GB2621438A

GB2621438A - Cavity wall repair system

Info

Publication number: GB2621438A
Application number: GB2308177.1A
Authority: GB
Inventors: Mcginley Hugh
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-06-02
Filing date: 2023-06-01
Publication date: 2024-02-14
Anticipated expiration: 2043-06-01
Also published as: IE87473B1; GB2621438B; IE20220094A1; GB202308177D0

Abstract

A cavity wall repair system where the existing defective outer leaf of the original cavity wall is removed and an outer face 6 of an inner leaf 2 of the wall is then painted with a waterproof coating 7 such as bitumen. Spaced-apart rails 8 are mounted against the outer face 6 and are fixed to the inner leaf 2. Reinforcing elements 9 such as mesh panels, are mounted between and fixed to the rails 8. Shotcrete, or spray concrete, is then applied to the outer face 6 of the inner leaf 2 to encase the reinforcing elements 9 and is allowed to set to form a new outer leaf 10 of reinforced concrete. Insulation 11 is then fixed to an outer face 12 of the new outer leaf 10 and the insulation 11 is then covered by a façade panel 14 and the façade panel may be integral to the insulation layer.

Description

"Cavity Wall Repair System"

Introduction

This invention relates to a cavity wall repair system, in particular for repairing cavity walls in domestic dwellings and other buildings.

Background to the invention

The invention is particularly concerned with defects in building blocks which include mica which leads to cracks and other problems in buildings and homes constructed with the defective building blocks. Many homes have been constructed using concrete blocks that contain excessive amounts of mica. It would appear that building blocks with excessive amounts of mica attract moisture from the environment with external walls, in some cases, absorbing moisture from the ground like a sponge. The presence of mica affects the strength of the blocks, and they eventually crumble, seemingly after about five years. Whilst external walls are most exposed to the elements, internal walls are better protected, but not immune to problems. Walls get web-like cracking, crumbling blocks and plaster cracks, which in the early days look like minor subsidence or "settling". However, over time, many homes have vertical cracks close to the corners that extend from ground to roof. The damage eventually reaches a point where the building is no longer safe. One proposed solution is to demolish the existing building and replace it with a new building, constructed using safe building blocks. However, this is a relatively expensive and time-consuming process, and the residents of the building have to be displaced for a considerable amount of time. Further, it entails significant additional costs for temporary accommodation, furniture removal and storage etc. while the building is demolished and re-built.

The present invention is directed towards overcoming this problem.

Summary of the Invention

According to the invention, there is provided a cavity wall repair system for a cavity wall comprising an inner leaf and an outer leaf, the repair system comprising: removing the existing defective outer leaf, -2 -covering an outer face of the inner leaf with a waterproof coating, mounting a plurality of spaced-apart rails against the outer face of the inner leaf and projecting outwardly therefrom, supporting reinforcing elements on the rails, applying at least one layer of shotcrete to the outer face of the inner leaf and encasing the reinforcing elements, allowing the shotcrete to set to form a new outer leaf of reinforced concrete, and mounting insulation at an outer face of the new outer leaf with a facade panel on an outer face of the insulation.

In one embodiment of the invention, the system includes reinforcing a foundation beneath the wall.

In another embodiment, the foundation is reinforced by pressure grouting.

In another embodiment, the system includes re-supporting an existing floor or roof structure on the new outer leaf.

In another embodiment, the system further includes the steps of propping joists supported by the cavity wall prior to removing the outer leaf, mounting an extension shoe at an outer end of each joist for extending the joist outwardly of the inner leaf, and embedding an outer end of the extension shoe in the new outer leaf of reinforced shotcrete material.

In another embodiment, the waterproof coating is bitumen.

In another embedment, the system includes applying the shotcrete to the inner leaf in a number of layers having a thickness in the range 20mm to 30mm.

10 15 20 In another embodiment, the system includes applying the shotcrete to a depth in the range 80mm to 150mm.

In another embodiment, the system includes applying the shotcrete to a depth of 100mm.

S

In another embodiment, the reinforcing elements include mesh panels mounted between the rails.

Brief Description of the Drawings

The invention will be more clearly understood by the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a detail perspective cut-away view of portion of a wall repaired by the system of the invention; Fig. 2 is a detail perspective view of a joist extension shoe used in the system of the invention; Fig. 3 is a detail perspective view of the joist extension shoe, shown in use, mounted on a joist; Fig. 4 is another detail perspective view of the joist extension shoe, shown in use, mounted on a joist; Fig. 5 is another detail perspective view of the joist extension shoe, shown in use, mounted on a joist; Fig. 6 is a detail perspective view of portion of a building, showing a number of the joist extension shoes in use in accordance with the system of the invention; Fig. 7 to Fig. 12 are perspective views illustrating use of joist extension shoes in the system of the invention; Fig. 13 is a detail sectional plan view of a corner joint formed according to the system of the invention; -4 -Fig. 14 is an enlarged detail sectional view, showing detail XIV of Fig. 13; Fig. 15 is a detail perspective view illustrating a first stage in the formation of a corner joint according to the system of the invention; Fig. 16 is a detail perspective view illustrating a second stage in the formation of a corner joint according to the system of the invention; Fig. 17 is a detail sectional elevational view showing an eaves assembly formed according to the system of the invention; Fig. 18 is an enlarged detail perspective view, showing detail XVIII of Fig. 17; Fig. 19 is a detail perspective view of portion of the eaves assembly; and Fig. 20 is a detail elevational view of portion of the eaves assembly.

