Why lime render, not cement?
A rendered solid wall works like a coat, not a raincoat. Lime render absorbs some rain during weather and releases it again as vapour when the sun and wind return — keeping the wall behind it dry over the annual cycle. Cement render does the opposite: it is hard, brittle and impermeable. It cracks as the building moves, rain is driven in through the cracks, and the cement then traps that water inside the wall.
The result is familiar to anyone who owns an older rendered house: damp patches inside, blown render outside, spalling stone and rotten lintels behind. Much of our rendering work starts with carefully removing a failed cement render and undoing the damage it caused.
Our lime rendering service
- Full lime render systems — scratch, straightening and finishing coats — on stone, brick and cob
- Careful removal of failed cement render and substrate repair
- Napped, floated and roughcast (harling) finishes to match local tradition
- Insulating lime render and cork-lime systems for external thermal upgrades
- Limewash and breathable silicate paint finishes in traditional colours
- Repairs to existing lime render — patching and re-finishing rather than wholesale replacement where possible
How we specify a lime render
Exposure decides the mix. A sheltered brick elevation and a west-facing gable in the Welsh valleys need different renders. We match the strength of the render to the substrate and the exposure — typically natural hydraulic lime (NHL 2 to 3.5) with well-graded sharp sand, applied in two or three coats, each weaker than the one beneath it so the system stays flexible and sacrificial. Hair or fibre reinforcement is added where the background demands it.
Curing is managed, not left to chance: fresh lime render is protected from sun, wind and frost with dampened hessian, and each coat is given time to carbonate. It is slower than cement — and it is why lime renders last for decades instead of cracking in the first winter.
Can you render over cement render?
Applying lime over sound cement is rarely the right answer — the cement underneath goes on trapping moisture, and the lime above it cannot fix that. Where a cement render has failed on a solid-wall building we almost always advise removal back to the masonry, repair of the joints and faces, and a full breathable system from the wall out. We assess each case honestly; where removal risks doing more harm than good, we say so.
Where we work
Lime rendering across South Wales and the West — Newport, Cardiff, Monmouthshire, Abergavenny, Hereford, Gloucester, Bristol and Swansea. Scaffold-dependent external work is planned around the seasons: spring to autumn is the lime rendering window, and diaries fill early.