Repairs: walls

Details of calculations for the temporary support of vertical wall loads and working practices are set out in the excellent BRE Good Building Guides:

• GBG 10: Temporary support for openings in external wall: assessing loads (1992);
• GBG 15: Providing temporary support during work on openings in external walls (1992);
• GBG 20: Removing internal load-bearing walls in older dwellings (1999).

Needles or timber beams run through the wall and supporting the section above the area about to be repaired are normally fixed through the wall at 1m centres. However, be careful if the wall is old and the bonding between the bricks is too poor even to allow needling.

Cantilevered screw jacks reduce the need to support from both sides of the wall and improve working access. But you or the builder should double-check the load being applied to the jack to assess whether it is within safe working tolerances.

If it is a solid wall, you may be able to use steel channels to build up the lintel in 2 sections by supporting half the thickness of the wall and sliding in the channel section from each side, then bolting them together through the web. However, this requires very clean working to prevent debris from falling into the joint.

Temporary supports to walls:

(a) traditional 'needle' through support on screw jacks – reduces working access; load is spread across 2 points;

(b) cantilevered screw jack may provide much better access – vital to check that the wall above is well bonded and unlikely to buckle; check bearing for the prop (load concentrated in a small area).

Use of 2 steel channels to form a single beam, where working access or support proves difficult.