Wall insulation in Sandleheath

The cavity half takes a fill. Bonded polystyrene bead is blown through a drilled pattern, or blown mineral wool where the wall is sheltered and the outer leaf is sound. The cavity has to be clear, dry and wide enough, and a wet cavity or a fill that has already failed and slumped is dealt with rather than topped up. Holes made good in a matched mortar, normally a day.

The solid half. A nine inch brick wall or a rendered rubble one in Sandleheath has nothing in it to inject. It is internal wall insulation or external wall insulation. Inside, that means wood fibre in lime on an old soft wall so it stays breathable and vapour can pass, or insulated plasterboard, PIR, Celotex or Kingspan on battens or a timber stud where the wall is dry and hard enough for a sealed face.

The junction between the two. Where the extension meets the original wall there is usually a return of solid masonry standing proud into the cavity, a straight joint, or an old external corner now sitting inside the house. Each is a cold bridge, and unless the lining is returned past it the fill in the new wall simply makes the contrast worse.

External wall insulation. Board, a render carrier and mesh, then a through coloured finish. On a Sandleheath house that is part old and part new it also does something useful visually, because it takes two different brickwork faces and makes them one. It keeps the masonry warm, so interstitial condensation has nowhere to form.

The other junctions. Reveals, the threshold, the floor junction, the eaves, the joist ends and any party wall. A shallow reveal takes a thin aerogel board. Any of them missed is a thermal bridge, and that is where the dew point lands and black mould shows up.

Failed fill. Where an earlier fill has slumped down the cavity, or wetted up because the outer leaf is cracking or has blown render, it is extracted through drilled holes and the wall dried before anything replaces it.

Ventilation. Trickle vents, a working extract in the kitchen and bathroom, and air bricks kept clear, which is what Approved Document F expects. Older houses that have been extended are often tight in the new part and draughty in the old one, and both halves need thinking about.

Thomas works out what your walls are before pricing. An older Sandleheath house that has been extended can have a solid wall at the front and a cavity-walled extension at the back, and the two need different treatment. One small hole and a borescope tell us if there is a cavity and if anything is in it.

Your quote then prices the survey, the insulation system and its thickness, making good at the reveals, any extra ventilation and taking waste away, line by line. The cavity half, if it is filled, needs a registered installer and a CIGA certificate.

Cavity fill goes in through small holes drilled in the mortar joints outside, which are then filled to match. Internal lining happens one room at a time: the room is emptied, the floor covered, and dust kept behind sheeting. Nothing is left open at the end of a day. If opening a wall shows damp, rot or old wiring, a photo and a cost come to you before anything else happens.

New Forest District Council is the planning authority. Lining a wall inside is not development, which the Planning Portal confirms, while external wall insulation changes the outer face, and the external walls guidance is the place to start on that. There are two listed entries in Sandleheath and no conservation area, so most addresses are straightforward. Building control comes in under regulation 23 once a thermal element is renovated, and Part L sets the U-value the finished wall must reach.

Phone rather than using the form if patches of damp or black mould have turned up on an outside wall since it was filled or lined. Usually the cause is rain crossing the cavity through the fill, or warm room air meeting a cold spot at a junction.

Keep the room ventilated, move furniture back from the wall, and tell us roughly how old any extension is, since the join between old and new wall is a likely cold spot. Nothing is pulled out until we know which it is, because the fix is different. Booked jobs are Monday to Friday, 8am to 6pm. Should the call go unanswered, a call back follows as soon as we can manage.

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Sandleheath has older homes built before the cavity wall existed as well as newer ones, and where an older house has picked up an extension along the way, it can end up with two entirely different wall types beneath one roof.

The seam between them is where the trouble sits. The old external corner is now an internal one, with cold masonry wrapping round it. The new cavity often dies into a solid return rather than being closed cleanly. Sometimes there is a straight joint with nothing but mortar in it. All of that carries heat out of the building in a line, and once the newer part is filled and warm, the difference across that line gets sharper rather than softer. It is why the mould in these houses appears in one corner of one room, usually where the two builds meet.

Treating it properly means the work does not stop at the change of wall type. The fill goes in the cavity, the lining goes on the solid part, and the lining is returned past the junction far enough to break the bridge. It costs a little more than doing one half, and it is the difference between a warm house and a warm house with one cold corner in it. Heat loss through a wall like this is a real number and the payback is genuine, but only if the seam is dealt with.

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

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