GB2621607A - Cavity wall drainage duct - Google Patents

Abstract

A cavity wall drainage duct or weep vent for discharging water from within a cavity wall construction comprises a hollow box section body (204, fig 3) having opposite open ends 206, 207 and a sloping internal base channel 212 that slopes down towards the external face of the cavity wall. Preferably the sloping internal case channel has a gradient angle of 2 degrees or between 1.8 degrees and 2.1 degrees. The cavity wall drainage duct may have a plurality of projecting ribs 211, 215 to reduce mortar slumping when the perpendicular joint in which the device is located is filled. Preferably the outlet opening is smaller than the inlet opening 207. The inlet opening may be the same height as a masonry brick.

Description

Cavity wall drainage duct This invention relates to a cavity wall drainage duct for integrating into a perpendicular joint of a masonry external wall within a cavity wall construction.

Introduction and background

Cavity wall constructions typically consist of three main parts: The outer leaf which, is the masonry exterior part of the wall that can be brick, block, or stonework. The cavity, the continuous open-air space. The inner leaf, which is the interior part of the wall. The outer leaf is the weathering face and is typically constructed from porous masonry bonded together with mortar on horizontal bed joints and vertical perpendicular joints. Water can seep through the outer leaf into the cavity. This water entering the cavity will run down the cavity face of the outer leaf and will cause damp patches internally when the cavity is bridged by lintels, stop socks, brick supports, through wall ventilators and roof abutments.

To prevent water from tracking across the cavity and causing damp patches that will lead to structural problems, the Building Regulations and British Standards stipulate the use of damp proof course cavity trays to contain any water entering the cavity and advise drainage weep holes in the outer leaf by leaving regular spaced perpendicular joints open and free from mortar between bricks, blocks, or stone. However, the empty weep hole is unsightly and will allow wind driven rain to enter the cavity. The empty weep hole is prone to be filled and blocked. Additionally, the empty weep hole is a gateway for nest building insects and small mammals that will cause infestation problems and structural damage.

It is known to insert proprietary wall weep hole ducts to plug the empty weep holes and allow water drainage of the cavity tray. Such weep hole ducts are small, concealed outlets to offer low visual impact and reduce infestations. However, such proprietary wall weep hole ducts have flat bases and risk becoming blocked from small granules that settle from the water flow.

Mortar is used to bond the masonry outer leaf during construction where a typical bed joint is 10mm thick between courses. The cavity tray is to be bonded centrally in the joint for structural stability resulting in a 4mm thick mortar bed above and below the cavity tray. The proprietary wall weep duct is embedded into the upper 4mm mortar onto the upper surface of the cavity tray. The mortar can ooze into the weep hole duct inlet restricting water drainage flow. Furthermore, water flow from the cavity is combined with small granules of sand and cement from mortar mix. Such solids and liquids require gradients to flow freely for self-cleansing. Gradients that are too steep, liquid drains too quickly and solids left behind. Gradients that are too shallow, limited solid movement within liquid.

Summary of The Invention

According to the present invention there is provided a cavity wall drainage duct with sloping base for draining both water and granular solid for self-cleansing from a cavity of a cavity wall construction. Comprising a hollow box section in an irregular 'L' profile having a sloping base to increase water flow. Sloping gradient is formed by a plurality of projecting ribs of diminishing height leading from a larger inlet opening towards a smaller lower outlet opening. Free from narrowing or restriction. Open apertures to either end project perpendicular from the base to define both a raised inlet and a lower outlet of different size and height. An irregular shaped upper body lofted between the two openings has a plurality of ribs projecting from the body to reduce mortar slumping when perpendicular joints are filled.

Brief Description of The Drawings

Figure 1. Illustrates a cavity wall construction.

Figure 2. Shows a cross section of a preferred embodiment showing exterior wall of a cavity wall, cavity tray and direction of water drainage flow.

Figure 3. Shows a perspective view of a preferred embodiment of a cavity wall drainage duct.

Figure 4. Shows a cross section of a preferred embodiment, illustrated arrow to show direction and gradient angle of water flow.

Figure 5. Illustrates the inlet of a preferred embodiment positioned between bricks of an external wall of a cavity wall Figure 6. Illustrates granule and liquid flow and self-cleansing theory with generic weep duct angled between 0° to less than 1.4°.

Figure 7. Illustrates granule and liquid flow and self-cleansing theory with generic weep duct angled between 0° to less than 1.4°.

Figure 8. Illustrates granule and liquid flow and self-cleansing theory with generic weep duct angled more than 2.5°.

Figure 9. Illustrates the outlet of a preferred embodiment positioned between two bricks of outer leaf of a cavity wall facing externally.

Figure 10. Illustrates a wall with positioning of a preferred embodiments.

Detailed Description of The Preferred Embodiment

The invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 and 2 show a typical cavity wall construction consisting of three main parts: The outer leaf 202, is the masonry external part of the wall facing externally 230 the wall can be brick, block, or stonework and built up vertically in layers known as coursing. The cavity 203, the continuous open-air space. The inner leaf 201, which is the interior part of the wall facing internally 231. The outer leaf 202 is the weathering face and is typically constructed from porous masonry bonded together with mortar on horizontal bed joints 226 and vertical perpendicular joints 209. Water can seep through the outer leaf 202 into the cavity 203. This water entering the cavity will run down the cavity face of the outer leaf 202 and will cause damp patches internally when the cavity is bridged by lintels, stop socks, brick supports, through wall ventilators and roof abutments. To prevent such water from tracking across the cavity 203 and causing damp patches that will lead to structural problems, the Building Regulations part C and British Standards 1358215 stipulate the use of damp proof course cavity trays 223 to cross the cavity from inner leaf 201 to slope downward to the outer leaf 202 to contain water entering the cavity 203 and to drain in the direction shown by arrow 225 via the cavity wall drainage duct 205.

