Wall insulation in Cranborne

Working out what you have. A nine inch solid wall, a thicker rubble or flint wall and a brick and block cavity wall all look similar once they are rendered. A borescope through one hole tells us which, and whether a cavity is clear, dry and wide enough to take a fill at all.

Breathable internal wall insulation. On a solid Cranborne wall of any age the safe build up is vapour open: wood fibre board bedded in a lime mortar and finished in lime plaster, or a similar capillary active system. Moisture that gets into the wall can still travel and leave. There is no plastic sheet trapping it at the back of the board, which is the mistake that causes trouble later.

Where a rigid board is right, and where it is not. Insulated plasterboard, or PIR board such as Celotex or Kingspan between battens or a stud, is quick, thin for the performance and entirely correct on a modern wall or a dry, hard fired brick one. On a soft, damp or rubble filled wall it seals the inside face, and the moisture that used to evaporate into the room stays in the masonry.

The junctions. Reveals, the threshold, the floor junction and the joist ends. Timber built into an old Cranborne wall is the detail that matters most, because a lining makes the wall around those joist ends colder and wetter than it was. We keep the ends ventilated, never boxed in. Where a reveal has no depth, a thin aerogel board still goes in.

Cold bridges. A Cranborne lining that stops at a party wall, a chimney breast or a ceiling makes a thermal bridge at that line, and a thermal bridge is where the dew point lands and black mould turns up. Returns and overlaps are drawn at the survey rather than improvised on site.

Cavity fill on the newer houses. Bonded polystyrene bead, or blown mineral wool on a sheltered wall with a sound outer leaf, blown through a drilled pattern with the holes made good in a matched mortar. A house is normally a single day.

Failed fill and ventilation. An old Cranborne fill that has slumped, or wetted up through cracking render, comes out through drilled holes and the wet cavity is dried first. Then trickle vents, a working extract and air bricks kept clear, because Approved Document F expects a tighter house to still lose its moisture somewhere.

Before anything is suggested, Thomas works out what your wall is. Where a cavity is possible he drills a single small hole and looks in with a borescope. On a solid wall he checks the damp and the finish. Then he writes the price himself, and names who fits any cavity fill.

On the quote, each item has a figure: that first survey with the borescope, the chosen system and how thick it is, making good at every window and door, any ventilation works, and taking waste away.

Older houses in Cranborne are often built of solid brick or flint, with no cavity to fill. They need a breathable lining inside, such as wood fibre with a lime finish, or an external system where it suits and is allowed. Newer infill houses may have a proper cavity. We line one room, finish it, and move to the next, so the rest of the house stays usable. Offcuts and old plaster go each day. A wet or damaged wall behind the old finish is photographed and priced before we go on.

Start with the council's heritage pages before any outside system, as Dorset Council is the planning authority and the village is in the Cranborne Conservation Area. Listed status reaches inside the house as well, so internal linings on a listed building need listed building consent. For an unlisted house, lining the inside is not development, which the Planning Portal confirms. Renovating a wall as a thermal element brings building control in under regulation 23, with Part L setting the U value to reach.

If an outside wall has grown damp patches or black mould since it was filled or lined, two explanations usually cover it. Rain is being carried across the cavity by the fill, or indoor warmth is hitting a cold junction and condensing.

On an old solid wall, a lining that cannot breathe can also hold damp against the brick or flint. Note how long the patch has been there and whether it dries in summer, because that points to the source. The first visit finds the cause before anything is removed. Planned work runs Monday to Friday, 8am to 6pm. If damp is spreading, ring us, not the form, and if the phone is not picked up, we will return your call as soon as we can.

Call now: 07435 839745

A conservation area is about how the place looks. External wall insulation adds a hundred millimetres or more to every elevation, buries the sills and the eaves detail, and replaces the face of the building with render. On a village street of brick and flint that is a change of character, and it is the sort of application that is refused rather than granted.

That leaves the inside face, and it changes the engineering completely. Insulating outside keeps the masonry warm. Insulating inside makes it colder, because the heat that used to reach it no longer does. A colder wall holds more moisture and dries more slowly, and if you have also sealed the inside face with foil backed board and a vapour barrier, the water that used to evaporate into the room has nowhere left to go. That is how interstitial damp and rotten joist ends start.

So on a wall of any age here we build the lining vapour open, in wood fibre and lime rather than plastic and foil, and we manage the ventilation at the same time. It is a slower and more careful job than screwing boards to a wall. Heat loss through the walls is usually the largest line on the EPC of a house like this, so the payback is real, but it only holds if the wall stays sound.

Nearby places we also cover for wall insulation, with straight-line distances from Cranborne, and the other trades we offer in Cranborne itself.

Everything we do in Verwood Wall insulation, all areas Every area we cover