Wall insulation in Thorney Hill

Measuring the reveals. On an old cottage with the original frames set well back, there may be 100mm of masonry to insulate into. On a house with replacement windows fitted forward in the opening there can be under 40mm. That measurement decides the material, and it is taken before anything else is specified.

Thin boards and aerogel. Where there is depth, a thin PIR laminate does the reveal well enough. Where there is barely any, aerogel board gets a usable improvement into 10 or 15mm, which is the difference between reworking the window and working around it. It is the expensive material on the job and the smallest quantity of it.

Internal wall insulation, IWI, on a solid wall. Insulated plasterboard bonded to the masonry, or a batten and stud frame filled with mineral wool. On old solid brick we lean towards a breathable build up, wood fibre and a lime skim, rather than a foil faced PIR, because a vapour tight board pushes the dew point back into the wall. Any vapour control layer is taped and sealed per BS 8000-8.

Cavity fill where there is a cavity. On the post-war houses in Thorney Hill, a clear, dry gap of a usable width is drilled on a pattern, filled and made good in a day. Bonded polystyrene bead suits the exposed elevations, which out here face south west; blown mineral wool is fine in a clean, sheltered cavity.

External wall insulation, EWI. Boards, a render carrier and a render finish. It keeps the room size and the reveals become an external detail instead of an internal one. On a cottage in open country it changes the appearance completely, which in this landscape is the first thing to settle rather than the last.

The rest of the junctions. The threshold, the floor junction, the eaves and the joist ends. A cold bridge, or thermal bridge, left at any of them collects condensation whatever the u value of the wall beside it, and on a solid wall the joist ends are the ones that quietly rot. Where the cavity is continuous a party wall gets a barrier.

Ventilation and draughts. Lining an old cottage tightens it considerably and the moisture from cooking, washing and breathing has to go somewhere. Trickle vents, a working extract fan and clear air bricks are part of the work, and Approved Document F sets what is expected. Sealing draughts alongside is what turns a better u value into a room that feels different.

The wall area is the easy part. The junctions, the exposure and what is in the cavity decide the price.

What sort of wall. Post-war walls in Thorney Hill usually have a cavity, and if the borescope shows it empty and dry, filling it is quick work from outside. The older cottages have solid brick, which can only be lined on the inside or wrapped on the outside, and that is far more work.

Exposure. The south west walls in Thorney Hill face open ground, and driven rain can cross a filled cavity on a very exposed wall. The fill is chosen against the wind-driven rain code, and pointing and render are checked first.

Movement. Clay that shrinks and swells can crack a wall, and a crack lets water into the cavity, so it is repaired before any fill goes in.

Round the openings. Window and door reveals, the floor edge, the eaves and any party wall are where cold bridges form and where mould shows if the detail is skimped. Doing them properly is slow, and it is often what separates two quotes.

Access. Work at height rules apply to drilling from outside too, even at bungalow height.

Ask anyone else whether the cavity has actually been looked into with a borescope, which fill or board is specified and how thick, and how the reveals will be finished.

Thorney Hill lies 6.8 miles from our Boscombe base. We insulate walls across Thorney Hill and Holmsley, over to Bransgore and along the lanes to Burley, broadly BH23. Cavity fill and lining here are signed off through New Forest District Council building control.

Bournemouth Roofing & Building Ltd, registered in England and Wales, company number 15471719, is run by its owner Thomas Hannen, who checks the wall and prices it himself. A verified Checkatrade review from a customer gives us 10 out of 10. The visit and the written itemised quote are free. Before you book a visit in Thorney Hill, you can read our customers' Google reviews, word for word, on our reviews page.

Most repairs in Thorney Hill 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.