over their full length from eaves to ridge by counter battens (30). The adjoining counter battens (30) on one rafter (10) with their side extending flanges (31) form bending lines (32) from eaves to ridge. As a result, all overlapping underlays (20) are pressed down and stretched over the full length of each rafter (10). The underlays (20) therefore form valleys (21) between the neighbouring rafters (10). Each valley (21) is shaped and stretched over its full length (eaves to ridge direction) and width (between-rafters direction) in order to provide a rigid surface suitable for application of adhesive means.

A low pitch roof structure according to the present invention therefore has valleys (21) between the rafters (10), the valleys (21) being formed by overlapping underlays (20). As the overlapping underlays (20) are bonded together by adhesive means, the valleys (21) form a watertight channel. If strong winds drive rain over the rain bars (81) of the roof tiles (80), raindrops fall into the valleys (21) and can run off to the eaves. And the adhesive means prevent moisture from penetrating the joint (22) between the underlays (20).

It is important to note that screw holes through the counter battens (30) and the underlays (20) are situated above the valleys (21), which represent a rainwater-carrying level. In order to ensure water-tightness, the valleys (21) are free from any penetrations.

Figure 3a and 3b show how the lightweight and watertight low pitch roof structure according to the present invention can be adapted to be fitted at the eaves or the verge with fascia boards (60) or wall abutments (70). By this adaptation, stray rainwater from heavy storms is prevented from entering the roof structure, thus rendering the roof structure watertight.

As seen in Figure 4, the above low pitch roof structure is next fitted with a plurality of spaced-apart cross battens (40) transversely disposed to the counter battens (30) and the U-shaped rafters (10). The roof tiles (80) are provided with rain bars (81) and they are installed over the cross battens (40). Successive rows of roof tiles (80) from eaves to ridge overlap each other. As disclosed in the Malaysian Patent MY-147108-A, a rain bar (81) serves as a water stop and is disposed between a central brim and at least one lateral cover or water beading of a roof tile (80). A rain bar (81) can be a thin metal plate inserted in the fresh concrete prior to the curing of the roof tile (80). Alternatively the rain bar (81) can be made of concrete and produced separately from roof tile (80). In this case the concrete rain bar (81) can be glued on the surface of the roof tile (80). Where one-piece roof tiles (80) are used, each roof tile (80) and each integral rain bar (81) are formed from the same concrete. The rain bar (81) prevents rainwater from ponding on the roof tile (80) and spilling over the head of the roof tile (80) into the roof structure below. During extreme weather, some rainwater may leak through, but the lightweight and watertight low pitch roof structure according to the present invention allows it to drain off the underlays (20).

An alternative installation method to the above installation method is shown in Figures 5a and 5b. For ease of explanation, only three spaced-apart U-shaped rafters (10) are shown. A first piece of underlay (20), preferably with a width of 120 cm, is spread vertically covering the full lengths of the top extended sections (12) of first and second rafters (10) from roof eaves to ridge. Another piece of underlay (20) is spread vertically covering the full lengths of the top extended sections (12) of second and third rafters (10) from roof eaves to ridge, Counter battens (30) are elongated and are employed to press down the underlay (20) to form valleys, being stretched rigid surfaces as previously described. No sealing is required for this vertical installation method, resulting in reduced material input and lower material cost.

Claims

A roof structure comprising essentially spaced-apart rafters (10) extending from eaves to ridges, underlays (20) lying on top extended section (12) of the rafters (10), counter battens (30) covering top extended section (12) of the rafters (10), and cross battens (40) extending transversely relative to the rafters (10) and serving to support roof tiles (80),

is characterized in that,

each counter batten (30) has an approximately omega-shaped cross-section with two side extending flanges (31);

the counter battens (30) cover the full length of each rafter (10) from eaves to ridge;

each underlay (20) is rollable, flexible and waterproof;

the side extending flanges (31) of counter battens (30) are employed to press down and stretch the underlays (20), and to form valleys (21) between neighbouring rafters (10);

the stretched underlay (20) provide each valley (21) with a rigid surface; and

the roof tiles (80) are each provided with rain bars (81).