GB2278863A - Repairing building structures - Google Patents

Abstract

A method of repairing a Unity house structure comprises the steps of: excavating beneath a ground floor slab 8; removing infilling below the slab; inserting at least one support beam 16 under the slab; and hard packing the beam into place. The method is of particular utility where loose or compressible infilling has been used in the original construction of the Unity house. <IMAGE>

Description

METHOD The present invention relates to a method of repairing building structures.

In some forms of houses and other buildings, the structure above the ground is supported wholly or partially by load bearing columns which extend through a floor slab.

Around the periphery underneath the ground floor slab, where earth was excavated for laying the foundations, is infilling. The ground floor slab is thus supported in its middle by packed earth, and at its periphery by infilling.

The ground floor slab in turn supports exterior wall panels along some or all of its periphery. The panels cover up the internal building structure, including the columns, and there is a cavity between the exterior panels and the internal leaf of the overall wall structure.

Constructions of this type are typically found in a structure commonly called a Unity (TM) house. The term "Unity house" will, for convenience, be used herein to denote such a structure.

A problem with such constructions is that the infilling may be loose or, with time, the infilling tends to become more compressed or to be displaced into cavities in the surrounding sub-soil. This is a particular problem if poor quality infilling has been used, for example broken bricks, or glass, and it results in the periphery of the ground floor slab receiving inadequate support. There is also a risk of corrosion damage to the supporting columns where they are only protected by loose infilling.

The lack of adequate support for the ground floor slab causes it to sag at its periphery and may result in its fracturing in places. Support for the exterior wall panels may also be inadequate, and this may be exacerbated by any sagging of the ground floor slab. Furthermore, the lower or lowest exterior wall panels tend to deteriorate as a result of the weight of the panels bearing down on a small supporting base.

Typically the exterior wall panels in a Unity house are made of concrete; however the invention is not limited to the repair of houses with concrete exterior wall panels and may be applied to buildings with exterior wall panels which are constructed of other materials.

The present invention also provides a method for repairing a Unity house, the method comprising the steps of: excavating adjacent to the side of the ground floor slab to be supported; removing sufficient infilling below the ground floor slab to create a gap sufficient to permit the insertion of at least one support beam; inserting at least one support beam between the foundations and the floor slab so as at least in part to bridge the gap; hard packing the beam into place.

The term "hard packing" is used herein to denote the action of filling the vertical gap between a support beam and the ground floor slab with cement, grout, or other suitable packing material, and compressing that material so that it will carry a load imposed by the weight of the ground floor slab without substantial further compression. Use of the term as a noun should be similarly construed.

As well as supporting the ground floor slab, the new support beams may protect the feet of the columns from corrosion better than the loose infilling does.

If damaged, it is preferred that the lowest ground floor exterior panels are replaced by the steps of: providing means for supporting the panels above the lowest ground floor exterior wall panel; removing the lowest ground floor panel and fixing a new exterior panel.

The new exterior wall panel is preferably shaped so that the average area of its footprint is substantially greater than the average area of its upper edge, so that the load caused by its own weight and the weight of other panels bearing down on it is spread out to minimise damage to the panel and the ground floor slab.

Preferably the support beams and the new exterior panel are pre-cast and made of concrete.

Preferably each support beam is provided with a substantially longitudinal bore, and the beams are arranged under the ground floor slab so that the bores are in register with one another and a reinforcing element may be passed through all the individual beam sections and grouted in place to impart greater rigidity and strength to the structure.

Preferably the reinforcing element is made of steel.

When two adjacent sides have been repaired as described above, they may be joined together by means of a corner piece. The corner piece may be pre-cast or, preferably, constructed in situ.

Preferably any brackets that fix the exterior panels to the columns are replaced if damaged, and any unsound parts of the columns and/or slab are repaired prior to the fixing of the new exterior panel.

It is preferred that after repairing unsound parts of the columns and slab, the cavity is cleared of loose material and a new damp proof membrane is put in place to form a cavity tray and to protect the columns.

After completing the replacement of the ground floor exterior panel, the building may be re-pointed if necessary.

The invention will now be further described, by way of example, with reference to the following drawings in which: Figure 1 is a vertical section of a Unity structure before treatment according to the present invention; Figure 2 is an elevation view of a Unity house in accordance with the present invention; Figure 3 is a plan section along line A-A of Figure 2; Figure 4 is a plan section along line B-B of Figure 2; Figure 5 is a vertical section along line C-C of Figure 2, which is along a similar line to that of Figure 1.

