Rendering in Tarrant Monkton, cob and flint walls

Tapping and reading the wall come first. On a Tarrant Monkton house, a hammer handle tells you where the render has blown. The wall thickness at a window reveal tells you what it is. Anything much over 450mm with soft edges is likely cob, and cob is the one background where the wrong render does structural harm rather than cosmetic harm.

Taking cement off. On old cottages in Tarrant Monkton the usual culprit is a hard cement render applied decades ago. It cracks, water gets behind it, and because the cement will not let that water back out the wall behind stays wet. On cob that means the earth softens; on flint and brick it means frost damage and salts. Removing it is careful hand work, not a breaker.

Lime render. Applied in coats onto a dampened background: a hair reinforced scratch coat left with a good key, a float coat ruled out, and a finish coat or a limewash over it. Soft, breathable and slightly flexible, so it takes the movement instead of passing it to the wall. Kept damp and protected while it carbonates, which is why the scaffold stays sheeted.

Flint and brick repair before rendering. There is no point rendering onto loose material. Open joints get raked and repointed in a lime mortar first, and anything spalled is cut out, so the background is sound before a coat goes on.

Sand and cement, pebbledash and Tyrolean. Ordinary and correct on the twentieth century houses in Tarrant Monkton. Scratch coat, float coat, and dash or Tyrolean where the elevation already carries it, matched by sample panel where the aggregate can still be had.

Silicone thin coat and monocouche. Both good systems on a modern Tarrant Monkton cavity wall: a stabilising primer where the background is dusty, a mesh reinforced basecoat, then a through coloured topcoat that needs no painting. Neither belongs on cob or on a solid period wall, and we will say so rather than take the order.

Beads, bellcast and stop ends. On modern work a bellcast bead throws water clear at the base, stop beads finish reveals and angle beads keep corners true. On cob we form the arris and the drip by hand, because a hard metal bead in a soft wall gives the render something to crack against.

External wall insulation. On a modern Tarrant Monkton house, board fixed outside and rendered over, on a render carrier where needed, lifts the thermal performance without losing a room. On a breathable solid wall it takes a specialist build up, and on a protected frontage it usually is not the answer at all.

Cracks, delamination and algae. A straight hairline crack is shrinkage. A stepped or widening crack is movement behind the render. Green on a shaded elevation lifts with a gentle clean down and a treatment, never a pressure washer on lime.

What is on the wall now. Putting render on sound brick is a straightforward job. Where old cement render or dash has come away from the wall behind, all of it must be knocked off first, and you cannot tell how much until someone taps it over.

What the wall is built of. Cob, flint and soft old brick need to dry out through their surface. Lime render lets them. A hard cement render, a through coloured monocouche or a silicone thin coat seals the face and pushes the damp inside. Lime takes more coats and more drying time, and it costs more in labour.

Access. A Tarrant Monkton cottage tight to the lane needs a scaffold kept clear of the eaves, more so if the roof is thatched. A barn gable needs one reaching the apex. The work at height rules make the platform a priced line.

Details. A bellcast bead over the damp course, stop beads at openings, and taking off and refitting pipework and sills all take time.

Ask any other firm which render they propose and in how many coats, whether they are stripping the old finish or going over it, and whether beads, sills and pipework are in the figure.

A cob wall is chalk, earth, straw and water, built thick, standing on a stone or brick plinth and traditionally kept dry by a good hat and good boots: a generous roof overhang above and a plinth below. It is not waterproof and was never meant to be. Rain wets the outer face, and the wall dries back out through that same face when the weather turns. Everything about how it survives depends on that drying.

A cement render stops it. Water still gets in, through a crack, around a window, up from a raised path, but it can no longer get out, so it sits in the earth and softens it. By the time the render is bulging the damage is already done, and it is a rebuild rather than a repair. The historic building guidance on cement and traditional masonry is blunt about it. So if your cottage has a hard grey render that rings dead when you tap it, get it looked at while it is only a render problem.

We are about fifteen miles from the Tarrant valley, based in Boscombe, and we cover Tarrant Monkton, Tarrant Keyneston, Tarrant Hinton and the lanes towards Blandford, broadly DT11. Dorset Council is the authority here. You are dealing with Bournemouth Roofing & Building Ltd, registered in England and Wales as company number 15471719. Before you book a visit in Tarrant Monkton, you can read our customers' Google reviews, word for word, on our reviews page.

The business is Thomas Hannen's, and he taps the walls and prices the rendering himself. We hold a verified customer's 10 out of 10 on Checkatrade. The site visit is free, as is the written quote setting out each coat and bead.

Most repairs in Tarrant Monkton need no application at all. What decides whether a change to the outside of your house does is who the council is, whether a conservation area or a listing applies, and whether the place sits in a protected landscape.