GB2233700A - Damp proof courses - Google Patents

Abstract

Plate elements 13 for use in a method of inserting a damp proof course in an existing wall 10 in which a slot is cut generally horizontally along a mortar course through the wall for a length no greater than a self-supporting length of the wall, whereafter the plate elements 13 are pressed into the slot. Each plate element has a thickness substantially equal to the vertical height of the slot, and is formed from an impervious substantially incompressible material. Each plate element 13 pressed into the slot after the first plate element interengages with the previously-fitted next-adjacent plate element in a moisture-tight manner. These stops are repeated until a continuous slot has been formed along the length of the wall with a continuous plurality of adjacent plate elements 13 located in the slot. <IMAGE>

Description

DAMP PROOF COURSES This invention relates to a damp proof plate element suitable for use in performing a method of providing a damp proof course in an existing wall.

Rising damp is a common problem in many older dwellings and occurs either because the building was constructed without a satisfactory damp proof course being incorporated in the walls, or because such damp proof course as was provided has failed and so allows moisture to pass thereacross. Rising damp causes damage to the plaster coat on the wall, to the interior decorations, allows mould to grow and generally gives rise to an unhealthy living environment. As a consequence, it is the practice to attempt to cure rising damp whenever an older property is being renovated; and there have been many proposals for various systems for doing this.

One of the most commonly practised methods for the cure of rising damp is the injection into the wall of a treatment liquid which renders the bricks and mortar from which the wall is constructed impervious to moisture. This is done by drilling into the bricks or the mortar and then injecting under a high pressure a suitable liquid into the drilled holes, such that the liquid is forced to permeate across the whole wall, in the region of the drilled holes. Liquids used for this process include various silicone compounds, latex solutions and aluminium sterate.

The injection process described above does not always produce a satisfactory result, for a number of reasons. For example, the drilled hole may break into a void or cavity in the wall, so preventing sufficient liquid pressure to be built up to cause the liquid to permeate through the whole width of the wall. A relatively hard region of brickwork or mortar may prevent the liquid sufficiently flooding the wall, again leading to inadequate treatment of the brickwork or mortar. For these and other well known reasons, it is found that an injection treatment is not always wholly satisfactory, in producing an adequate barrier to rising damp.

The preferred treatment method for curing rising damp is to insert into a wall a physical (rather than chemical) barrier to the damp. Conventionally, this is done by removing one or more usually two courses of bricks from the wall at the height where the damp proof course is to be installed, placing on the exposed upper surface of the remaining course of bricks a conventional damp proof course material, and then replacing the bricks so as to integrate the damp proof course material into the wall. It is however very difficult satisfactorily to replace the bricks, with a full mortar layer both above and below the replaced bricks; the action of sliding a brick back into place in the wall inevitably forces out the mortar above and below that brick.Moreover, the process is very slow and tedious to perform: only a relatively short length of brickwork may be removed from the wall at any one time to ensure the brickwork above the removed courses is self-supporting, and following the replacement of the bricks, sufficient time must be allowed for the mortar to set before the next adjacent section of brickwork may be removed. It is also known to cut a narrow slot through the wall, using a suitable mechanical device such as a saw, and then to place in that slot the conventional damp proof course material, whereafter mortar has to be injected between that material and the brickwork above the material. This method thus also suffers from much the same disadvantages.

It is a principal aim of the present invention to provide a plate element suitable for use in a method of inserting a damp proof course in an existing wall, the use of which plate element which at least reduces the disadvantage of the use of a conventional damp proof material as described just above.

Accordingly, the invention provides a plate element for use in a method of inserting a damp proof course in a wall, in which method a slot is cut generally horizontally through the wall and a plurality of the plate elements are pressed into that slot, which said plate element comprises a piece of generally rectangular, substantially incompressible waterimpermeable material, the plate element having along one edge a re-entrant groove and along the opposed edge a complimentarily formed projection whereby one plate element being fitted into a slot in a wall may be mechanically interlocked with the next adjacent plate in the slot so as thereby to provide a continuous damp proof course.