Figure 1 shows a Unity house prior to repair by the present method. The edge of the ground floor slab 8 is inadequately supported by the infilling 28, causing it to tend to sag and become damaged; the exterior panel 6a overhangs the ground floor slab 8. The weight of one or more panels 6a bearing down on the relatively small area of contact with the slab 8 tends to cause damage to the foot of the panel 6a and the slab 8. The damage to the ground floor slab 8 and to the adjacent exterior panel 6a is further promoted by relative movement of the slab 8 and the panel 6a as the infilling 28 is redistributed.

Figure 2 shows a Unity house which has been repaired in accordance with the present invention. Supporting concrete columns 2, 4 are fixed by grouting into the foundations 14; they pass through a ground floor concrete slab 8. Loose infilling beneath the periphery of the slab 8 has been removed and replaced by a support beam 16, made of pre-cast concrete, which is sat upon a grout bed 12 on the foundations. A hard packing layer 10 has been inserted between the support beam 16 and the bottom of the slab 8, so that the beam 16 indirectly supports the edge of the slab 8.

A new exterior concrete panel 6 overlies the edge of the slab 8, and this is affixed to the columns 2, 4 by means of brackets 18.

Figure 3 shows how the new panel 6 is attached to the bracket 18 by means of a bolt 20. Figure 3 also shows how the foot of the panel 6 is wider than its top edge, thus distributing the weight load of the panels over a greater area of the floor slab 8.

Figure 4 shows the support beam 16 fitted under the slab 8 and around the columns 2, 4. Longitudinal bores 22 pass through the support beams 16, and holes have been drilled in the columns 2, 4. The support beams 16 have been reinforced with steel bars 23, located in the bores 22, which pass through the beams 16 and the columns 2, 4. Inclined grout holes 24, 26 permit cement grout to be introduced into the bores 22 to secure the steel bars 23 within the bores 22 and columns 2, 4 to produce a rigid support structure. The loose infilling 28 is removed and the resulting void filled with grout.

Figure 5 shows more clearly how the load is spread out at the foot of the new panel 6. A new bracket 18, has been provided to affix the new panel 6 to the column 2. A new damp proof membrane 30 has been added between the two leaves of the wall construction. Reinforcing steel bars 23 have been grouted in to the longitudinal bores 22 of the pre-cast concrete support beam 16, using cement grout.

Although the present invention has been illustrated, for simplicity, by reference to the use of concrete structures with steel reinforcement, the invention is not limited to this embodiment. Any suitable structural materials may be used provided that they have sufficient structural stability and weather resistance. For example, the exterior cladding panels could be made from wood, plastics, or ceramic materials without departing from the scope of the invention.

Although the present invention has been described in terms of the repair of Unity houses, the invention is not limited to Unity houses, but may be applied to other structures with inadequately supported ground floor slab edges.

Claims (10)

1. A method for repairing a Unity house as hereinbefore defined, the method comprising the steps of: excavating adjacent to the side of the ground floor slab to be supported; removing sufficient infilling below the ground floor slab to create a gap sufficient to permit the insertion of at least one support beam; inserting at least one support beam between the foundations and the floor slab so as at least in part to bridge the gap; hard packing the beam into place.

2. A method as claimed in claim 1, comprising the further step of replacing damaged lowest ground floor exterior panels by: providing means for supporting the panels above the lowest ground floor exterior wall panel; removing the lowest ground floor panel, and fixing a new exterior panel.

3. A method as claimed in claim 2, wherein the new exterior wall panel is shaped so that the average area of its footprint is substantially greater than the average area of its upper edge, so that the load caused by its own weight and the weight of other panels bearing down on it is spread out to minimise damage to the panel and the ground floor slab.

4. A method as claimed in any one of the preceding claims, wherein the support beams are pre-cast and made of concrete.

5. A method as claimed in claim 2 or claim 3, wherein the new exterior panel is pre-cast and made of concrete.

6. A method as claimed in any one of the preceding claims, wherein each support beam is provided with a substantially longitudinal bore, and the beams are arranged under the ground floor slab so that the bores are in register with one another and a reinforcing element may be passed through all the individual beam sections and grouted in place to impart greater rigidity and strength to the structure.

7. A method as claimed in any one of the preceding claims, wherein two adjacent sides are repaired and joined together by means of a corner piece.

8. A method as claimed in any one of the preceding claims, including the further steps of putting a new damp proof membrane in place to form a cavity tray and to protect the columns.

9. A Unity house which has been repaired by the steps of: excavating adjacent to the side of the ground floor slab to be supported; removing sufficient infilling below the ground floor slab to create a gap sufficient to permit the insertion of at least one support beam; inserting at least one support beam between the foundations and the floor slab so as at least in part to bridge the gap; hard packing the beam into place.

10. A method of repairing a Unity house substantially as hereinbefore described with reference to and as shown in the drawings.