It can. On older solid stone or soft brick walls, a hard cement render can crack and let rain in behind it, then stop the wall drying out, so moisture builds up and shows as damp inside. Breathable lime render is often more suitable for those walls, but each wall should be assessed.
A lot of older Yorkshire houses had their stone or soft brick rendered in sand and cement at some point, often to cover up poor pointing or to stop damp. Sometimes it’s still doing fine. Often, decades later, it’s part of the problem.
Why hard render and old walls don’t always mix
Older solid walls were built to get wet and dry out again. Rain soaks into the outer face, then evaporates back out when the weather improves. Lime mortars and renders allow that. Cement render is harder, more rigid and much less vapour-permeable. Two things go wrong:
- It cracks. Old walls move slightly with temperature and moisture, and rigid cement render develops fine cracks, especially around windows and at corners.
- It traps water. Rain gets in through the cracks and behind the render, but it can’t evaporate back out through the dense render. So the wall behind gets wetter and wetter.
Inside, you see damp patches on external walls, sometimes at any height, plus salts and blown plaster. Outside, look for cracks, hollow-sounding render when tapped, bulging sections, staining, and render carried down over the DPC to the ground.
Isn’t render meant to keep damp out?
A good render on the right wall, properly detailed, does. The details matter: it should stop above the DPC with a bellcast so water drips clear, and it needs maintaining. The problem is the wrong render on the wrong wall, or render that’s failed and nobody’s noticed.
What to do
- Have the render inspected, including tapping it for hollow areas.
- Repair cracks and failed sections. Small, sound areas may just need maintenance.
- Make sure it isn’t bridging the DPC at the bottom.
- On solid older walls where the render has failed badly, removing it and re-rendering in lime, or leaving the masonry exposed and repointing correctly, is often the better long-term answer. It needs care, because taking hard render off can damage soft brick or stone.
Removing render is a big job. Don’t do it just because you’ve read cement is bad. Make sure it’s actually the cause of your damp first.
When to call a specialist
If you have damp on rendered walls and suspect the render, get it inspected before spending money on internal damp treatments that won't solve it. Book a survey with All Dry on 01226 287181 or email info@alldrydampproofing.com.
Frequently asked questions
Is lime render better than cement render?
On older solid walls lime is often more suitable because it is more breathable and flexible, but it depends on the wall.
How do I know if my render is failing?
Look for cracks, hollow-sounding areas when tapped, bulges and staining.
Should render go down to the ground?
No, it should stop above the DPC with a bellcast so it doesn't bridge it.