Furthermore, water flow from the cavity 203 is combined with small granules of sand and cement from mortar mix. Mortar is used to bond the masonry outer leaf 202 during construction where a typical horizontal bed joint 226 is 10mm thick between brick courses. The cavity tray 223 is to be bonded centrally in such horizontal joint 226 for structural stability resulting in a 4mm thick mortar bed above and below the cavity tray 223. The cavity wall drainage duct 205 is embedded into the upper 4mm mortar onto the upper surface of the cavity tray 223. The mortar 224 will naturally ooze into the cavity tray as shown as dark shading by weight of bedding the coursed masonry brick 227. Mortar 224 in the cavity 203 that has oozed into the cavity tray 223 is reduced from entering the cavity wall drainage weep 205 by a raised inlet 206 achieved from ribs 211 projecting from the sloping internal base channel 212. Water will drain from the cavity 203 bridging the mortar 224 that has oozed into the cavity tray 223 and drain to outside 230 via the cavity wall drainage duct 204. Furthermore, water flow from the cavity is combined with small granules of sand and cement from mortar mix. Water and granules require optimum gradient to flow freely for self-cleansing.

Figure 3,4 and 5 show perspective views of a cavity wall drainage duct 205 that is Preferably formed in plastics, such as thermoplastic by injection moulding process or alternatively in non-combustible materials.

The cavity wall drainage duct 205 comprises a hollow box section body 204 with wall section 210 nominally 1.5mm thick in an 'L' profile positioned fitted alongside a brick 227 in the outer leaf 202, having a predominantly flat mounting base ribs 211 sitting on a cavity tray 223 spanning the full width of a brick 227 between inlet 206 and outlet 207, integrating a sloping internal base channel 212 to encourage water flow 225. Open apertures 206,207 to both ends are of different heights and project perpendicular from a sloping internal base channel 212 to form the inlet 206 and outlet 207.

An irregular shaped upper body 213 is configured to form a lofted profile between a small outlet opening 207 to one end, and a larger inlet opening 206 to the opposing end. In a preferred embodiment the sloping internal base channel 212 connecting between openings is a preferred angle between 1.4° to 2.5° for optimum granule 221 and water 222 movement for drainage form the cavity tray 223. Direction of fall indicated by an arrow 232 is from the larger inlet opening 206 to the smaller outlet opening 207. Free from narrowing or restriction to encourage water and granule flow.

The body 205 has a plurality of projecting ribs 215,211. The upper body 213 has projecting ribs 215 to reduce mortar slumping when filling perpendicular joints 209 with mortar. The sloping internal base channel 212 has a plurality of projecting ribs 211 of diminishing height leading from a raised inlet opening 206 towards a lower outlet opening 207 to form the sloping internal base channel 212 to increase water flow drainage. Raised Inlet opening 206 to give an overall height of the preferred embodiment to the cavity side of 65mm to equal the size of a masonry brick 227 with a clear opening 7mm x 59mm.

Figure 6 Illustrates granule 221 and water 222 flow and self-cleansing theory with generic weep duct 218 angled between 0° to less than 1.4°, demonstrates limited movement of granule 221 within water 222 that can result in blockage of weep duct and limited drainage capability.

Figure 7 Illustrates granule 221 and water 222 flow and self-cleansing theory with generic weep duct 219 angled between 1.4° to 2.5°, demonstrates the optimum for both granule 221 and water 222 movement that will maintain drainage flow. A preferred embodiment 204 has a sloping lower body 212 at 2° to encourage water flow. Advantageously, the inclined gradient of the preferred embodiment may be between 1.8° and 2.1°.

Figure 8 Illustrates granule 221 and water 222 flow and self-cleansing theory with generic weep duct 220 angled more than 2.5°, demonstrates the water 222 draining too quickly, granules 221 remain in duct that can result in blockage of weep duct and limited drainage capability.

Figure 9 shows the present invention externally from a front elevation demonstrating a concealed outlet 107 oblong in shape with a clear opening 4mm deep by 7mm wide to meet requirements of British Standard BS5250 for aperture size to minimise entry of large nest building insects and vermin to cavity.

Figure 10 shows a perspective view of a brick masonry outer leaf 202 illustrating two cavity wall drainage duct 205 fitted at 450mm centres, firstly with no mortar filling perpendicular joint 209 and second shown with full mortar joint and small outlet 107.

Claims (10)

1. Claims 1. A cavity wall drainage duct for discharging water from a cavity wall construction, the cavity wall drainage duct comprising: a hollow box section body with opposing open ends and having a sloping internal base channel with fall direction from a cavity facing inlet opening down to an externally facing lower outlet opening to increase water drainage flow from inlet to outlet.
2. 2. A device according to claim 1, wherein the sloping internal base channel has a gradient angle of 2°
3. 3. A device according to claim 1, wherein the sloping internal base channel has an inclined gradient of between 1.8° and 2.1°.
4. 4. A device according to claim 1, wherein the sloping internal base gradient angle is defined by a plurality of projecting ribs of diminishing height.
5. 5. A device according to claim 1, wherein the upper body lofted between the two openings has a plurality of ribs projecting from the body to reduce mortar slumping when perpendicular joints are filled.
6. 6. A device according to claim 1, wherein the open ends of said hollow box section are of different sizes.
7. 7. A device according to claim 1, wherein the outlet opening is smaller than the inlet opening.
8. 8. A device according to any of the above claims, wherein the inlet opening is the same height as a masonry brick.
9. 9. A device according to any of the above claims, wherein the device is manufactured from plastic by injection moulding.
10. 10. A device according to any of the above claims, wherein the device is manufactured from non-combustible materials.