In performing a damp proofing method using plate elements of the present invention, it will be appreciated that a mechanical damp proof course is provided, this giving a reliable moisture break and so positively curing rising damp. Appropriate selection of the plate material will moreover ensure the course has an adequate life expectancy. However, the method is relatively fast and easy to perform as compared to the conventional method of inserting a physical damp proof course, where brickwork has to be removed and then replaced, or mortar has to be injected or otherwise forced into a mechanically cut slot.Instead, using plates of this invention, a relatively wide (about 10 mm high) slot is cut with a suitable tool through the wall, the length of the slot being such that no collapsing of the brickwork above the slot takes place, and then the water impermeable plate elements are press-fitted into the slot so as substantially wholly to fill the vertical extent of that slot. Since no mortar is employed, immediately after plate elements have been pressed into the slot, a further length of slot may be cut and the process continued, until the entire length of the wall to be treated has had the damp proof plate elements inserted thereinto.

The slot should be cut so as to have a substantially constant, known vertical extent, in order that the plate elements may be a close fit in that slot. In this way, settlement of the wall as the damp proofing process continues may be maintained at a minimum. The slot itself may be cut through the wall at any suitable height, though it is preferred to cut along the length of a mortar course, rather than through the brickwork itself. For actually cutting the slot, various tools could be used such as hand saws, rotary cutting wheels or saws, or a kind of chainsaw, specifically adapted for use in cutting masonry. The chain of such a chainsaw may have hard, abrasionresistant cutting tips and should be driven at a relatively low speed.

Each plate element of this invention should be of a relatively hard and durable material, so as to be able to withstand the load which will be applied thereto by the building wall above the plate elements, when in service, and in order to give the damp proof course a long life expectancy. Each plate element may however be slightly flexible, to assist the alignment and insertion of the plate into the slot. Such plate elements may be manufactured from a suitable grade of a plastics material, but it is most important that the selected plastics material has very high crushresistant properties as well as virtually no flow or creep properties, in order to prevent collapse of the plate elements under the weight of the wall above the inserted course. To this end, if the plate elements are to be made of a plastics material, it may be necessary to incorporate a suitable reinforcing material in each plate element during the moulding thereof.

It is most important that the integrity of the damp proof course is maintained at the junction between adjacent plate elements. This is achieved by means of the mechanical interlock formed on opposed edges of each plate element, which may take the form of a dovetail-shaped groove on one edge and a complimentarily projection on the opposed edge, so that the projection on one plate element may be interlocked with the groove on the next adjacent plate element, as the plate elements are fitted into the slot. Mastic or a suitable water-proofing agent may be used on the inter-fitting projections and grooves, to ensure there is no possibility of capillary action over the mechanical interlocking joint between adjacent plate elements.

By way of illustration only, one specific example of plate elements for use in a method of inserting a damp proof course into a wall, which plate elements are constructed in accordance with the present invention,will now be described in detail, reference being made in the accompanying drawings, in which: Figure 1 is a perspective view of a wall during the treatment thereof by a method using plate elements of this invention; and Figure 2 is a detailed view on part of two interlocking plate elements.

In order to insert a damp proof course in a wall illustrated in Figure 1 and constructed in conventional brickwork, a slot is cut with a suitable tool wholly through the thickness of the wall, in the mortar between two adjacent courses 11 and 12 of the brickwork. The slot should be cut so as to have an essentially uniform vertical extent of about 10 mm, and so will be approximately equal to the height of the mortar course between the two brickwork courses 11 and 12. The length L of slot cut along the wall must be less than that at which there would be a risk of the brickwork above the slot collapsing into that slot.

Typically therefore the length of the slot should be no more than 1 m, for conventional brickwork.

