Wall insulation in Langton Matravers
Solid Purbeck stone lined from the inside in a build up that still lets the wall dry, with the reveals and floor junction detailed, across the village and BH19.
The site visit is free and so is the written itemised quote. Thomas Hannen prices every job himself.
Most of the older housing in Langton Matravers is built of Purbeck stone, and a Purbeck stone wall is solid. There is no cavity in it, so there is nothing to fill, and any firm offering to inject one is selling you a drilled wall. The honest options here are lining the inside, insulating the outside, or leaving the wall alone and spending the money elsewhere.
The calls from the village are nearly all the same shape. A room on the south west corner that never feels warm however long the heating runs. Black mould behind a wardrobe. Or a cottage where somebody has already put insulated plasterboard on one wall and the damp has moved next door.
We look at what the wall is made of, inside and out, before anyone talks about systems. Then it goes into a free written itemised quote with the survey, the build up, the reveals and the making good on separate lines.
The work
Stone walls, and the lining that suits them
Finding out which wall you have. Rubble stone, nine inch solid brick and a later brick and block cavity all sit within a few hundred yards of each other here, and plenty of houses are one at the front and another at the back. We measure the wall thickness at a reveal, look at the bond, and where a cavity is possible we drill one hole and put a borescope in. That check stops the most expensive mistake in this trade.
Internal wall insulation. On a solid stone wall this is the practical route. Either insulated plasterboard bonded and mechanically fixed back, or a stud and batten frame with mineral wool or PIR board between it. On Purbeck rubble the wall face is rarely flat, so a batten frame packed to line beats dabbing a board onto a lumpy background. It takes 60 to 100mm off the room, which is why we set it out on paper first.
Breathability, and why it matters more here. A stone wall gets wet in a south westerly and dries out afterwards. Seal a foil faced board hard onto the inside of it and the wall can only dry outwards, so in a driven rain winter it stays wet and the dew point ends up inside the build up. That is interstitial condensation, and it rots joist ends quietly for years before anything shows. BS 5250 is the code of practice that deals with it. On old masonry we favour a breathable lining, wood fibre or a mineral wool build up with a vapour open finish, so moisture can still pass.
The junctions decide it. A lined wall that stops at the plaster line leaves a cold bridge at every window and door reveal, at the floor junction and at the party wall. Those are where black mould appears afterwards. Reveals get returned with a thin board, often aerogel backed where the frame leaves no room, and the lining is carried past the junction.
External wall insulation, and where it is not an option. Boards, a render carrier and a thin coat finish outside gives the best U value and no loss of room, but it buries the stone. On a stone elevation in the conservation area that is not a realistic proposal, and we will say so rather than take you through an application that will fail.
Cavity work on the newer houses. Post war housing in the village does have a cavity, and where the borescope shows it clear and dry it takes bonded bead or blown mineral wool in a day. Failed or slumped fill is extracted through the drilled holes and replaced. Whatever the wall, we look at extract fans and trickle vents in the same visit, because airtightness without ventilation is how you make a mould problem.
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.
Langton Matravers Conservation Area covers the village, so appearance is controlled and any external wall insulation is a planning application rather than a free choice, which the Planning Portal guidance on external walls explains. Internal lining is invisible from the road and needs no permission, as the Planning Portal page on insulation confirms. There are 50 listed entries in the parish, and on a listed building internal work needs listed building consent too. Dorset Council handles both, and building control comes in under regulation 23 once you renovate a thermal element.
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 stone cottage on the main street, a post war semi off it and a bungalow with a rendered outer leaf are three different surveys. 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. The village is under ten miles from us and we are in Swanage and Corfe most weeks. The phone is answered 24 hours for emergencies; scheduled work runs Monday to Friday, 8am to 6pm.
Worth knowing
A Purbeck wall has to be allowed to dry
Purbeck limestone laid in lime mortar behaves nothing like a modern cavity wall. It takes water in through the face in a wet south westerly, holds it, and gives it back through both faces once the weather turns. The wall has done that for two hundred years. What it cannot cope with is being sealed on one side.
This changes the specification in one way. The cheapest internal lining on the market is a foil faced PIR board dabbed straight onto the wall, and on a solid stone elevation facing the weather it is the wrong product. The foil is a vapour barrier on the warm side, the dabs leave voids behind the board, and warm moist air finds the cold masonry through the gaps at the edges. What comes back is damp at the skirting and mould on the reveals.
So on stone we line with a build up that stays vapour open, fixed to battens rather than dabs so there is no unventilated void, and we sort the outside first. Repointing in lime rather than cement, a working gutter and a downpipe that is not soaking one patch of wall take more heat loss out of a cottage than the first 25mm of insulation does, and the payback is quicker. So is an afternoon spent on the draughts around the doors.
Who you are dealing with
A local firm you can check
We cover Langton Matravers, Kingston, Worth Matravers and the BH19 addresses around them, 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
Langton Matravers questions we get asked
Can a Purbeck stone wall be cavity filled?
No. It is a solid wall with no cavity in it, so there is nothing for the bead or the fibre to go into. Drilling it only puts holes in good stonework.
What is the best insulation for a solid stone wall?
Something vapour open, fixed to battens rather than dabbed on. Wood fibre or a mineral wool build up lets the wall carry on drying inwards, which a foil faced board does not.
How much room will an internal lining take off?
Between 60 and 100mm on each wall that gets done, less at reveals where we use a thinner high performance board. We set it out before ordering so you can see what it does to the room.
We are in the conservation area. Can we insulate outside?
Almost certainly not on a stone elevation. External insulation buries the stone and changes the appearance, which is exactly what the designation controls. Internal lining is the route that gets consent.
Can we line one room at a time?
No, and we usually advise against it. Start with the coldest rooms on the weather side, live with it a winter, then decide. It also keeps the house usable, and it still shows on an EPC.
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Find out what your walls are made of first
Thomas comes out, works out whether you have stone, solid brick or a cavity, and prices only the work that suits it. The visit and the written quote are both free.