Wall insulation in Blandford Forum
Solid brick in the middle of town and cavity walls around the edge, so the first job is finding out which of the two you actually own.
The site visit is free and so is the written itemised quote. Thomas Hannen prices every job himself.
Blandford is two towns as far as a wall is concerned. The Georgian brick centre has solid walls with nothing inside them to fill, so the routes are lining the inside or insulating the outside, and outside is a planning matter here. The estates around the edge are brick and block with a cavity, and there the first job is finding out what is already in it.
People ring for three reasons. A front room in one of the town houses that never gets warm however long the heating runs. Black mould in the corner of a bedroom on an outside wall. Or a house filled years ago under a scheme nobody kept the paperwork for, where damp now shows inside after driving rain.
We look at the wall itself before naming a system: thickness at a reveal, the bond in the brickwork, and a borescope through one small hole where there is a cavity. The site visit is free and so is the written itemised quote, and where the honest answer is that your wall is better left alone, that is what it will say.
The work
Solid brick in the middle, cavities on the edge
Finding out which wall you have. A nine inch solid brick wall and a brick and block cavity wall look the same from the pavement. The tells are the thickness at a window reveal and the bond, and where those are not conclusive we drill one hole in a mortar joint and put a borescope through. That gives the cavity width, whether it is clear and dry, and whether anything has been injected already.
Cavity fill, where the cavity earns it. A clear, dry cavity of decent width is filled from outside through a pattern of drilled holes, with bonded bead or blown mineral wool, and the holes made good in matched mortar. We do not offer a guarantee scheme of our own; a fill is normally installed under an independent one, so ask whoever drills your wall which scheme covers it.
A fill that has failed. Old material settles. A slumped fill leaves the top of the wall empty and a packed, damp mass at the bottom, which is worse than an empty cavity because it carries water to the inner leaf. The symptom is black mould inside after a wet, windy spell. Extraction comes out through the lowest course before anything new goes in.
Internal wall insulation. On a solid wall this is the practical route and in the town centre usually the only one. Insulated plasterboard on a continuous adhesive bed, or PIR such as Celotex or Kingspan between battens or a stud, taped and skimmed to BS 8000-8. Coldest rooms first. It takes floor width, so reveals, skirtings, sockets and radiators move with it.
External wall insulation. Boards fixed and rendered over a render carrier. It is the best U value you will get on a solid wall, because it wraps the building, leaves your rooms alone and cures the cold bridge at every floor junction at once. It also changes the look of the house, which is why here it is a planning question before a heat loss one.
The junctions, which are the actual job. Reveals, the threshold, the floor junction, the eaves and the party wall are where a lining either works or leaves a thermal bridge worse than the one it cured. Reveals take a thin board, or aerogel where there is no room. Joist ends in a solid wall need air kept round them, or they rot quietly.
Moisture and air. Insulating a wall moves the dew point and cuts the air changes, so vapour control and ventilation belong in the same quote: trickle vents, a working extract fan in the kitchen and bathroom, air bricks left clear. BS 5250 covers moisture and Approved Document F the ventilation. Seal the draughts first; the payback is immediate.
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.
Dorset Council is the planning authority. Lining a wall inside is not development, which is why Planning Portal sets out where insulation needs permission treats it differently from cladding. External insulation alters the outside of the building, and inside the Blandford St Mary and Bryanston Conservation Area appearance is controlled, so it needs an application. On the two hundred or so listed entries around the town, even internal lining can need listed building consent. And regulation 23 means renovating more than half of a wall brings the whole of it up to Approved Document 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 Georgian town house fronting straight onto the street, a post-war semi with a side path and a bungalow on the edge of town are three different jobs. 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. Blandford is about sixteen miles up the valley from us, so a damp wall here is normally seen within a day or two and you get a photograph of what we find. The phone is answered 24 hours for emergencies; scheduled work runs Monday to Friday, 8am to 6pm.
Worth knowing
Why the outside of a Georgian wall is not your decision
The centre of Blandford was rebuilt in brick after the fire, and the old streets read as one piece rather than as separate houses. That is why the conservation area exists, and why external wall insulation on a frontage here is not a realistic proposal. It pushes the wall forward, buries the reveals and breaks the line of the terrace. Planning Portal guidance on external walls explains where cladding needs permission, and in a conservation area assume it does.
So on a solid walled house in the middle of town the honest options are a lining inside, or nothing. Lining is worth doing on the rooms you live in, but only detailed properly: reveals returned, the floor junction dealt with, joist ends left able to breathe, and a build up that suits an old wall rather than sealing it. Done badly it puts a cold, damp surface behind a warm board, and the EPC improves while the room does not.
The estates built from the sixties onwards are a different proposition. Those walls have a cavity, sit outside the conservation area, and a fill or external insulation on a rear elevation is straightforward there.
Who you are dealing with
A local firm you can check
We cover Blandford Forum, Blandford St Mary, Bryanston and the villages along the Stour, broadly DT11, under Dorset 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
Blandford Forum questions we get asked
How can I tell whether my Blandford house has a cavity?
Measure the wall thickness at a window reveal and look at the brick bond. A solid nine inch wall shows headers laid across it; a cavity wall shows stretchers throughout. Where that is not clear we drill one hole and look with a borescope.
Can I put external insulation on a house in the conservation area?
On a frontage, realistically no. It changes the appearance of the building and the street, so it needs an application. A rear elevation on a later house is a different conversation.
Will lining the inside make my rooms noticeably smaller?
Yes, and you should know before you start. Sockets, radiators and skirtings move with it, which is why it is normally done to the coldest rooms rather than the whole house.
Damp appeared after our wall was filled. What causes that?
Usually the fill has slumped or bridged, so water crossing the outer leaf now has a path to the inner one. Sometimes the wall was too exposed to fill at all. We look before taking anything out.
Is a warmer wall going to give us more condensation?
It can, if nothing else changes. A tighter house needs somewhere for moisture to go, so trickle vents, working extract fans and clear air bricks are part of the work.
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Find out what your wall is before you insulate it
Thomas comes out, checks the wall thickness and puts a borescope through where there is a cavity, then prices it in writing. The visit and the quote are free.