Wall insulation in Sandleheath
A fifth of the homes here predate the cavity and a quarter were built since the eighties, so a great many houses are both at once.
The site visit is free and so is the written itemised quote. Thomas Hannen prices every job himself.
A lot of houses here are two buildings joined together: an older solid walled part and a newer extension built in brick and block with a cavity. Those two walls need completely different treatment, and the place where they meet is almost always the coldest line in the house.
So the calls tend to be about one room rather than a whole property. The back of the house that will not warm up. Mould in the corner where the extension joins the original wall. A quote to fill the cavity that says nothing about the half of the house that has not got one.
We walk round the outside first and work out where the original building stops. Then one drilled hole and a borescope in the newer part, and on the older walls the thickness, the plaster, the render or the pointing, and where the joists bed in. Then a written itemised quote with the survey, the system, the junctions and the ventilation on separate lines. The visit and the quote are free.
What gets done
Two kinds of wall on one house
The cavity half. Bonded polystyrene bead 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 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 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.
How it runs
From your call to a written price
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.
New Forest District Council is the planning authority. Insulating the inside of a wall is not development and needs no permission, which the Planning Portal confirms, while external wall insulation changes the outer face and the external walls guidance is where to start on that. There are 2 listed entries in the parish and no conservation area over the village, so most addresses here 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 has to reach.
Cost
What decides the price of a wall insulation job
No rate per square metre, because the wall area is the easy part; what happens at every window, door and floor junction is not.
Getting to it. An older cottage with a modern rear extension, a post war semi and a nineties detached house with a wide clear cavity are three different jobs before anything is drilled. Cavity fill is drilled from outside and a bungalow comes off a tower where a three storey gable wants a scaffold. Internal lining is worked room by room from inside, so it is your rooms rather than a platform that gets disrupted. The work at height rules still set the platform.
Which wall you actually have. A cavity that is clear and dry can be filled in a day. A solid wall cannot be filled at all, and has to be lined inside or insulated outside, which is a different job at a different price. A borescope through one drilled hole settles it, and no honest quote is written before that.
The junctions, not the field of the wall. Reveals at windows and doors, the floor junction, the eaves and any party wall are where heat escapes and where condensation shows up if the detailing is wrong. That work is slow, it is most of the labour, and it is the first thing a cheap quote leaves out.
Comparing quotes? Ask whether the wall has actually been checked with a borescope or just assumed, what system and what thickness is specified, how the reveals and floor junction are being detailed, whether ventilation is being addressed, and who makes good the plaster and decoration afterwards. Two quotes for the same job are usually two different jobs.
If damp has appeared
Damp or mould after a wall was insulated
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. Tell us roughly when the extension went on, because the age of that wall usually explains where the cold line is running. The phone is answered 24 hours for emergencies; scheduled work runs Monday to Friday, 8am to 6pm.
Worth knowing
The seam between the old house and the new one
Around a fifth of the homes here were built before the cavity wall existed and roughly a quarter went up from the eighties onwards, and a good many of the older ones have picked up an extension somewhere along the way. That leaves houses with two entirely different wall types under 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.
Who you are dealing with
A local firm you can check
We cover Sandleheath, Alderholt, Damerham and the lanes into Fordingbridge, broadly SP6, under New Forest District Council. You are dealing with Bournemouth Roofing & Building, the trading name of Bournemouth Roofing & Building Ltd, registered in England and Wales, company number 15471719, which you can look up in a minute. Thomas Hannen's business, and he is the one who comes out to price the job, not a salesman. A verified customer's 10 out of 10 on Checkatrade. The visit and the written quote are both free.
Questions
Sandleheath questions we get asked
Half my house has a cavity and half does not. Can both be done?
Yes, and they are priced as separate lines because they are separate jobs. What matters is that the work carries on past the point where one wall type becomes the other.
Why is the cold corner always where the extension joins?
Because the old external corner is still there inside the wall, carrying heat out in a line. Filling the new cavity alone makes the contrast sharper rather than fixing it.
How do you tell where the original house ended?
From outside, mostly: a change of brick, a straight joint, a different roof line or a step in the wall. The borescope confirms where the cavity actually starts.
Would external insulation tidy up the mismatched brickwork?
It would, because everything ends up under one render finish. It is worth weighing against the cost and the change to how the house looks.
Can it be done a bit at a time?
No. Most people start with the coldest part, and the itemised quote lets you see what each elevation would cost before deciding.
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Get both halves of the house priced properly
Thomas comes out, works out where the old wall stops and the cavity starts, and prices both in writing. The visit and the quote are free.