London & South-East England
Room in Roof Insulation
Warm loft rooms and dormers, insulated from inside by our own team while you carry on living there.
Is room in roof insulation right for your home?
- Loft conversions from the 1970s to the 2000s with thin or no rafter insulation
- Rooms in the roof that are cold in winter and overheat in summer
- Dormer bedrooms with condensation or mould at the cheeks and eaves
- Houses being insulated as a whole, where the loft room is the last cold space
- Bungalows and chalet bungalows where the bedrooms are in the roof
Room in Roof Insulation: key facts
- A room in the roof has four cold surfaces: the sloping ceilings, the flat ceiling, the stud walls to the eaves and the dormer cheeks. All four need insulating or the room stays cold.
- A typical loft room costs £3,000 to £7,500 to insulate, from our quote book.
- SWIP RIR insulated plasterboard (50 mm PIR bonded to 12.5 mm plasterboard, 62.5 mm in total) is £140/m² fitted over the existing ceiling.
- PIR between and under the rafters keeps a 50 mm ventilation gap behind the insulation so the roof timbers stay dry.
- Dormer roofs can be insulated from outside at £120/m², without disturbing the room below.
- Installed at 0% VAT until 31 March 2027 by our own PAS 2030:2023 certified team.
What is room in roof insulation?
Room in roof insulation treats a converted loft or a room built into the roof, where the walls and ceilings are the roof itself. Heat leaves through the sloping ceilings, the small flat ceiling at the top, the short stud walls that back onto the eaves and the cheeks of any dormer. We insulate each of those surfaces, either with rigid PIR board between and under the rafters or with an insulated plasterboard fixed over the existing lining.
London and the South-East have a large stock of loft conversions from the 1970s onwards, and older houses with a room in the roof from the start. Many were finished with 25 to 50 mm of insulation or none at all. The room is cold in winter, too hot in summer and often has condensation or mould behind the eaves cupboards. Because the roof is the largest surface in the room, it is usually the biggest single heat loss in the house once that room is heated.
We survey the room, check the rafter depth and the ventilation path, and quote for the whole envelope rather than one surface. Most work is done from inside, one surface at a time, with the boards fixed through the existing plasterboard so the room stays usable. Where a dormer roof is flat and due for a new covering, we insulate it from outside as a warm deck. Our own team fits, plasters and finishes ready for decoration.
Who does the work
Room in roof insulation is installed by our own trained team under our PAS 2030:2023 certification for roof insulation. We are a SWIP approved installer, so the SWIP RIR insulated plasterboard system is fitted, plastered and finished by the same crew.
Room in Roof Insulation cost guide
Indicative 2026 pricing from our quote book for London and the South-East. Every quote is free, fixed and itemised after a survey.
| Job type | Indicative cost |
|---|---|
| SWIP RIR insulated plasterboard, 62.5 mm | £140 / m² |
| PIR between and under the rafters | £90 – £140 / m² |
| Dormer roof insulation from outside | £120 / m² |
| Loft roll to the flat ceiling and residual loft | Itemised |
| Typical loft room, all four surfaces | £3,000 – £7,500 |
VAT: 0%. Roof insulation is an energy-saving material, so the installation is charged at 0% VAT until 31 March 2027 (HMRC VAT Notice 708/6). The plaster finish over the boards is part of the install and is charged at the same rate.
Systems and materials we install
How room in roof insulation works
Free survey
We measure the sloping ceilings, stud walls, flat ceiling and dormer cheeks, check the rafter depth and confirm the eaves ventilation path is clear.
Fixed quote
A written, itemised quote within 24 hours showing the system for each surface, the thickness and the U-value it achieves.
Installation
Boards are fixed through the existing lining into the rafters and studs, or the lining is stripped and PIR fitted between and under the rafters. Joints are taped and the surfaces plastered.
Sign-off and guarantee
Final inspection, photographs of the build-up, a Building Regulation certificate and a written guarantee for the insulation.
Free survey & fixed quote
Book a free, no-obligation survey and we will send a clear, fixed written quote. One point of contact from survey to sign-off, and a written guarantee on the work.
Get a free quoteRoom in Roof Insulation FAQs
How much does room in roof insulation cost?
Do I have to move out while the work is done?
Why does the roof need a ventilation gap?
Between the rafters or over the existing ceiling?
How much room height will I lose?
How long does it take?
Areas we cover
We arrange room in roof insulation across Greater London, Surrey, Kent and Hertfordshire. See all areas we cover →
Related guides
In-depth, independent guidance to help you decide.
Last reviewed September 2026 by Stay Warm Insulation.
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