Group A · Loft and roof insulation
Cold deck flat roof upgrade
Insulation fitted between the joists from below, only where a warm deck isn't possible.
Priced after survey
Cold deck flat roof upgrade
Every job like this is different, so we measure first and give you a fixed written quote. The price depends on:
- The area and access
- What's there now and its condition
- The system and finish you choose
No obligation — your survey confirms what suits and what it costs.
- Best for
- Limited-access roofs
- Guarantee or standard
- Condensation risk analysis
- Time on site
- Most lofts are done in a day or less.
- Typical price
- Priced after survey
What it is
What is cold deck flat roof upgrade?
Insulation fitted between the joists from below, only where a warm deck isn't possible.
Best for: Limited-access roofs.
Who it suits
Which homes is cold deck flat roof upgrade suitable for?
Is my home suitable?
Pick your property type for a straight answer on cold deck flat roof upgrade.
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
Insulation between joists from below with ventilation, only where a warm deck is not possible.
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 cold deck flat roof upgrade cost?
Priced after survey
Jobs like this vary too much for a fair online price, so we measure first and give you a fixed written quote — with no obligation.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
Most lofts are done in a day or less. Roof, flat roof and room-in-roof work takes longer and is confirmed at survey.
Disruption
Moderate — the ceiling below is taken down and replaced, so the room underneath is out of use while we work.
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
Condensation risk analysis. 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
Cold deck flat roof upgrade: your questions answered
What is a cold deck flat roof?
A flat roof insulated between the joists from below, with the deck above left cold. It needs a ventilated gap and a vapour control layer to manage moisture.
Why only do a cold deck where a warm deck isn't possible?
Cold decks carry a higher condensation risk. We use them only where the roof can't be raised or re-covered, and only after a condensation risk analysis.
Is a cold deck installed from inside?
Yes — the ceiling below is taken down, the joists insulated and ventilated, then a vapour control layer and new ceiling fitted.
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.
Loft insulation top-up
An extra cross-layer over existing insulation to reach the recommended 270 mm or more.
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.
Begin your project
Ready to talk about cold deck flat roof upgrade?
Tell us about your home and we'll arrange a survey, then a fixed written quote — no obligation.