Rendering in Corfe Castle

Sounding the elevation. Nothing gets priced until it has been tapped. Sound render answers dead and blown render drums, and the drumming almost always runs further than the crack that made you ring. We chalk the hollow areas and the chalk decides the scope.

Hacking off. Where a render has parted from the background it is hacked off back to the stone or block, and on stone that is careful hand work rather than a breaker, because the face has to survive it. Then the wall is cleaned down, anything friable is stabilised, and it is left to dry.

Lime render on solid walls. A period pre-1919 wall here is solid limestone with no cavity, and it wants a breathable lime render: a scratch coat keyed and left, a straightening coat, then a fine float finish, each firming up in its own time. Slower than anything modern, and the only thing that will not leave moisture trapped in the wall.

Silicone thin coat. On blockwork, a polymer basecoat with a full mesh embedded in it, a primer, then a through-coloured silicone topcoat scraped to a texture. It moves with the wall and there is nothing to repaint.

Monocouche. One through-coloured material in two passes, scraped back the next day. It gives a crisp, even face but wants a good background, so it is a poor choice on a much-patched wall.

Sand and cement, pebbledash and Tyrolean. Traditional render in a scratch and float, dashed aggregate thrown into a wet coat, or Tyrolean flicked from a machine. All three are repairable, and matched off a sample panel first.

Beads, bellcast and stop ends. The render is judged at its edges. A bellcast throws water clear at the foot of a wall, stop beads finish it at a soffit or a corner, angle beads keep the reveals straight, and a movement bead lets a long elevation move without splitting.

Cracking, delamination and staining. Map crazing is a surface fault. A crack from a window head is movement, and rendering over it hides it until the next winter opens it again. Frost turns a small crack into a blown panel. Algae on a shaded wall is treated and cleaned down, not blasted.

Render over external wall insulation. With EWI the render is the weather face of the system rather than a finish, going onto a render carrier board or the boards themselves with a mesh basecoat and a thin coat over it. Every bead, sill and pipe is reset to the new thickness. In this village it belongs on the newer houses, not on the stone.

No rate per square metre, because the square metres are the easy part; what is already on the wall decides the price.

Getting to it. A cottage on East Street with no room to stand a tower, a bungalow gable off the main road and a two storey rear elevation are three different platforms. A bungalow gable comes off a tower, a three storey elevation wants a scaffold, and the platform has to stand for the whole system rather than a day. The work at height rules are why it is a priced line rather than something folded into a rate.

What is already on the wall. Rendering over sound brick is one job. Hacking off blown sand and cement, or a pebbledash that has parted from the background, is another, and it is the part nobody can see from the road. We tap the whole elevation before quoting, because the hollow areas set the hours.

The system, and what the wall behind it needs. Silicone thin coat over insulation, monocouche through-coloured, or traditional sand and cement all price differently and behave differently. On a solid wall that has to breathe, a plastic-rich modern system traps moisture and moves the problem inside, so the right system is a wall decision rather than a colour decision.

Comparing quotes? Ask which system is being quoted and how many coats, whether the old render is being hacked off or overlaid, whether beads, bellcast and stop ends are included, whether the scaffold is in the price, and what happens to the existing sills and pipework. Two quotes for the same job are usually two different jobs.

Corfe sits in the one real break in the Purbeck ridge, and the wet weather here arrives from the south west. A gap in a ridge does to wind what a doorway does to a draught: it speeds it up and it concentrates it. So west and south west facing walls here take far more driven rain than the same wall would a couple of miles either side, and that is the wall that fails first. BS 8104 is the code that puts a number on exactly that, and it is the reason a render specification is a weather decision rather than a colour decision.

What it changes in practice is the detailing rather than the material. On an exposed elevation the mesh runs the full wall rather than only at the openings, every window and door corner gets a diagonal reinforcing patch because that is where a crack starts, the sills need a throat and an end stop so water leaves the wall instead of running back under, and the render stops on a bellcast rather than dying onto the plinth. Get those right and an exposed wall lasts as long as a sheltered one.

We cover Corfe Castle, Kingston, Church Knowle, Harmans Cross and Stoborough, broadly BH20, under Dorset Council. You are dealing with Bournemouth Roofing & Building, the trading name of Bournemouth Roofing & Building Ltd, registered in England and Wales, company number 15471719, which you can look up in a minute. Thomas Hannen's business, and he is the one who comes out to price the job, not a salesman. A verified customer's 10 out of 10 on Checkatrade. The visit and the written quote are both free.