Detailed Description of the Preferred Embodiments

Referring to the drawings, a cavity wall repair system according to the invention will be described. Fig. 1 shows portion of a wall 1 repaired by the system of the invention. Typically, this wall 1 is one of the exterior walls of a house or other building, a similar repair being provided for all the external walls of the house or other building by the system of the invention.

Fig. 1 shows an existing inner leaf 2 of an original cavity wall 3 (Fig. 7) having the inner leaf 2 and an associated existing defective outer leaf 4 mounted on a foundation 5 after the defective outer leaf 4 of the original cavity wall 3 has been removed. An outer face 6 of the inner leaf is painted with a waterproof coating 7 of bitumen. A plurality of spaced-apart rails 8 are mounted against and fixed to the outer face 6 of the inner leaf 2 and project outwardly of the outer face 6 of the inner leaf 2. The rails 8 are substantially parallel and substantially vertical and are of C-section. A reinforcing mesh 9 is mounted on the rails 8. Shotcrete applied to the outer face 6 of the inner leaf 2 forms a new outer leaf 10 encasing the reinforcing mesh 9. The shotcrete can be built up in a number of layers to a total depth of about 100mm. When the shotcrete is allowed -5 -to fully set, it forms the new outer leaf 10 of reinforced concrete. Insulation panels 11 are mounted against an outer face 12 of the new outer leaf 10. These insulation panels 11 may conveniently be provided with an integral outer facade panel 14 or alternatively, an outer facade panel 14 of any suitable cladding may be affixed to an outer face of the insulation panels 11.

In accordance with the system of the invention the existing defective outer leaf 4 of the original cavity wall 3 is removed. The outer face 6 of the inner leaf 2 is painted with bitumen to provide a waterproof coating 7. The bitumen paint waterproof coating 7 acts as a temporary protection from rain as well as the water content present in the shotcrete application.

The rails 8 are mounted against the outer face 6 and are fixed to the inner leaf 2. Reinforcing elements, comprising mesh panels 9 are mounted between and fixed to the rails 8. The rails 8 comprise light gauge steel channels and act as guide rails for levelling the outer face of the shotcrete. The rails provide a mechanical connection between the inner leaf 2 and the new outer leaf 10. Conveniently, the rails 8 are spaced about 2.4 metres apart to accommodate standard size mesh reinforcement panels 9 mounted therebetween. Vertically spaced-apart central holes 15 in each rail 8 allow through passage of 12mm diameter reinforcing bars 16 for lateral continuity reinforcement. It will be noted also that spaced-apart starter reinforcement bars 17 project upwardly from the foundation to tie the new outer leaf 10 to the foundation 4. Also, existing wall ties 18, if useable, are retained and cast into the new outer leaf 10 to tie the inner leaf 2 and outer leaf 10 together.

Shotcrete is applied to the outer face 6 of the inner leaf 2 to encase the reinforcing mesh panels 9 and is allowed to set to form a new outer leaf 10 of reinforced concrete. Insulation panels 11 are then fixed to the outer face 12 of the new outer leaf 10. Conveniently these may include the outer facade panel 14 or any other suitable façade may be mounted at the outer face 12 of the new outer leaf 10.

Preferably, the system further includes reinforcing the foundation 5 by means of pressure grouting before forming the new outer leaf 10. To reinforce the foundation 5 the foundation 5 needs to be exposed. A plurality of PVC grouting nozzles of 130mm length and 10mm outer diameter, with a stopper at the outer end, are fixed on the -6 -foundation surface by drilling a hole of the same diameter and inserting each nozzle to a depth of about 80mm. Cement paste is used to fix and seal the sides of each nozzle. When fully sealed, after 24 hours, grouting can be carried out. Grout is prepared with mix of OPC and non-shrink grouting chemical. W/C ratio is maintained at not more than 0.45. Grouting is carried out at a pressure of 3 to 5 kg/cm using a grouting pump. Grout flows into the foundation 5, filling all the internal gaps in the foundation 5. The consumption of grout through each nozzle is recorded. Once the grout has completely set, the part of each nozzle extending outwardly of the foundation is removed, and the surfaced cleaned and smoothed.

