GB2165576A - Method of repairing a house - Google Patents

Abstract

A method of repairing a house (eg Orlit house) having three main frames 1, 2, 3 connected by secondary beams 4, all made of prefabricated reinforced concrete, comprises removing the original secondary beams and replacing them with new timber beams 8 running essentially at right angles to the direction of the original beams. Support for the new timber beams 8 is provided by a pair of steel joists 10 running perpendicular to the direction of the new beams 8. The outside walls of the house are repaired by removing the outer leaf whilst retaining the inner leaf 7 intact, connecting to this inner leaf 7 a new block work wall 13, and then facing the new block work wall 13 with a brick work cladding 16. Insulation material 14 and a cavity 15 are provided between the block work wall 13 and the cladding 16. <IMAGE>

Description

SPECIFICATION Method of repairing a house The present invention relates to a method of repairing a house, and in particular houses which are mass-produced system built houses.

The type of house to which the present invention relates is a house having its main structural elements either pre-castfrom concrete, or poured in-situ again using concrete or similar material. In the case of houses known as ORLIT houses, the main structural elements are made from prefabricated reinforced concrete. Other houses, known as NOFINES houses have their main structural elements constructed in-situ by pouring a mixture of pebbles and cement. In these types of houses, it was common practice to construct the house so that the floor beams supporting the first floor extended from one side of the house to the other, in the same direction as the roof, and were themselves supported by the main structural elements of the side walls of the house.

A typical house of this type comprises three main frames, each having two outer columns and an inner column which together support a horizontal beam.

Two such frames are located one on each side of the house, and the third is located centrally between the two outer frames. Each frame typically extends to the top of the ground floor, and a further set of frames may be provided at first floor level. The columns of these frames are typically made of 6 inch by 6 inch (15.2 cm x 15.2 cm) prefabricated reinforced concrete, and are joined together by secondary beams, again made from prefabricated reinforced concrete, and 7 inches deep by 3 and a half inches wide (17.8 cm x 8.9 cm).

Since these houses were built, it has been discovered that all concrete suffers an ageing process which results in chemical changes within the material. These changes have an adverse effect on the steel reinforcement which provides most of the strength of the reinforced concrete. The process is one of carbonation of the concrete in which carbon dioxide in the atmosphere reacts with the concrete to reduce its alkalinity. Eventually this process results in the rusting of the embedded steel reinforcement, and the consequent expansive forces tend to crack the concrete. This is a particular problem in houses of this type, built in the 1950's, when only half an inch of concrete covering the steel reinforcing was required. Now this requirement has been increased to one to one and a half inches in order to provide increased durability.

A further problem has been created by the addition of calcium chloride to the concrete mix in order to mane the concrete harden more quickly. Subsequently, it was discovered that this chemical further aggravates the problem of rusting of the steel, so that steel has been known to rust severely in concrete which is otherwise of good quality.

The reinforced concrete columns of the main frames of the house are such that the reinforcing steel is not unduly close to the surface. In general these columns are still reasonably sound, and if they remain dry, rusting should not take place.

However, the horizontal secondary beams include in-situ concrete connections between their sections.

Such in-situ joints were often made with high alumina cement in order to give accelerated hardening. This type of cement degenerates much faster than ordinary cement, and in damp conditions over a period of 20 years or so, the material may be quite useless. Furthermore, the amount of calcium chloride used in the secondary beams was often quite high. Altogether these secondary beams are highly prone to deterioration.

This type of house also has outside walls which comprise inner and outer leaves, also made from concrete, typically in the form of large panels. The outer leaf is lightly reinforced and the reinforcement is too close to the surface. As a result, the concrete may relatively rapidly deteriorate to the depth of the reinforcement in many places.

According to the present invention there is provided a method of repairing a house having two or more main frames spanned by a plurality of secondary beams which support a floor, said secondary beams extending from one side of the house to the other, the method comprising removing the original secondary beams spanning the main frames and installing new secondary beams which extend from the rear of the house to the front.

Thus, by replacing the original secondary beams supporting the floor with new secondary beams running essentially at right angles to the direction of the original secondary beams, the main frames are unloaded and the defective original secondary beams are removed.

Preferably, the new secondary beams are supported by steel joists extending between the columns of the main frames.

Preferably, the columns of the main frames are modified by constructing around them piers of brick work to seat the steel joists.

Preferably, the outside walls of the house are repaired by removing the outer leaf whilst retaining the inner leaf intact, and replacing the inner leaf by a structural concrete block work wall which is then clad on the outside with facing bricks.

Thus, the structural function of the main frame in a gable end wall is taken over by the new block work.

The roof loads in the front and rear walls of a house will also be taken by the new block work.

An embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings in which-: Figure 1 shows the main structural elements of an existing ORLIT house; Figure 2 shows a principle section through an ORLIT house prior to repair according to the present invention; and, Figure 3 shows a principle section through the house shown in Figure 2, after repair according to the present invention.

