GB2144478A - Building repair system - Google Patents

Abstract

A system is proposed for repairing an Airey house in which the vertical support columns are defective. The system comprises building a blockwork wall (19) between the adjacent columns (3) and providing ties (21) in the form of shear connectors between the adjacent sections of blockwork on opposite sides of the columns. The connectors may be either a pin (21) passing through a hole drilled in the column and mating with adjacent blockwork or a fabricated bracket which fits around the column and locates in the blockwork. In either case vertical shear loads are transmitted between adjacent sections of blockwork. The system further proposes brackets for transferring the floor and roof loads carried by the joists to be transferred to the blockwork-thus, rendering the vertical columns redundant. The system further contemplates an external cladding which provides improved insulation and an attractive external appearance. <IMAGE>

Description

SPECIFICATION Building repair system The present invention relates to a building repair system and in particular to a method of repairing Airey houses.

Airey houses are made up of a plurality of parallel spaced apart vertical precast concrete columns with a steel reinforcing tube, to which are secured horizontal precast concrete panels to form an external wall. The horizontal panels are wired to the columns. The internal wall is formed by plasterboard secured to the columns. The floor and roof joists, typically steel girders, are bolted to the vertical columns.

Structural defects have been discovered in Airey houses, to the extent that the future of such houses has become questionable and there is a requirement for a system of repairing Airey houses which is economical and relatively simple to carry out in order to avoid having to demolish the houses and build new ones at many times the cost of repair. However, the repair systems proposed to date have been expensive to carry out as they virtually require the house to be rebuilt.

The structural defects have been caused in the main by moisture penetrating through the carbonated and/or cracked concrete of the supporting columns, causing corrosion of the hollow steel tube set inside each column. The net result is that the load bearing capacity of the columns is reduced.

Airey houses suffer from other problems namely; poor thermal insulation; damp and draught penetration through gaps in the precast concrete cladding; cold bridging at the position of each column; the non-existance of firestops, to compartmentallise the building in case of fire; bad condensation and relatively poor external appearance; which problems should ideally be rectified during repairs of the structural defects.

One known repair system requires the columns to be replaced one at a time, with a galvanised rolled steel section. This requires both the interior and exterior cladding to be removed with the associated disadvantage that the occupants must be moved out during the repair. Another known repair entails, removing the damaged section of column, usually the bottom few feet, and repairing using concrete enriched with silica materials which harden and water proof the concrete. The system has the disadvantage that it does not deal with the other defects in Airey house construction other than the structural defect.

Another known system requires a new brick work exterior cladding to be errected which requires the provision of additional foundations.

The present invention aims to provide a repair system which does not require additional foundations to be constructed or the columns to be repaired or replaced.

According the present invention then there is provided an Airey house repair system which comprises building up a blockwork wall between the vertical columns of the original house structure, and providing ties which interconnect the adjacent sections of blockwork wall on opposite sides of the columns to resist vertical she r movement between the adjacent sections of blockwork wall.

The provision of ties ensures that the structure possesses the necessary rigidity. Especially in respect of racking resistance In one embodiment, the tie comprises a horizontally disposed pin or the like which passes through a hole in the vertical column and extends from opposite sides thereof and is adapted to lie on the blockwork. The vertical columns are drilled to receive the pins which are preferably stainless steel. Preferably the free ends of the pins are bent into a wshape after positioning in the columns in order to provide a better bond with the grout securing the blocks together.

In an alternative embodiment, the tie comprises a fabricated bracket, having a channel shaped centre section adapted to fit around the vertical column, and oppositely directed horizontal wings between adjacent coarses which are adapted to lie on the blockwork on opposite sides of the column. The bracket is formed from sheet steel which is bent to shape. The wings have sufficient strength to resist the vertical sheer loads imposed thereon. The central section is not secured to the vertical column but is capable of vertical movement with respect thereto. Thus, the columns of blockwork are tied together and the columns can be rendered completely redundant.

The floor and roof loads are transmitted directly to the blockwork wall by providing respective brackets on the existing floor joists which co-operate with the layers of blockwork.

The existing connections of the floor and roof joists with the columns are disconnected.

A further feature may be the provision of a vertically extending bar which passes through the cavity in adjacent coarses of blockwork in the wall, and the introduction of concrete into the cavities to form reinforced blockwork. This improves the vertical bonding and reduces the likelihood of suckout i.e. movement of the blockwork wall inwardly or outwardly.

The system has the advantage that the erection of the blockwork only requires the outer concrete facing slabs to be removed and does not require the inner plasterboard facing to be removed. Thus, the repair can be carried out without serious disturbance to the interior of the house and if necessary the repair can be carried out whilst the building is occupied.

The blockwork is preferably specially made to a dimension which fits between the adja cent vertical columns and is of a light weight material with load carrying capabilities which allows the existing foundations to be utilized.

