Repairs: walls

When assessing the cause of cracks adopt a 'holistic' approach – view the crack as part of the whole building. For instance:

• Are parts of the building over-loaded down narrow masonry load paths (brick piers)?
• Or could the orientation of the building be causing wind suction or thermal expansion cracking on exposed southern/western aspects?

Note: Using 'telltales' to check whether a crack is ongoing is not always effective. Other options include resin-fixed screws around a crack (3 screws) measured, say, monthly using a vernier gauge can provide increments of vertical and lateral displacement across 2 planes. A spirit level can be used to provide a third measure of lateral displacement, but the accuracy may be limited unless there is room to use a long spirit level across the wall or the movement becomes very dramatic.

Solution 1 - Brick slips

Carefully cutting a matching brick to create a slip that can be glued in place across a cracked brick is probably the neatest way of repairing a damaged brick. The old damaged section needs to be carefully chased back, perhaps by partly drilling away. A matching mortar can be used to secure new to old. Use of a resin glue behind the slip is feasible if you are reasonably confident water will not be retained as a result.

Sometimes you can use an old brick from a sacrificial part of the building, so if you are carrying out alteration works, some careful salvage may pay dividends.

Solution 2 - Coloured mortar

This can provide a neat match but is really only suitable for small areas of repair; used over larger spans, colouring differences can start to show through, possibly later on as the mortar weathers.

Solution 3 - Stitch-in repair

Sometimes there is no alternative but to construct a whole new section of masonry let in as a repair.

Every endeavour should be made to match the brick finish and composition and mortar jointing, and to coordinate the brick sizes.

Differences between metric and imperial bricks may be small. Hopefully the repair will be there to look at for a long time, and a poor match can look disastrous and piecemeal. Several patch-in repairs can soon spoil the look of an entire building.