An embodiment of the present invention will now be described with reference to an ORLIT house.

Referring to Figure 1, an ORLIT house comprises three main frames, indicated generally by 1,2 and 3.

Main frame 1 is located within the gable wall, frame 2 crosses the middle of the house, and frame 3 is located within the party wall. Each frame comprises two outer columns 1 a, 1 c and an inner column 1 b, all made of prefabricated reinforced concrete. Each frame extends to the top of the ground floor, and a further set of frames may extend from first floor level to the roof.

Each of the main frames 1,2 and 3 are joined together by secondary beams 4 which span the main frames at first floor level, running from the gable wall to the party wall. The secondary beams 4 support the floor 5 of the house, as well as the walls, roof and live loads, as shown in Figure 2. The secondary beams 4 are also made of prefabricated reinforced concrete which is generally in very poor condition as previously explained.

The outside walls of the house comprise an outer cladding leaf 6 and an inner leaf 7. The internal leaf 7 is of clinker block which is generally found to be in good condition. The blocks are plastered and decorated on the inside and therefore there is an additional incentive to leave this inner leaf intact.

However, the outer cladding 6 is generally in poor condition, as explained previously.

Referring now to Figures 2 and 3, a method according to the present invention comprises removing the original secondary concrete beams 4, and installing replacement timber beams 8 which run essentially at right angles to the direction of the original secondary beams.

The existing first floor comprises 1 inch (2.5 cm) thick tongued and grooved timber floor boards 5a nailed to 3 inch by 2 inch (7.6 cm x 5.1 cm) timber beams 5b which are carried by the reinforced concrete secondary beams 4 running at right angles to the timber beams and in the same direction as the floor boards. These secondary beams 4 are removed and replaced by new timber beams 8 which span in the same direction as the timber beams 5b supporting the floor boards.

A number of 2 inch by 2 inch (5.7 cm x 5.1 cm) timber transverse bearers 9 are introduced at right angles to the existing timber beams 5b. Underneath these timber bearers 9 the new timber beams 8 may be positioned at centres appropriate for direct fixing of the plasterboard underneath. To enable this repair to be carried out, eitherthefloorboards orthe plasterboard are removed. In a preferred embodimentthe plasterboard is removed, access being gained from a downstairs room.

Since the new secondary beam 8 cannot span the complete depth of the house from the rear wall to the front wall to the front wall, support is provided by means of a pair of steel joists 10, one spanning the party wall column to the central column, and another, slightly lower, to pass under and support the existing staircase, spanning the central column to the gable column. To support the steel joists 10 without relying on the column, piers of brickwork 11 are built around the existing columns in the ground floor to seat steel joists 10.

The existing cladding panels 6 on the outside walls are removed, as are the existing windows, and the precast concrete window surrounds 12. The internal leaf 7 is connected to and reinforced by a new 100 mm thick concrete block wall 13 which is bonded to the existing block work 7. Insulation material 14 is placed outside the line of the new block work and a cavity 15 is left between the insulation and a new external leaf 16 of facing bricks. To all intents and purposes, the new wall is eqivalentto a modern construction using traditional materials.

The use of the load bearing block work 13 as an inner leaf of the new outer wall enables the structural function of the frame in a gable end wall to be taken over by the new block work wall. However, the frame is left in position to avoid the extensive damage to the house which would be caused by its removal. The roof loads in the front and rear walls will be taken by the new leaf of block work, and alternative support is provided for the ends of ceiling joists bearing upon the central frame.

In a preferred embodiment, the in-situ stitches in the construction of the ground floor beam component of the frame are cut out and the suspended reinforced concrete portion of this frame is removed.

In the roof space, all loads are removed from the frame. The main frame members are left intact but protected against water ingress. They will, in the modified construction, carry only their own dead weight. The main frame 3 is combined with the party wall and here again the frame is unloaded by the modifications for supporting the floor, and the frame components are left in place.

A particular advantage of the present invention is achieved in the case of terraced houses, in which a house which undergoes a repair according to the present invention may be effectively isolated from its two neighbouring houses by the reversal of the secondary beams as described above.

Claims (6)

1. A method of repairing a house having two or more main frames spanned by a plurality of secondary beams which support a floor, said secondary beams extending from one side of the house to the other, the method comprising removing the original secondary beams spanning the main frames and installing new secondary beams which extend from the rear of the house to the front.

2. A method according to claim 1 in which the new secondary beams are supported by steel joists extending between the columns of the main frames.

3. A method according to claim 2 in which the columns of the main frames are modified by constructing around them piers of brick work to seat the steel joists.

4. A method according to any of the preceding claims in which the outside walls of the house are repaired by removing the outer leaf whilst retaining the inner leaf and replacing the inner leaf by a structural concrete block work wall which is then clad on the outside with facing bricks.

5. A method of repairing a house substantially as herein described with reference to the accompanying drawings.

6. A method according to claim 1 and substantially as herein described.