Farnham at a glance
- Postcode districts
- GU9, GU10
- Population
- about 36,971 (GeoNames)
- Council area
- Waverley Borough Council
- Building approval
- Waverley Borough Council building control, or a registered building control approver
- Nearest main town
- Woking, about 13 miles
- Guide price region
- South East (+10% on West Midlands rates)
Why upgrade to a warm roof in Farnham?
Converting a garage, loft space or outbuilding to a room in Farnham changes what the roof needs to do. Once the space is heated, the roof is expected to perform to a higher standard, and a warm build-up is usually the simplest way to get there.
In and around Farnham, flat roofs are typically found on terraced streets with flat-roofed rear kitchens and bathrooms, and on bungalows with flat-roofed side extensions and dormers. Much of the South East sits in the drier Thames catchment at roughly 730 mm of rain a year, so the usual failures are at joints, upstands and outlets rather than from sheer volume of rain.
How much does a warm roof upgrade cost in Farnham?
Guide price in Farnham: £3,100–£5,350 for a 20 m² extension roof in EPDM with a new deck and insulation, including VAT at South East rates. The fixed price comes after a free survey for new and replacement roofs.
| Job | Guide price inc VAT |
|---|---|
| Extension (20 m²), EPDM, new deck + insulation | £3,100–£5,350 |
| Extension (20 m²), EPDM with sedum green roof | £4,850–£8,900 |
Will insulating the roof raise its height, and what about doors and upstands?
Yes. A warm roof makes the roof thicker, often by more than 100 mm depending on the insulation and the U-value target. That extra height is the main thing we plan around.
Waterproofing at a wall usually needs to rise about 150 mm above the finished roof surface, so if the roof gets higher, the upstand has to go higher too. That can be a problem where the roof meets a door threshold, a low window sill, a cavity tray or a rooflight kerb. At the edges, trims and fascias are reset to the new level, and gutters may need to move.
Where there isn't enough height, the options include using thinner, higher-performance insulation, lowering the deck where the structure allows, raising the sill or threshold, or, where it is genuinely not feasible to reach the full target, insulating as far as is reasonable and recording why with building control. We work this out at the survey so there are no surprises on the day.
What's included?
- Rigid insulation boards sized to the U-value target
- Vapour control layer on the warm side of the insulation
- New waterproofing, with a written workmanship guarantee
- Survey of the deck, joists and existing insulation
Building regulations in England
Replacing more than half of a flat roof over a heated room usually counts as renovating a thermal element, so the roof is insulated to around 0.16 W/m²K where that's technically and economically feasible, and the work is notified to building control: the council or a registered building control approver, unless a registered competent person self-certifies it. A roof on a new extension is built to 0.15 W/m²K. Patch repairs, and most unheated detached garages, don't trigger the upgrade. Structural changes, or a new covering that adds 15% or more to the roof's weight, also need approval. More on the rules.
Which nearby areas do we also cover?
Warm roof insulation upgrades in Farnham: questions
Do you cover Farnham?
Yes. Farnham is part of our Surrey coverage, including postcode districts GU9, GU10. Surveys and roofs are carried out by vetted roofing teams working under S&K Property Investments and Improvement Ltd.
Who checks building regulations for a flat roof in Farnham?
Where the work needs approval it goes to Waverley Borough Council building control, or a registered building control approver. We tell you at the survey whether your job needs it and deal with the paperwork as part of the quote.
How much does a warm roof upgrade cost in Farnham?
£3,100–£5,350 for a 20 m² extension roof in EPDM with a new deck and insulation, at South East guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
Does a warm roof stop condensation?
It greatly reduces the risk by keeping the deck warm and placing a vapour control layer on the warm side. Good ventilation in kitchens and bathrooms below still helps.
Is a warm roof worth it on a garage?
On a detached, unheated garage, usually not, as there is no heated space to protect and the thermal rules don't normally apply. On an integral or heated garage, or one being converted into a room, it is.