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Damaged Brickwork At The Bottom Of A Wall
The lowest courses of brick are eroded, crumbling or missing their faces while the wall above is sound.
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What's happening?
Damage that stops at a clear height above the ground is telling you something specific. The bottom of a wall is the wettest and slowest-drying part of it, because rain splashes back off the paving, ground moisture is close by, and the sun rarely reaches it. Approved Document C expects the damp proof course in an external wall to sit at least 150mm above the adjoining ground precisely so this zone stays above the wet. Where paving, soil or tarmac has been raised over that line, the bricks below it are permanently damp and carrying ground salts, and they break down from frost and salt crystallisation while the identical brick a metre higher stays perfect. A tide mark of damage is therefore a levels problem far more often than a brick-quality problem.
What usually causes it?
- Paving, path or driveway raised over the damp proof course so the lower courses stay wet
- Soil, gravel or a raised bed banked against the wall holding moisture and salts against the brick
- Rain splashing back off hard paving laid tight to the wall with no gravel margin or channel
- De-icing salt used on an adjacent path or drive, crystallising inside the bricks
- Facing bricks used below ground level where an engineering or frost-resistant brick was needed
- A blocked or missing gully or channel so surface water ponds against the wall
- Cement render or pointing carried down to the ground, trapping moisture in the lowest courses
Is it dangerous?
Progressive rather than sudden. Deep erosion of the lowest courses does reduce the wall's effective thickness at exactly the point carrying the most load, which matters on a single-skin wall, a bay or a porch. More commonly it is the damp consequence: brickwork saturated above the damp proof course line bridges it, and moisture then reaches the internal plaster and any timber built into the wall. On a house with a suspended timber floor, permanently wet lower courses often come with blocked vents as well, which is the combination that decays joist ends.
Can I fix it myself?
The cause, often, and that is the half that matters. Find the damp proof course — usually a visible line of slate, bitumen or engineering brick in the joints — and check whether the ground outside sits below it. If soil or gravel has crept up, dig it back and keep a clear margin. Where paving is the culprit, lifting a row of slabs next to the wall and replacing them with a gravel channel is realistic DIY and cures a surprising number of cases. Do not render or paint the damaged courses to tidy them up: that seals the moisture in and hides the erosion continuing behind it.
When should you call a bricklayer?
Call a bricklayer where brick faces have gone rather than merely weathered, where the erosion is deep enough to see into the wall, or where courses need cutting out and replacing. Call a builder where paving or a driveway has to be lowered or a drainage channel formed, and where the damp proof course itself has been built over and needs reinstating. If plaster inside has blown along the same wall, expect that to be part of the same job.
What will the bricklayer actually do?
- Locate the damp proof course and measure the finished ground level against it before repairing any brickwork
- Cut out and replace eroded bricks with frost-resistant units suited to a wet, low-level position
- Repoint the lower courses in a mortar weaker than the brick so the joints stay sacrificial
- Reinstate or bypass a bridged damp proof course so it is doing its job again
- Form a gravel margin, channel or drainage detail so paving no longer holds water against the wall
- Remove cement render or pointing carried down to the ground where it is trapping moisture in the wall
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