The short answer
Loft insulation in the UK typically costs around £5 to £30 per square metre depending on the method. Simple rolled mineral wool laid in an empty loft is the lowest-cost option — often £5–£12/m² for materials and basic fitting. Blown insulation by a professional usually lands around £10–£20/m², while boarding plus insulation for a usable storage floor runs higher, roughly £25–£50/m². These are indicative figures: access, clearing old material and the current 270mm depth standard all shift the total.
A per-square-metre figure is the fairest way to compare loft insulation quotes, but the headline rate hides several variables. Here is what sits behind the number.
Per-m² cost at a glance
- Rolled mineral wool (DIY/basic)£5–£12/m²
- Blown loose-fill (pro)£10–£20/m²
- Boarded + insulated floor£25–£50/m²
- Recommended depth270mm mineral wool
- VAT on insulation0% to 31 March 2027
What the per-square-metre price includes
When an installer quotes a rate per square metre, they are usually rolling together the insulation material itself, any vapour or breather layers, and the labour to lay it to the recommended depth. The current UK standard for a cold loft is 270mm of mineral wool (or the equivalent in other materials), which is what delivers a roof U-value in line with current expectations under Part L of the Building Regulations. Topping up a loft that already has 100mm to bring it to 270mm costs less per square metre than insulating bare joists from scratch, because less material and time are involved.
Most UK lofts are between 30m² and 60m² of floor area, so a per-m² rate of £10 translates to a few hundred pounds for a typical semi or terrace. Bear in mind that the usable area is the floor footprint, not the sloping roof, and that fiddly corners around the eaves reduce the proportion you can actually lay to full depth.
Why the rate varies so much between lofts
The same installer can quote very different per-m² figures for two houses. The factors that move it are practical rather than mysterious:
- Access — a tight hatch, no fixed ladder or a low roofline slows the job and pushes the rate up.
- Existing insulation — a clean top-up is cheaper than stripping out old, degraded or contaminated material first.
- Method — blown loose-fill needs specialist equipment; rolled wool needs only hands and time.
- Obstructions — water tanks, cabling, downlighters and stored belongings all add labour.
- Boarding — if you want a walkable storage floor, raised battens and boards add materially to the m² rate.
| Method | Typical cost per m² | Notes |
|---|---|---|
| Rolled mineral wool | £5–£12/m² | Lowest-cost; easy DIY in an empty loft |
| Blown loose-fill | £10–£20/m² | Professional only; good for awkward spaces |
| Sheep's wool / natural | £15–£30/m² | Breathable; higher material cost |
| Boarded + insulated floor | £25–£50/m² | Includes raised deck for storage |
Indicative UK figures for guidance, 2026. Actual quotes vary by region, access and loft condition.
DIY versus professional per square metre
Buying rolls of mineral wool from a builders' merchant and laying them yourself is the lowest-cost route on a pure materials basis — often under £6/m² for the wool alone. The trade-off is the manual work in a hot, dusty, awkward space, and the need to leave gaps around recessed lights and to maintain ventilation at the eaves. A professional rate is higher because it bundles in labour, waste disposal, correct detailing and, often, a guarantee. For blown insulation there is no realistic DIY option: the loose-fill is injected with a machine, so you are always paying a professional rate.
Because insulation currently attracts 0% VAT on supply-and-fit in Great Britain until 31 March 2027, the gap between a professional installed price and a DIY price is narrower than it once was — the VAT relief applies to the installer's bill, removing the 20% that would otherwise sit on labour and materials together. A DIY purchase of materials alone does not get the same zero rate, so the saving from doing it yourself is mostly the labour, not the VAT.
Turning a per-m² rate into a real budget
To move from a per-square-metre figure to a number you can plan around, measure the loft floor and be honest about how much of it can be insulated to full depth. The footprint near the ridge is easy to reach; the triangular space at the eaves is not, and you should not pack insulation hard against the eaves anyway because that blocks the ventilation the roof needs. A practical rule is that the usable insulating area is a little less than the raw floor measurement once you allow for the eaves margin and any boarded or obstructed sections.
It also helps to separate the quote into its parts. Ask the installer to show the material, the labour, any removal or disposal of old material, and any boarding as distinct lines. A single blended per-m² rate can hide whether the price assumes a clean top-up or a full strip-out, and itemising lets you compare two quotes that look superficially similar. Where one installer quotes notably below the typical range, the difference is usually that they are laying to a shallower depth than 270mm, excluding disposal, or assuming the existing layer stays — so confirm exactly what the figure buys before choosing on price alone.
Frequently asked questions
Is it cheaper per square metre to insulate a larger loft?
Often slightly, yes. Fixed costs like setting up, travel and clearing the hatch are spread over more area, so the effective per-m² rate can fall a little on a big loft compared with a small one.
Does the per-m² price include removing old insulation?
Not always. A straight top-up quote assumes the existing material stays. If old insulation is degraded, damp or contaminated and needs removing, that is usually a separate line item — always ask.
How many square metres does a typical UK house loft have?
Most semis and terraces have around 30–50m² of loft floor, while a larger detached house may have 60m² or more. Measure the floor footprint, not the sloping roof area, to estimate your cost.
Sources & further reading
Figures on this page are typical UK ranges drawn from published sources and depend on your specific loft. They are guidance, not a quotation.