Wall insulation in Owermoigne, in or out

Establishing the wall. Reveal depth and brick bond give the first opinion, the borescope gives the fact. Cavity or not, how wide, clean or bridged with mortar, dry or a wet cavity, empty or already filled and slumped. Where there is a sound cavity the whole discussion stops there, because a fill beats either alternative.

Cavity fill. Bonded bead for a narrow, obstructed or weather facing brick and block wall; blown mineral wool for a wide, clean, sheltered one. Drilled from outside on a grid, blown in, holes pointed to match. One day, the shortest payback of anything here, with Part L setting what the finished wall should reach.

External wall insulation. Board bonded and mechanically fixed to the outside, a mesh reinforced basecoat over it, then a silicone topcoat or a render carrier with a traditional finish. It gives the best U value, keeps your room sizes, keeps the masonry warm and dry, and it is the only one of the two that deals with the thermal bridge at the eaves and at the joist ends. It also takes the sills, the pipework, the meter boxes and the verges with it, and it needs a scaffold.

Internal wall insulation. Insulated plasterboard or PIR such as Celotex or Kingspan on a batten or stud frame with taped joints and a continuous vapour control layer, or wood fibre and lime where the wall is old and must stay breathable so the dew point lands somewhere that can dry. Cheaper, done room by room, and no scaffold, but it costs you 60 to 100mm a wall and it leaves the joist ends and the eaves cold unless they are detailed.

How we would actually choose. If the outside finish is already render and the eaves overhang is generous, external is usually the better building answer. If the house is faced in good brick or flint that would be a shame to bury, if the overhang is tight, or if you only want two cold rooms sorted, internal wins. We say which we would do and why, in writing.

Reveals and junctions. Whichever route, the reveals, the threshold, the floor junction, the eaves and the joist ends are where the cold bridges and the black mould live. Shallow reveals take an aerogel laminate. On an external system the reveals are wrapped in a thinner board so the window is not swallowed.

Ventilation. Trickle vents, extract fans that shift air and air bricks kept clear, to the rates in Approved Document F. Airtightness without ventilation trades a cold house for a damp one.

Failures. Fill that has slumped and left a cold band under the eaves, a wet cavity, render that is cracking and drumming, a lining fitted with no vapour control layer and now black behind. It comes out, the wall is dried, and you get a straight view on doing it again.

Same team from first visit to last, one person to ring, and no sub-contracting your work out to somebody you have never met. The quote is itemised, not a figure on the back of a card: the survey and any borescope check, the system and its thickness, making good around windows and doors, ventilation works, and disposal on separate lines, so you can compare it properly against anyone else's.

Nothing is left open or unusable overnight. The site is swept at the end of each day rather than the end of the job, and what comes out leaves with us. If something turns up once we start that nobody could have seen, you get a photograph and a price before we carry on.

There is no conservation area over Owermoigne, so external wall insulation on an ordinary house is not blocked in the way it is in the villages either side; it is still worth checking against the rules on external walls. The parish does contain listed buildings, and there consent covers internal work as well as external under section 7 of the 1990 Act; Dorset Council holds the designation records. Regulation 23 brings building control in once more than half a wall is renovated.

Ring rather than use the form. Damp patches or black mould appearing on an outside wall after cavity fill or internal lining usually means water is tracking across the cavity, or warm air is reaching a cold surface at a junction. We look before we take anything out, because the fix depends on which of those it is. Send a photograph of the outside wall as well as the damp patch, because on this kind of job the cause is usually visible from the pavement. The phone is answered 24 hours for emergencies; scheduled work runs Monday to Friday, 8am to 6pm.

Call now: 07435 839745

Nearly every village on this side of Dorset has a conservation area over its centre, and inside one of those the outside of your wall is not simply yours to change. Owermoigne does not have one, and that is genuinely useful to know before you get quotes. External wall insulation on an ordinary house here is a normal building job rather than a planning fight, and it is the better technical answer more often than people realise.

The reason is what it does at the edges. An internal lining warms the face of the wall but leaves the joist ends, the eaves and the party wall on the cold side of the insulation, so those become the strips where condensation collects. An external system wraps the whole thing, keeps the masonry warm and dry, and leaves the rooms the size they were. The cost is that it changes how the house looks and it needs a scaffold, so it makes most sense where the wall is already rendered.

There are exceptions and they matter. There are listed buildings in the parish, and on those consent is needed for work inside as well as out, so the easy answer stops applying. And on a house with good facing brick or flint, burying it under render is a decision you cannot undo, whatever the U value says. We will tell you which category you are in on the first visit.

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