Glossary
Render on London houses: planning, damp and detailing
External wall coating (often stucco in white-painted London terraces).
External wall coating (often stucco in white-painted London terraces).
Render is a wall finish applied in coats over masonry. On a modern cavity wall a cement or polymer render is normal; on a solid historic wall the correct material is a lime render, because a cement render traps moisture and drives damp into the brickwork behind it.
On an unlisted house outside a conservation area, cladding or rendering an exterior wall is permitted development under Class A provided the materials are similar in appearance to the existing house — which rendering a brick house is usually not, so in practice an application is often needed.
In a conservation area, on Article 2(3) land and where an Article 4 direction applies, the right to clad or render is withdrawn outright. On a listed building it requires listed building consent.
Solid brick, stone or cob: lime render, typically NHL 3.5, applied in two or three coats with each coat weaker than the one beneath, finished with a limewash or mineral paint. Modern blockwork or a cavity wall: sand-cement, monocouche or a polymer-modified system on a mesh.
Applying a cement render over solid brick is the single most damaging common retrofit in London housing stock. It cracks, water gets behind it, and it cannot get out.
EWI systems are rendered finishes over insulation board. On a solid wall they can reach the 0.30 W/m²K threshold value or better, but they change the external appearance, bury the reveals and eaves details, and almost always need planning permission in a conservation area. Breathability of the whole build-up needs checking against BS 5250.
Render in a Greenwich context: Royal Borough of Greenwich (Greenwich Council) runs 20 conservation areas including the Greenwich Town Centre (World Heritage Site) Conservation Area and the Blackheath Conservation Area, and there is no borough-wide Article 4 direction, so permitted development generally survives outside conservation areas. That decides how render is handled: £548 and 8 weeks for a Greenwich householder application, or £274 for the Lawful Development Certificate that records render as lawful. The law behind render sits in the Town and Country Planning Act 1990, the GPDO 2015 and the Building Regulations 2010.
| Historic walls | Lime render, NHL 3.5 |
|---|---|
| Modern walls | Sand-cement, monocouche or polymer |
| Coat rule | Each coat weaker than the one beneath |
| Conservation area | Permitted development withdrawn |
| Listed building | Listed building consent required |
| EWI threshold U-value | 0.30 W/m²K |
Often yes, because render is rarely 'similar in appearance' to brick, and always in a conservation area.
Not with cement. Lime allows the wall to dry; cement seals moisture in.
On a solid-wall house it is the most effective fabric measure, but it changes the elevation and usually needs consent.
Pick a slot that suits you. No obligation and no sales pressure, just straight answers on your planning route.
