Wall insulation in Longham
A detached house on open ground takes weather on all four walls, and that decides what should go in the cavity and what should stay out of it.
The site visit is free and so is the written itemised quote. Thomas Hannen prices every job himself.
Nearly half the houses here are detached and stand on open plots beside the water meadows, which means all four elevations take weather instead of one. That changes what should go in a cavity, and on the worst wall it can change whether the cavity ought to be filled at all.
The three calls we get are a south west facing wall that has gone patchy and cold since it was filled, a bungalow that never feels even from one end to the other, and somebody comparing two quotes where one says bead and the other says wool and neither explains why.
We settle it by looking. One small hole in a mortar joint, a borescope through it, moisture readings on the inside face, and a walk round to see which elevation is taking the driving rain. Then a free written itemised quote, with the survey, the system, the junctions and the making good on separate lines.
The work
Filling a wall that has weather on every side
The check that decides it. A nine inch solid wall and an early brick and block cavity are indistinguishable from the drive. So we drill a small hole in a mortar joint and put a borescope in: is there a gap, how wide, is it clear, is it dry, has anything been in it. On an exposed house we also look at the state of the outer leaf, because that is what stands between the fill and the rain.
Cavity wall insulation, and the choice of material. Bonded polystyrene bead is usually the right answer on an exposed wall. It flows into the corners, it does not slump, and it is far less inclined to wick water across the gap than a fibre. Blown mineral wool is cheaper and perfectly sound on a sheltered elevation, which on a detached house often means only one or two of the four. Fill goes in from outside through drilled holes made good in matching mortar.
When we say leave it empty. A cavity that is under fifty millimetres, one with mortar droppings bridging the ties, a cracked or badly pointed outer leaf, or any sign of water already crossing, and filling it moves the problem inside. On the most exposed wall of an isolated house the honest answer is sometimes to repoint and repair first and insulate that elevation on the inside instead.
Internal wall insulation. IWI is the route for a solid wall and the fallback for a cavity we will not fill: insulated plasterboard bonded on, or batten and stud with mineral wool or PIR between, boarded and skimmed. Celotex and Kingspan buy more per millimetre, aerogel board suits a tight room. Reveals, threshold, floor junction and joist ends are wrapped, because the heat loss in a lined room concentrates at the edges.
External wall insulation. EWI is board on the outside face with a render carrier and a thin coat over it. On an exposed house it does two jobs at once, insulating and weatherproofing, and it takes the thermal bridge out at eaves and corners. It thickens every reveal and pushes sills and rainwater goods outwards, so it is a bigger piece of work than a fill.
Old fill, and ventilation. A slumped cavity leaves a cold band at the head of the wall; a wet cavity carries penetrating damp inside and black mould with it. The borescope reads both and extraction comes first. Then the air: trickle vents, a working extract fan, any air brick that has been blocked. Insulating shifts the dew point and removes the draughts, so a taped vapour control layer and breathable materials keep interstitial condensation out of the build up.
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.
Lining the inside of a wall is not development and needs no application, which Planning Portal guidance on insulation confirms; insulating or cladding the outside face is a bigger question and Planning Portal guidance on external walls sets out when permission is needed. There is no conservation area over the village, though there are listed entries in the parish and Dorset Council's listed building pages is where to check. It stays notifiable work: regulation 23 means a renovated thermal element has to reach the Part L standard in Approved Document L, and building control take the U value and the ventilation together.
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 detached house on an open plot, a bungalow behind a hedge and a pair of cottages on the main road 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. It is under five miles from us, so a BH22 address off the main road is usually seen within a day or two. The phone is answered 24 hours for emergencies; scheduled work runs Monday to Friday, 8am to 6pm.
Worth knowing
Driven rain, and why an exposed wall gets a different fill
A cavity was invented to break the path water takes through a wall. Rain soaks the outer leaf, runs down the inside face of it and drains back out, and the inner leaf stays dry. Put the wrong material in that gap on a wall that regularly takes driven rain and you hand the water a bridge, which is why a filled wall on an open plot can start showing damp patches inside that it never had before. BS 8104 is the code that sets out how you assess a wall's exposure to wind driven rain, and on the open ground beside the meadows the south west elevation is in a different class from the sheltered side of the same house.
In practice that means treating the elevations separately rather than quoting a house as one number. Bead on the exposed walls, wool where it is sheltered if that is what suits the budget, and on the worst wall of all sometimes nothing in the cavity and a lining on the inside instead. It also means the outer leaf gets looked at first: open joints and a cracked render let water in faster than any fill can cope with, and repointing that wall is the cheaper half of the job.
Who you are dealing with
A local firm you can check
We cover Longham, the Ham Lane side, Hampreston and the BH22 addresses around them, with Dorset Council for planning and building control. 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
Longham questions we get asked
Can filling a cavity make a wall wetter?
It can, on an exposed elevation with the wrong material or a poor outer leaf. The fill gives water a path across a gap that was there to stop it, which is why the survey looks at exposure.
Why bead on one wall and wool on another?
Because the walls are not in the same weather. Bead resists carrying water across and holds its shape, so it suits the elevations that take driving rain. Wool is fine where it is sheltered.
Should the pointing be done before the walls are insulated?
On an exposed wall, yes. Open joints let far more water into the outer leaf than any fill can handle, and it is cheaper to sort the rain out before you close the gap.
Is it worth insulating just the cold end of the house?
Often, as long as the junctions where the work stops are detailed. An untreated edge next to a treated one becomes the new cold spot and shows up as condensation.
How many days for a detached house on an open plot?
A day for most, including making good the drilled holes. Larger properties with awkward elevations and a lot of corners can run into a second.
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Get the exposed wall assessed, not assumed
Thomas comes out, scopes the cavity, looks at what the weather does to each elevation and prices it in writing. The visit and the quote are free.