external
Rendering, external walls
Rendering costs £45 to £75 per square metre including scaffold, so a typical semi-detached house runs £4,000 to £9,000 depending on how much of it is being done. Scaffold is a fixed cost of £700 to £1,400 whatever the area, which is why one elevation rarely costs a quarter of four.
What this covers
What it costs. Rendering costs £45 to £75 per square metre including scaffold, and £60 to £95 for a silicone or monocouche system. Full cost breakdown.
What the job covers
- Rendering a solid wall or blockwork extension in sand and cement
- Hacking off blown render and making good the substrate
- Fitting bellcast, stop and angle beads before the scratch coat
- Rendering over an existing sound render with a thin-coat system
- Rendering a gable or a chimney stack off scaffold
What is involved
External render is a different trade from anything done indoors, and a plasterer who skims beautifully may not touch it. It is worked off scaffold in weather that has to be right, in a material that has to move with the wall rather than against it, and a failure shows up as blown patches and staining two winters later rather than as a bad finish on the day.
A traditional sand and cement render goes on in two or three coats over a scratch coat, with beads at every corner, sill and stop. A modern thin-coat system is a polymer basecoat with a mesh embedded in it and a coloured topcoat over, and the colour is through the material rather than painted on, so it does not need redecorating. Which one suits depends on the wall underneath more than on preference.
The question that decides most jobs is what is already there. Rendering over sound existing render is a fraction of the cost of hacking it all off; rendering over a wall that is holding damp seals the damp in. On anything solid-walled and pre-1919 that is a lime question, not a cement one.
Rendering a solid wall or blockwork extension in sand and cement, one of the jobs a rendering specialist is hired for.
Choosing someone for the job
Ask which system they are quoting and why that one suits this wall. Ask whether scaffold is included and for how long. Ask what happens to the existing render, because hacking off is a separate cost and a separate skip. If the house is solid-walled and pre-1919, ask specifically about breathability before anything cement-based goes near it.
Common questions
Do I need planning permission to render my house?
Usually not: rendering is normally permitted development. It is not if the house is listed, in a conservation area, in a national park or an area of outstanding natural beauty, or if a condition on the original permission says otherwise. Check with the council before, not after.
How long does render last?
Sand and cement, twenty to thirty years if it was right when it went on. Silicone and monocouche systems are generally quoted at twenty to twenty-five and do not need repainting, which is most of their argument.