If your home was built before the Second World War, there is a good chance its brickwork was laid in a lime based mortar. Repointing it with modern hard cement mortar is one of the most common, and most damaging, mistakes we see. Here is why it matters.
How a brick wall handles water
Every brick wall gets wet. In an older wall built with soft brick and lime mortar, moisture moves out through the mortar joints, which are softer and more breathable than the bricks. The mortar takes the wear, and every few decades it is raked out and repointed. The bricks themselves stay sound.
What happens with hard cement
Cement mortar is harder and less breathable than many older bricks. When it is used to repoint a soft brick wall, water can no longer escape through the joints, so it moves out through the face of the brick instead. In winter that water freezes and the faces of the bricks start to flake and crumble, which is known as spalling. The mortar survives and the bricks fail, the opposite of how the wall was designed to work.
How to tell what your home needs
- Age: many homes built before the late 1930s were built with lime based mortar.
- Brick type: soft, handmade or stock bricks usually suit a softer mortar.
- The existing mortar: original lime mortar is often softer and can be scratched more easily than cement.
Plenty of homes around Bexleyheath, Welling and Bexley were built in the 1920s and 1930s, right on the line between the two. That is why we look at every wall before deciding on the mortar.
What good repointing looks like
- Joints raked out to the right depth, not just skimmed over
- The right mortar for the brick, in a colour that matches
- A pointing style that matches the original
- No smears of mortar left across the face of the bricks
Find out more on our repointing and brickwork maintenance page, or send us a few photos for an honest opinion.