How to Patch a Hole in a Brick Chimney

Cracks and holes in the bricks or in the mortar between the bricks are some tell-tale signs that your chimney is becoming damaged. Patching cracks and holes in the brick of a chimney can save you thousands of pounds worth of repairs down the line, along with reducing your risk of chimney fires at home.

Roof Safety:

Patching holes in your chimney will involve working on the roof, where there is always a potential for falls and serious injury. Be sure to work on a dry day and wear shoes or boots with firm-grip soles. Make sure that you have all the appropriate safety equipment for working on a roof including a safety harness and a hard hat to reduce your risk of accidents and injury.

Patching Cracks or Holes in Bricks:

Individual chimney bricks that have cracks or holes in them can be repaired with mortar. Begin by cleaning out the hole or crack with the edge of a putty knife or screwdriver, before cleaning it thoroughly with a stiff wire brush. Use a trowel or a caulking gun to fill the crack or hole with the mortar. If you want the filled areas to match the rest of your chimney, you can mix brick dust into the mortar when making up the mixture. Pressing a brick onto the mortar when it is still wet will ensure that it dries with the same texture as the rest of the bricks.

Replacing Bricks:

Bricks that have large holes in them or are severely cracked are best removed and completely replaced. It is possible to remove a single brick from your chimney carefully without affecting the adjoining bricks. Slowly chip away the mortar from around the brick using a masonry chisel. You can also use a drill with a masonry bit to bore holes into the mortar and speed up the process. Once the brick has been loosened, gently pull it out by hand before using your chisel to remove any residual mortar from the adjacent bricks until they are smooth. Then, apply mortar to all four sides of the replacement brick before pushing it in place. Centre it to ensure that the seam on each side is of equal width, before removing any excess mortar and using a tuckpointing tool to smooth the joints.

Cracks and holes in the bricks of a chimney can lead to water getting through into the roof space and can also increase the risk of chimney fires. It is best to have these jobs done by a professional if you do not have the right safety equipment for working at height.