Wall insulation in Thorney Hill, where the reveals decide it
Line the flat of the wall and leave the reveals bare and you have built a cold frame around every window, which is where the mould turns up.
The site visit is free and so is the written itemised quote. Thomas Hannen prices every job himself.
Over a fifth of the houses around Thorney Hill predate 1919, and in a cottage of that age the window reveals are the part of the job that decides whether it worked. Line the flat of the wall, leave the reveals as they are, and you have left a cold frame around every opening. That is exactly where the condensation lands, so on these houses the reveals are not a detail, they are the job.
The calls follow from that. Black mould in the corners of a window, on the plaster beside the frame rather than out in the middle of the wall. A cold front room in an old cottage. Or a newer house on the lane where a filled cavity has started showing damp on one elevation.
We look at the wall and the openings together. One small hole and a borescope shows whether there is a cavity and what is in it. Then we measure every reveal, because how much depth there is between the frame and the face of the wall sets what can be used. The site visit and the written itemised quote are both free.
The work
Cottage walls, deep sills and shallow reveals
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 here, 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.
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.
Thorney Hill sits inside the New Forest National Park, so the National Park Authority is the planning authority and design is scrutinised on anything visible; the National Park property map shows what covers your address. Internal lining and cavity fill are building control matters, while an external render system is a planning question here. Where an existing wall is upgraded, regulation 23 sets what it has to reach under Part L.
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. A brick cottage with small deep set windows, a post-war house on the lane and a detached property in open ground are three different jobs before a hole 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. We are about nine miles away through Bransgore, so an address around Thorney Hill is normally looked at within a couple of days. The phone is answered 24 hours for emergencies; scheduled work runs Monday to Friday, 8am to 6pm.
Worth knowing
The reveal is where an insulated wall usually fails
Picture a room with 60mm of insulated board on the wall and nothing on the reveals. The wall surface is now warm, so the air in the room holds more moisture without anything visible happening. The reveal is still bare masonry, colder than it was relative to everything around it, and it is where that moisture finds a cold surface. Within a winter there is mould down the sides of the window and the owner concludes that insulating the wall caused it. In a sense it did.
Doing it properly means carrying the insulation into the reveal, over the head of the opening and onto the sill wherever there is room, then sealing the joint between the board and the frame. Where the frame sits too far forward for even a thin board, aerogel goes in instead, or the window is reset while the room is open. It is fiddly, slow work and it is a real part of the labour on a cottage with a lot of small openings. It is also the first thing a cheap quote leaves out, so it is the first thing to ask about.
Who you are dealing with
A local firm you can check
We cover Thorney Hill, Bransgore, Holmsley and the lanes towards Burley, broadly BH23, under the New Forest National Park Authority. 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
Thorney Hill questions we get asked
Why does mould show beside a window and not on the open wall?
Because the reveal is the coldest surface in the room, especially if the wall beside it has already been insulated. Warm the reveal and seal the joint to the frame and it goes.
What if there is no depth at all in the reveal?
Then aerogel, which gets a useful improvement into 10 or 15mm, or resetting the window while the room is open. Leaving the reveal bare is the one option we would talk you out of.
Does the National Park affect what I can do?
It affects the outside. An external render system is a planning question here because appearance is scrutinised, while lining inside and filling a cavity are not.
Does a cottage with lots of small windows take longer?
Yes, noticeably. How long a room runs depends on the openings, because each reveal, head and sill is worked separately. It is slower than a cavity fill and we price it honestly.
Should I use foil faced board in an old cottage?
Usually not on solid brick. A vapour tight board moves the dew point into the masonry, so a breathable build up that lets the wall dry inwards is the safer choice.
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Have the reveals measured before the boards are chosen
Thomas comes out, reads the wall, measures every opening and prices the lining and the reveals in writing. The visit and the quote are free.