What render is for
Render is a coat of material over the outside of a wall that keeps rain off the masonry and gives the house a finished face. On a modern cavity wall it is mostly cosmetic and protective. On a solid brick or stone wall, and most of the housing in Leeds, Bradford and the towns between is solid-walled, it is the thing standing between the weather and the plaster inside. A render that cracks or holds water is worse than no render at all, because it keeps the wall wet.
That is why the choice of system matters more than the colour. The right render for a gable depends on what the wall is made of, which way it faces, whether it moves, whether it needs to breathe, and how much maintenance you are willing to do.
Sand and cement
The traditional modern render: sand, cement and sometimes lime, mixed on site and applied in two or three coats over a scratch coat, finished smooth for painting or with a textured face. It is strong, cheap and every renderer knows it. On a well-built block wall or a modern extension it works well and lasts.
Its weakness is rigidity. Sand and cement does not flex, so on an older house that moves with the seasons it cracks, and each crack lets water in behind a coat that cannot let it back out. It also has to be painted, and repainted every several years, and the paint adds another impermeable layer. On solid walls it is the render most often found failing.
- Suits: new blockwork, modern cavity walls, extensions
- Fails by: cracking, trapping water, paint peeling
- Needs: painting, and repainting every few years
Monocouche
A factory-mixed, through-coloured render applied in one thick coat, usually around fifteen millimetres in two passes, and scraped back with a nail float once it firms to give the open, sparkly texture seen on most new-build estates. The colour runs all the way through, so chips do not show grey and it never needs painting. It is durable, reasonably priced and quick on a good wall.
It is still cement-based and still fairly rigid, so it wants a sound, consistent background and proper movement joints. On a mixed or moving old wall it can crack like sand and cement does. Where it suits, it is a good value long-term finish, and it is the usual alternative quoted alongside silicone render.
- Suits: new blockwork, sound consistent walls
- Fails by: cracking on moving walls, staining on shaded elevations
- Needs: no painting; occasional cleaning
Silicone thin-coat systems
A system rather than a product: a polymer-modified base coat with alkali-resistant mesh bedded into it, a coloured primer, and a thin silicone-resin finish coat floated to a fine texture. The mesh spreads movement so cracks do not telegraph through; the silicone repels water while letting vapour out; the colour is through the finish. K Rend, Weber and others all make versions.
It costs more in materials than sand and cement or monocouche, and it depends on the base coat being done properly, which is where cheap jobs go wrong. In return it stays flexible, stays clean, does not need painting and works over old render and over insulation boards. On an older house that is being rendered for the long term it is usually the recommendation.
- Suits: older and mixed walls, over existing render, over insulation
- Fails by: skipped mesh or base coat; applied in frost or rain
- Needs: washing occasionally; nothing else
Lime render
The oldest system and the right one for the oldest walls. Lime, sand and sometimes hair, applied in two or three coats over a lime-pointed wall, finished smooth, floated or as a roughcast, and traditionally limewashed. It is soft, breathable and flexible; it lets a solid stone or brick wall get wet and dry out again, which is how those walls were designed to work. Cement on the same wall traps water and eventually takes the face of the stone off with it. The lime plastering page covers the material properly.
It is slower to apply, slower to cure, needs a renderer who knows it, and needs limewash or a breathable paint rather than masonry paint. On a Victorian stone terrace or a farmhouse it is worth all of that.
- Suits: solid stone and pre-1919 brick, listed and conservation buildings
- Fails by: being covered in impermeable paint, or applied too thick too fast
- Needs: limewash renewed periodically; breathable paints only
Pebbledash and roughcast
Pebbledash throws small stones into a wet cement top coat; roughcast mixes them into the coat. Both were the cheap, forgiving finish of the inter-war estates and both are now mostly at the end of their life. Cracked, hollow and painted several times, old dash traps water like any cement render. It can be repaired in patches, rendered over with a meshed silicone system if it is sound, or stripped and replaced. The pebbledash removal page goes through the decision.
New roughcast in a lime or a modern mix is still a legitimate finish where the whole street has it and the house should stay in step. It is the appearance people dislike, not the method.
- Suits: matching a street of inter-war houses; a lime roughcast on old stone
- Fails by: cracking, holding water, hiding poor brick
- Needs: painting if cement-based; repairs before winter
Rendering over insulation
If the gable is solid brick or stone and cold as well as tired, the render can go on over a layer of insulation. Rigid boards are fixed to the wall, base-coated and meshed, and finished with a silicone system exactly as a bare wall would be. The house ends up warmer, drier and rendered in one programme, and the scaffold and the finish are shared between the two jobs. That is external wall insulation, and on a plain solid-walled gable it is nearly always worth pricing alongside a plain re-render.
It is not right where the elevation is protected, where the stone is the point, or where the details cannot be extended. The survey tells you which.
How to read a rendering quote
A good quote names the system and the manufacturer, says whether the existing render is being repaired, overcoated or removed, lists the base coat and mesh separately from the finish, includes the scaffold, the beads and the details, and gives a realistic programme that allows for the weather. A quote that gives one number per square metre with no system named is a quote for whatever is cheapest on the day.
The house rendering page describes how we survey a wall and build a quote from it. Whichever contractor you use, ask them which system, why that one for this wall, and what it will need from you in ten years.