The above described features provide an effective structural repair to an Airy house.

The exterior of the blockwork is preferably finished with a system of interconnecting polystyrene boarding which is itself provided with an external treatment. This improves the insulation of the house as well as the external appearance.

The invention will now be described further, by way of example only, with reference to the accompanying drawings in which: Figures 1 and 2 show respectively a sectional elevation and a sectional plan of the basic Airey house construction before modification; Figures 3 and 4 show respectively a sectional elevation and a sectional plan of the Airey house constuction after modification; Figure 5 is a broken away perspective view illustrating the various components employed in a preferred repair system; Figure 6 is a diagramatic end view illustrating how the floor and/or roof beams are linked to the blockwork; Figure 7 is a perspective view of an alternative shear-connector in use and Figure 8 is a sectional plan view of the embodiment of Fig. 7.

Figs. 1 and 2 illustrate the basic construction of Airey house which is built on concrete ground slab 1. Spaced apart precast concrete columns 3 extend upwardly from the ground slab and have secured thereto by wire ties 5 precast concrete panels 7 which form the external wall of the house. The concrete columns are formed around steel tubes. The interior wall is formed by plasterboard and skim 9 secured to a timber backing 11. A vapour barrier 1 3 is preferably fixed behind the plasterboarding. The floor is formed by a sand and cement screed 1 5. The ground floor level 1 7 is below the level of the ground slab.

The columns are spaced at 450 cm. centres.

Figs. 3, 4 and 5 illustrate the modified structure in which blockwork 1 9 is fitted between the vertical columns 3. The blocks are made of a light weight material and dimensioned to fit between the columns. Alternatively, the blocks may be made smaller in width so that more than one block will fit between the columns-but this is less preferred. In order to provide the necessary rigidity to the structure tie pins 21 are inserted through holes drilled in the columns so that they extend horizontally therefrom and cooperate with the coarses of blockwork. This prevents slip occurring in the vertical direction between the columns and blockwork, and serves to transfer any loads from the columns 3 to the blockwork 1 9. An alternative embodiment of tie is described with reference to Figs.

7 and 8. Every alternate horizontal row of blocks is pravided with a tie (see Fig. 5). The ties are approximately 6 mm in diameter and made of a non-corrosive metal, eg. stainless steel or galvanized steel. The ties are straight initially and slotted through a close fitting hole, drilled through the column. After fitting, the tie is preferably deformed on each side of the column into a W-shape to assist its bond in the blockwork. The blockwork 1 9 is erected on the existing ground slab 1.

Referring to Figs. 7 and 8 there is shown an alternative shear connector 50. The connector comprises a central channel section having a front 52 and two sides 54 with the sides bent at right angles to the front. A respective wing 56 projects at right angles from each of the sides 54. The central section is adapted to fit around the vertical concrete columns of the original structure, whilst the wings 56 are arranged to lie on a coarse of the blockwork. In this manner, any vertical shear forces between the adjacent sections of blockwork 58, 60 are resisted by the shear connectors which are provided in every other coarse of blockwork. The bracket is free to move with respect to the vertical column so that in this embodiment no loading is transferred between the column and the blockwork.

As will be seen from Figs. 7 and 8, the blocks 62 have a single cavity 64 which extends through the block and which is filled with concrete. A vertical reinforcing bar 66 may be provided which extends through the cavities of adjacent coarses of blocks to improve the vertical bonding. Thus the reiforced blockwork effectively makes a vertical reinforced concrete column. The bar 66 is conveniently in 1 + m lengths with adjacent bars overlapping in the longitudinal direction to avoid weakness.

The other features of the repair system described herein are preferably employed with the alternative construction of shear pin described with reference to Figs. 7 and 8 i.e.

the external insulation system and the brackets for transferring the roof and floor loading to the blockwork.

Thus it will be seen that the blockwork can be built up without disturbing the inner plasterboard finish 9. The exterior cladding is removed to enable the blockwork to be erected. Whereafter a new external finish is applied comprising inter-connecting polystyrene boarding 23 which is secured in place using an adhesive 25.

An external covering 29 is applied over the polystyrene boarding 23. Preferably the external covering comprises a layer of mortar 27, a scrim layer 31, another layer of mortar 33 and a decorative finish 35-for example textured paint.

Where necessary any columns 3 which have broken away are made good with cement 37. A new damp proof layer 39 is laid on the ground slab and the block-work 1 9 is laid on this.

At floor and roof level, the existing joists, which comprise steel girders are bolted to the vertical columns. In order to ensure that the joist loading is transferred to the block-work it is proposed to attach L-shaped brackets 41 to the ends of these joists, which brackets rest on the block-work 19. Thus, support by way of the column is bypassed or supplemented.

New bolt holes 43 are provided for this purpose.

Thus, the system according to the present invention renders the existing columns redundant by installing specially designed loadbearing, light weight, insulating block-work between each column.

