The short answer
Insulating a loft to the recommended 270mm with mineral wool typically costs around £300–£1,800 in the UK, depending on the size of the loft and the property. As a rough guide that works out at roughly £200–£500 for a flat or small one-bed, £300–£700 for a two-bed terrace, £500–£1,200 for a three-bed semi, and £900–£1,800 for a four-bed detached. A top-up over thinner existing insulation sits at the lower end (often £300–£700), while a fresh install into a bare loft and any awkward access push it higher. The main drivers are loft area, how much insulation is already there, access, and the material.
Price depends mainly on how big your loft is, whether you're topping up or starting from bare, and how easy it is to get around up there. The figures below are typical installed prices for guidance, not quotations.
Typical UK costs (to 270mm)
- Flat / small one-bed~£200–£500
- Two-bed terrace~£300–£700
- Three-bed semi~£500–£1,200
- Four-bed detached~£900–£1,800
- Top-up over existing~£300–£700
What drives the price
- Loft area: you pay largely by the square metre covered, so a larger roof footprint costs more — a detached home has far more loft to fill than a mid-terrace.
- Top-up vs fresh install: topping thinner existing insulation up to 270mm is cheaper than insulating a bare loft from scratch.
- Access & obstructions: a cramped loft, low headroom, stored belongings or lots of pipework and wiring all add labour time.
- Material choice: mineral wool rolls are the common, lowest-priced route; blown insulation or rigid boards for a warm-loft conversion cost more (see the thickness page).
| Property | Typical figure | Notes |
|---|---|---|
| Flat / small one-bed | ~£200–£500 | smallest loft area |
| Two-bed terrace | ~£300–£700 | often a quick single-day job |
| Three-bed semi | ~£500–£1,200 | common UK average ~£930 |
| Four-bed detached | ~£900–£1,800 | largest loft footprint |
Indicative UK figures for guidance. Sources: Checkatrade and MyJobQuote / MyBuilder cost guides.
Why a top-up costs less than a fresh install
If your loft already has some insulation but it's below the modern 270mm standard, an installer simply lays more on top to bring it up to depth — less material, less time and no clearing of a bare deck. That's why a top-up often falls to around £300–£700 while a full fresh install runs higher. Most standard mineral-wool jobs are completed in a single day, with day labour rates around £200–£300, so the bulk of the cost is material and area rather than long labour.
Want a measured loft insulation quote?
We'll match you with a TrustMark-registered insulation installer who measures your loft and quotes on a clear specification — depth, material, area and any access works set out.
Frequently asked questions
How much does it cost to insulate a loft?
Insulating a loft to 270mm with mineral wool typically costs around £300–£1,800 depending on the property — roughly £300–£700 for a two-bed terrace and up to £900–£1,800 for a four-bed detached. A top-up over thinner existing insulation sits at the lower end.
Is a loft insulation top-up cheaper than a fresh install?
Yes. Topping existing insulation up to 270mm uses less material and time, so it often falls to around £300–£700, while insulating a bare loft from scratch costs more.
Why is the price range so wide?
Because lofts differ. The area to cover, how much insulation is already there, and how easy the loft is to access all move the figure. A measured quote gives the accurate number for your home.
Sources & further reading
- Checkatrade — loft insulation cost guide (2026)
- MyBuilder — how much does loft insulation cost (2026)
Figures on this page are typical UK ranges drawn from published sources and depend on your specific loft. They are guidance, not a quotation.