Referring in particular to Fig. 4 to Fig. 12, the system includes using props 19 for propping joists 20 supported by the original cavity wall 3 prior to removing the existing defective outer leaf 4. A steel extension shoe 22 is mounted at an outer end 23 of each joist 20 for extending the joist 20 outwardly of the inner leaf 2 for embedding an outer end part 24 of the extension shoe 22 in the new outer leaf 10 of reinforced concrete material. The extension shoe 22 is generally channel shaped having a bottom wall 26 with upstanding side walls 27, 28. A divider plate 29 divides an interior of the extension shoe 22 into an inner part 30 for reception of the joist 20 and the outer end part 24. A centrally located upstanding rebar 32 in the outer end part 24 acts as a shear stud.

Voids 34 are provided in the bottom wall 26 and side walls 27, 28 at the outer end part 24 for improved bonding with the concrete of the new outer leaf 10.

The sequence for fitting the extension shoes 22 to the joists 20 is shown in Fig. 7 to Fig. 12. Fig. 7 shows the original cavity wall assembly. In Fig. 8, with props 19 supporting the joists 20, the existing defective outer leaf 4 has been removed. Fig. 9 and Fig. 10 show enlargement of the openings 35 in the inner leaf 2 which receive the outer ends 23 of the joists 20. Fig. 11 shows extension shoes 22 mounted on the outer ends 23 of the joists 20 with the outer end parts 24 projecting outwardly of the outer face 6 of the inner leaf 2. The enlarged openings 35 surrounding each joist 20 are filled with a compressible filler before the shotcrete is sprayed onto the outer face 6 of the inner leaf 2 to form the new outer leaf 10. After formation of the new outer leaf 10, as shown in Fig. 12, the outer end parts are embedded in the reinforced concrete new outer leaf 10 which now supports the joists 20.

Fig. 13 to Fig. 16 show a corner arrangement for joining two walls 1. A corner rail 40 -7 -having an inner flange 48 and an outer flange 49 extending outwardly therefrom at an angle of 135 degrees is attached by fasteners 41 to an inner leaf 2 of one of the walls 1 to receive abutting bevelled ends 42, 43 of the new outer leaves 10 of the walls 1. Vertically spaced-apart openings 45 in the outer flange 49 of the corner rail 40 allow for through passage of L-shaped rebar elements 47 to tie the adjacent ends 42,43 of the new outer leaves 10 together.

Fig. 17 to Fig. 20 show the mounting arrangement for an existing slate or tiled roof 50, with existing rafters 51, at a top of the wall 1. A stepped support plate 52, aligned with associated rafters 51, has an upper end 53 attached to an existing wall plate 54 on top of the inner leaf 2. Cut-out notches 56 at a top of the upper end 53 receive and allow through passage of rafters 51. A lower end 55 of the support plate 52 is attached to the outer face 12 of the new outer leaf 10 with an intermediate flange 57 seating on top of the new outer leaf 10. A second layer of mesh reinforcement 58 is provided at an upper end of the new outer leaf 10 within the new leaf 10. Several support plates 52 may be mounted end to end if required on top of the new leaf 10.

The terms "comprise" and "include", and any variations thereof required for grammatical reasons, are to be considered as interchangeable and accorded the widest possible interpretation.

The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail within the scope of the appended claims.

Claims

CLAIMS1. A cavity wall repair system for a cavity wall comprising an inner leaf and an outer leaf, the repair system comprising: removing the existing outer leaf of the cavity wall, covering an outer face of the inner leaf with a waterproof coating, mounting a plurality of spaced-apart rails against the outer face of the inner leaf and projecting outwardly therefrom, supporting reinforcing elements on the rails, applying at least one layer of shotcrete to the outer face of the inner leaf and encasing the reinforcing elements, allowing the shotcrete to set to form a new outer leaf of reinforced concrete, and mounting insulation at an outer face of the new outer leaf with a facade panel on an outer face of the insulation.
2. The repair system as claimed in claim 1, wherein the system includes reinforcing a foundation beneath the wall.
3. The repair system as claimed in claim 2, wherein the foundation is reinforced by pressure grouting.
4. The repair system as claimed in any one of claims Ito 3, including re-supporting an existing floor or roof structure on the new outer leaf
5. The repair system as claimed in any preceding claim, further including the steps of propping joists supported by the cavity wall prior to removing the outer leaf, mounting an extension shoe at an outer end of each joist for extending the joist -9 -outwardly of the inner leaf, and embedding an outer end of the extension shoe in the new outer leaf of reinforced shotcrete material.
6. The repair system as claimed in any preceding claim, wherein the waterproof coating is bitumen.
7. The repair system as claimed in any preceding claim, wherein the system includes applying the shotcrete to the inner leaf in a number of layers having a thickness in the range 20mm to 30mm.
8. The repair system as claimed in any preceding claim, wherein the system includes applying the shotcrete to a depth in the range 80mm to 150mm.
9. The repair system as claimed in any claim 8, wherein the system includes applying the shotcrete to a depth of 100mm.
10. The repair system as claimed in any preceding claim, wherein the reinforcing elements include mesh panels mounted between the rails.