Warm roof insulation upgrades across Surrey

Guide price

£3,100–£5,350

Survey

Free for new and replacement roofs

Quote

Fixed, in writing

Coverage

England, Wales, Scotland, NI

How much does a warm roof upgrade cost in Surrey?

Guide prices including VAT at South East rates. The fixed price comes after a free survey for new and replacement roofs.

Which flat roofs are common in Surrey?

Flat roofs in Surrey sit on low-rise post-war blocks of flats, terraced streets with flat-roofed rear kitchens and bathrooms and lock-up garage blocks on estates. 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. Approximate 1991–2020 regional averages based on Met Office data.

Building regulations in England

Replacing more than half of a roof over a heated room usually counts as renovating a thermal element, so it is insulated to current standards and notified to building control. Renovated roofs over heated rooms are insulated to around 0.16 W/m²K where that's feasible, and new extension roofs are built to 0.15 W/m²K. In Surrey the application goes to Woking Borough Council, Guildford Borough Council, Elmbridge Borough Council and 8 other councils. More on the rules.

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.

Can a cold flat roof be converted to a warm roof?

Yes, and it is the usual approach when an older cold roof is re-covered. The old covering is stripped, the deck is checked and replaced where needed, and the vapour control layer, insulation and new waterproofing go on top.

The existing insulation between the joists is assessed at the same time. Leaving it in place can create a cold, unventilated gap that traps moisture, so it is often removed or the build-up is designed so that most of the insulation sits above the deck. We decide this case by case once we can see inside the roof. If the covering is still sound and you are only patching it, the upgrade isn't usually required, and our repair or replace guide explains how to decide between the two.

Which towns in Surrey do we cover?

• Woking
• Guildford
• Esher
• Redhill
• Staines-upon-Thames
• Banstead
• Leatherhead
• Ewell
• Farnham
• Epsom
• Camberley
• Egham
• Sunbury-on-Thames
• Ashford, Surrey
• Godalming
• Reigate
• Horley
• Caterham
• Weybridge
• West Molesey
• Dorking
• Haslemere
• Cobham
• Chertsey

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