Group A · Loft and roof insulation
Loft insulation top-up
An extra cross-layer over existing insulation to reach the recommended 270 mm or more.
Price by property type
Loft insulation (new or top-up)
- Mid-terrace£500–£1,000
- Semi / end-terrace£600–£1,300
- Detached£900–£1,800
- Bungalow£900–£2,000
- Flat / block£400–£900top floor
Before grants · updated 11 October 2026 · a survey confirms the final figure.
- Best for
- Lofts with 50–150 mm
- Guarantee or standard
- Part L
- Time on site
- Usually a few hours to a day for a typical house.
- Typical price
- From £400
What it is
What is loft insulation top-up?
An extra cross-layer over existing insulation to reach the recommended 270 mm or more.
Best for: Lofts with 50–150 mm.
Build-up
Loft insulation
Cold, ventilated loft
Warm room below
- 1Cross layer laid over the joistsSecond roll laid at right angles
- 2First layer between the joists
- 3Ceiling
Mineral wool to 270–300 mm, with the eaves kept clear for ventilation.
Who it suits
Which homes is loft insulation top-up suitable for?
Is my home suitable?
Pick your property type for a straight answer on loft insulation top-up.
Guidance only — every home is different, and a survey confirms what suits yours.
Houses
- Detached house
- Semi-detached house
- End-of-terrace
- Mid-terrace
- Townhouse
- Mews house and cottage
- Detached bungalow
- Semi and terraced bungalow
- Chalet and dormer bungalow
- Period home
- 1930s home
- Post-war and ex-council house
- Non-traditional / system-built
- Listed building or conservation area
- Farmhouse, barn conversion or rural home
- New build or self-build
Flats and blocks of flats
Commercial and public buildings
Usually suitable Depends — a survey confirms
Not usually suitable for 1 property type
- Park and mobile home — Park and mobile homes need specialist systems, which we arrange through a partner rather than standard measures.
Materials and brands
What we use
Extra cross-layer of Knauf or Rockwool roll over existing insulation to reach 270 mm+.
Insulation brands we work with
- Knauf Insulation (Earthwool, Supafil blown)
- Rockwool
- Superglass
- Isover
- Kingspan
- Celotex
- Recticel
- Xtratherm
- Steico wood-fibre
- YBS and Actis multifoil
The exact system and brand for your home are confirmed in your written quote.
Heat, bills and EPC
What it does for your heat loss, bills and EPC
Heat rises, so a poorly insulated roof is often the largest single route out for heat. Insulating it lowers the roof's U-value — how easily heat passes through — so the heating runs less and the EPC rating usually improves. The gain is largest where there's little insulation now; topping up a loft that's already reasonably insulated gains less.
See the EPC points and savings for your home in the EPC plannerU-value before and after, typical heat and bill saving, and EPC points — worked out for your property.Price
How much does loft insulation top-up cost?
Prices change with your property type. Pick your column — the quote builder then refines it for your home.
| Measure | Mid-terrace | Semi / end-terrace | Detached | Bungalow | Flat / block |
|---|---|---|---|---|---|
| Loft insulation (new or top-up) | £500–£1,000 | £600–£1,300 | £900–£1,800 | £900–£2,000 | £400–£900top floor |
Indicative ranges for London and the South East, supplied and installed, including VAT, before grants. Updated 11 October 2026. A survey confirms your final price.
0% VAT on energy-saving materials
Insulation, solar panels, batteries and heat pumps installed in homes in Great Britain are zero-rated for VAT until 31 March 2027. Windows and doors are not included.What to expect
Time on site, disruption and approvals
Time on site
Usually a few hours to a day for a typical house.
Disruption
Low — the work happens in the loft or roof space. We need clear access to the hatch, with stored items moved to one side.
Planning and building control
Loft insulation doesn't need planning permission or building control. Re-roofing, flat roof replacement and turning a roof space into a room must meet Building Regulations Part L, and we handle the notification.
Guarantee and standard
Part L. The guarantee and certification for your job are confirmed in writing in your quote.
60-second grant check
Could a grant help pay for it?
Grant eligibility checker
About 60 seconds · plain results: likely, possibly or not eligible
Before we start
What type of property is it?
Questions
Loft insulation top-up: your questions answered
How much does loft insulation top-up cost?
Typical installed prices in London and the South East, including VAT and before any grant: £500–£1,000 for a mid-terrace; £600–£1,300 for a semi-detached or end-of-terrace house; £900–£1,800 for a detached house; £900–£2,000 for a bungalow; £400–£900 for a flat (top floor). Prices updated 11 October 2026. A survey confirms your final figure.
How do I know if my loft needs a top-up?
Measure the depth: if the insulation sits level with or below the top of the joists — often 50–150 mm in older lofts — a top-up will help. If it's already 270 mm or more and in good condition, there's little to gain.
Do you remove the old insulation first?
Not if it's dry and in reasonable condition — we lay a new cross-layer over it. If it's damp, compressed, contaminated or rodent-damaged, loft clearance and replacement is the better option.
Is a loft top-up worth it?
It's usually worth it if you have less than about 150 mm now. The less insulation there is today, the bigger the improvement in comfort, bills and EPC.
Group A
More in loft and roof insulation
Loft insulation
Mineral wool laid between and across the joists to 270–300 mm so heat stays in the rooms below.
Blown loft insulation
Loose-fill insulation blown into awkward, shallow or low-headroom lofts that rolls can't reach.
Loft clearance and replacement
Old, damp or damaged insulation removed, the loft cleaned, then new mineral wool fitted.
Raised loft boarding and storage
Loft legs or raised boarding over full-depth insulation, so storage doesn't crush it.
Insulated loft hatch and ladders
An insulated, draught-sealed hatch and loft ladder — a small add-on that stops a big leak.
Room-in-roof insulation
Insulating the sloping ceilings, stud walls, flat ceiling, gables and dormer cheeks of an attic room.
Begin your project
Price loft insulation top-up in two minutes
See a price range for your property type, with grants and 0% VAT applied where they fit. A survey always confirms the final figure.