When the slot has been completed, water-impervious plates 13 are press-fitted into the slot, each plate having a vertical extent of substantially 10 mm. Some force may therefore have to be applied to each plate, in order to ensure that it may be pressed fully into the slot.

Each plate should have a width substantially equal to the width of the wall being treated, and consequently typically would have a width of about 230 mm (about 9 ins). Conveniently, each plate has a similar length, so that each plate is essentially of square shape, when considered in plan; three such plates may thus be fitted into the slot the cut length L of which should be about 1 m, as mentioned above.

Each plate 13 has formed along one edge a dovetail-shaped groove 14, and along the opposed edge a complimentarily formed projection 15, engageable in the groove of an adjacent plate. As each plate is fitted into the slot, the projection 15 on one plate should be interengaged with the groove 4 on the other plate so as to ensure the plates are mechanically joined together in the correct disposition. Conveniently, and to assist the proper insertion of the plates as the installation of the damp proof course proceeds, a plate is only partially inserted into the slot before the next plate is engaged therewith, ready for insertion, as illustrated in Figure 1.Thus, the third plate to be inserted in a slotof length L is left projecting out of that slot to some extent at the time the slot is extending by cutting for a further length L, so as to facilitate the interengagement of the next plate within the last-inserted plate.

Each plate may be formed of a reinforced plastics material, by a suitable moulding process. For example, each plate may be made from an epoxy or similar plastics resin, reinforced with glass or carbon fibres.

Whatever material is chosen, it should have high compressive strength, high resistance to attack by water, salts, alkalis and other chemicals, and very low creep or flow properties, bearing in mind the service conditions of a high load to be withstood continuously for many, many years.

In order to ensure the integrity of the damp proof course provided by the method of this invention, a mastic or similar water-proof material may be included in the groove of a plate being pressed into the slot, during the insertion step, so as to form a water-proof bond with the adjacent, previously inserted plate.

An advantage of the described method of providing a damp proof course is that the course is visible when completed, unlike many of the known methods where the existence of a damp proof course cannot easily be established.

Reference is directed to our co-pending Application No. 86 29506 (Serial No. 2,198,469) which is directed to and claims the method described above, using plate elements of this invention.

Claims (11)

1. A plate element for use in a method of inserting a damp proof course in a wall, in which method a slot is cut generally horizontally through the wall and a plurality of the plate elements are pressed into that slot, which said plate element comprises a piece of generally rectangular, substantially incompressible water-impermeable material, the plate element having along one edge a re-entrant groove and along the opposed edge a complimentarily formed projection whereby one plate element being fitted into a slot in a wall may be mechanically interlocked with the next adjacent plate in the slot so as thereby to provide a continuous damp proof course.

2. A plate element according to Claim 1, wherein the re-entrant groove formed along one edge has a dovetailshape and the projection formed along the opposed edge has a complimentary dovetail-shape engageable in the corresponding groove of another plate element.

3. A plate element according to Claim 1 or Claim 2, wherein the thickness of the plate element is substantially equal to the thickness of a mortar course in a brick wall.

4. A plate element according to any of the preceding Claims, wherein the thickness of the plate element is in the range of from 10 to 15 mm.

5. A plate element according to any of the preceding Claims, wherein the plate element has a length of from 200 to 250 mm, and a width of from 200 to 250 mm.

6. A plate element according to claim 5, wherein the plate element is of a substantially square shape, when viewed in plan.

7. A plate element according to any of the preceding Claims, wherein the plate element is made of a relatively hard and durable material.

8. A plate element according to any of the preceding Claims, wherein the plate element is manufactured from a plastics material having very high crush resistant properties and virtually no flow or creep properties.

9. A plate element according to Claim 8, wherein the plate element is flexible to a slight extent, in the plane of its major surfaces.

10. A plate element according to Claim 8 or Claim 9, wherein the plate element is manufactured by a plastics moulding technique, a reinforcing material being incorporated in the plastics material during the moulding thereof.

11. A plate element substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.