The poor thermal insulation is improved by firstly the incorporation of the insulative blockwork and secondly by the use of a full insulating system, applied to the outside of the house. Damp and draught penetration is stopped by the removal of the existing panels and by replacing them with a 'gap free' form of construction. Because of the solid and continuous construction of the new blockwork fire compartmentation of the building is automatically achieved. The condensation problem is resolved by the externally applied insulation system. The specific problem of the windows is solved by the complete removal of the existing windows and associated columns.

New windows to any design are built in with the new blockwork. Finally the appearance of the house is greatly enhanced by a new external finish.

The improvement work will be undertaken on sections of the building extending from floor to eaves level.

Three such 'panels' would be opened up on any one dwelling at any one time (one per elevation) and only when one panel was structurally sound would the adjacent cladding be removed. For example the sequence of operations may be as follows: 1. Remove all existing downpipes from the building and temporarily replace them with flexible hoses; 2. Break away the bottom precast concrete panel and remove off site; 3. Clean and prepare the bearing shelf of the foundation strip; 4. Carefully remove the remaining concrete panels in the section and take off site; 5. Carefully break away the base of any column that has totally defective concrete; 6. Apply liquid damp proof course to the foundation strip; 7. Drill through the existing columns in preset positions ready to receive the shear connectors; 8. Erect, lightweight, insulating, loadbearing blockwork between the columns.As this work progresses stainless steel shear connectors are incorporated through the predrilled holes in the existing columns; 9. At the same time as the blockwork is erected the existing columns are wire brushed clean and coated with a protective and adhesive cementitious slurry coat; 10. When the blockwork reaches first floor level the existing floor supporting bolts are modified and built into the new construction. a similar detail is utilized at eaves level to support the roof structure; 11.At the positions incorporating windows, the window, the window and columns are to be removed, leaving the internal lining intact; 1 2. The whole window area is rebuilt in blockwork using new double glazed windows and galvanised steel lintels; 1 3. In order to prevent further ingress of moisture into the inside of the steel tubes in each existing concrete column each one is to be pumped full of a modified cementitious grout, through a temporary injection tube at the base of each column; 14. Once the whole house has been made structurally sound with the new blockwork the insulative and decorative system is then applied. The walls covered with 50 mm thick, specially rebated and interlocking polystyrene boards, making sure that vertical joints are staggered.These boards are held in position by a special adhesive and also by nylon mechanical fixings into the new blockwork.

The corners and bottom edges are finished with metal beads or angles. A base coat of special mortar is then applied to the boards, incorporating a glass fibre scrim. A second coat is then applied and trowelled to a smooth finish. Finally, a decorative and protective texture coating is applied.

1 5. The downpipes are then replaced and the site is demobilised and left clear and tidy.

Because the new construction is virtually the same weight as that existing, no modifications are required to the foundation strip. The lateral stability of the house is maintained by the incorporation of shear connectors through the columns. The U value of the existing wall is approximately 1.2. The system described in this document would give a revised U value of approximately 0.45. The U values stated were calculated in accordance with C.l.B.S. Guide A3 Thermal Properties of Building Structures 1980.

As an alternative to the polystyrene board insulation system, an insulating coating containing polystyrene beads can be spray applied to the exterior of the blockwork to a depth of approximately 50 mm. The decorative finish is applied over the top of this. The depth of the spray applied insulation can be varied to give the required U-value.

Claims (9)

1. An Airey house repair system which comprises building up a blockwork wall be tween the vertical columns of the original house structure, and providing ties which interconnect the adjacent sections of blockwork wall on opposite sides of the columns to resist vertical shear movement between the adjacent sections of blockwork wall.

2. A repair system as claimed in claim 1 in which each tie comprises a horizontally disposed pin which passes through a hole in the vertical column and extends from opposite sides thereof and is arranged to lie on the blockwork between adjacent courses thereof, and wherein a plurality of said ties are spaced vertically along the length of each column.

3. A repair system as claimed in claim 1 or 2 in which the pin is deformed after positioning in the column to provide an improved bond with the grout securing the adjacent courses of block together.

4. A repair system as claimed in claim 2 or 3 in which the pins are made of stainless steel.

5. A repair system as claimed in claim 1 in which each tie comprises a bracket which is adapted to fit around the vertical column and having two substantially horizontal wing portions adapted to lie on the blockwork on a respective side of the vertical column.

6. A repair system as claimed in claim 5 in which the bracket is fabricated from sheet metal.

7. A repair system as claimed in any of claims 1 to 6 further comprising respective brackets secured to the roof and/or floor joists and abutting the blockwork for transferring roof and/or floor loads to the blockwork.

8. A repair system as claimed in any preceding claim comprising an external cladding secured to the exterior of the blockwork, which external cladding comprises an insulating layer.

9. A repair system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.