Lime or cement mortar: getting repointing right on an old wall
Repoint a Victorian wall in the wrong mortar and you can do more harm than the weather ever would. Here is why the mix matters.
Mortar is meant to be the weak point
Good repointing works because the mortar is softer than the brick. Moisture that gets into a wall should evaporate out through the joints, and any movement should be taken up by the mortar cracking — not the bricks. Get the mortar harder than the brick and that logic reverses.
Why cement harms old walls
Pre-war walls were almost always built in lime mortar, which flexes and breathes. Repoint them in hard modern cement and moisture can no longer escape through the joints, so it exits through the brick faces instead — and when it freezes, the faces spall and crumble.
- Cement traps moisture that then damages the brick faces
- Hard joints concentrate movement into the bricks, cracking them
- Lime lets a wall breathe and flex as it was designed to
- Lime repairs blend better in colour and texture on period walls
Matching the original
The right repair copies what is already there. On a period wall that means a lime mortar matched for colour and a joint profile matched to the original. On a modern cavity wall built in cement, a matched cement mortar is correct. We work out which your wall needs at survey — like for like, every time.
Related questions
How do I know if my wall was built with lime mortar?
Age is the best clue — most homes built before roughly the 1920s used lime. The mortar is usually softer, lighter in colour and more crumbly than cement. We confirm it at survey before repointing.
Can cement repointing be reversed?
The cement can be carefully raked out and the joints repointed in lime, though it is slow work. It is far better to use the right mortar first time than to correct it later.
Ready to take it further? See our brickwork & masonry service.