- Guide price
- £2,950–£5,150
- Survey
- Free for new and replacement roofs
- Quote
- Fixed, in writing
- Coverage
- England, Wales, Scotland, NI
Cambridgeshire at a glance
- Largest towns
- Peterborough, Cambridge, Wisbech, St Neots
- Postcode areas
- CB, PE
- Building control
- Peterborough City Council, Cambridge City Council, Fenland District Council and 2 other councils
- Neighbouring areas
- Northamptonshire · Bedfordshire · Hertfordshire · Suffolk
- Guide price region
- East of England (+5% on West Midlands rates)
How much does a new extension roof cost in Cambridgeshire?
Guide prices including VAT at East of England 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 | £2,950–£5,150 |
| Extension (20 m²), GRP, new deck + insulation | £3,150–£5,650 |
| Extension (20 m²), EPDM, insulation + 1 rooflight upstand | £3,150–£5,500 |
| Single garage (18 m²), EPDM rubber | £1,700–£2,950 |
Which flat roofs are common in Cambridgeshire?
Flat roofs in Cambridgeshire sit on shops with flat-roofed rear stores below flats, bungalows with flat-roofed side extensions and dormers and newer estates where the first extension roofs are now being replaced. The East of England is the driest part of Britain, with parts of the Anglian region around 630 mm a year, so summer heat and UV, not rainfall, do most of the ageing on a felt roof. 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 Cambridgeshire the application goes to Peterborough City Council, Cambridge City Council, Fenland District Council and 2 other councils. More on the rules.
Why does water pond or leak where the extension meets the house?
Usually because the fall runs the wrong way, the abutment detail has failed, or the roof has sagged close to the wall. The junction with the house is the most common leak point on an extension roof.
If the roof falls towards the house, or the deck dips near the wall, water sits against the upstand and finds any weakness in the flashing above. Older roofs often have the felt simply turned up the brickwork with no cover flashing, or a flashing that has pulled out of its joint. A patch will not change a fall. We re-firr or use tapered insulation so water runs away from the wall, then form a new upstand, usually 150 mm above the finished roof, with a flashing chased into the mortar joint.
Rooflights and lanterns are the other weak point. A lantern needs a properly built kerb with the membrane dressed up and under its frame. We rebuild rooflight upstands within the roof job; we do not supply the lantern itself. Our guide to ponding water explains the causes in more depth.
How long will my kitchen be disrupted by a new roof?
Most single-storey extension roofs are replaced in two to four working days, depending on size, rooflights and weather. The kitchen usually stays in use throughout.
Expect noise during the strip-out, and occasional dust through gaps around old rooflights, so it helps to cover worktops and move anything fragile off high shelves. We strip only what we can make weathertight by the end of each day. If a rooflight or lantern is being lifted and refitted, there may be a temporary cover over the opening for a short time. Resin systems smell while they cure, so keep the windows below the roof closed on that day.
Which towns in Cambridgeshire do we cover?
Extension and kitchen roofs in Cambridgeshire: questions
Which towns in Cambridgeshire do you cover?
All of Cambridgeshire. The main towns have their own pages below, and if yours isn't listed we still cover it: send your postcode and we'll confirm.
How much does a new extension roof cost in Cambridgeshire?
£2,950–£5,150 for a 20 m² extension roof in EPDM with a new deck and insulation, at East of England guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
Which postcode areas do you cover in Cambridgeshire?
All of Cambridgeshire, including the CB, PE postcode areas. Send your full postcode and we'll confirm.
Can you keep my existing roof lantern?
Often, if the lantern itself is sound. We lift it, rebuild the kerb, dress the new membrane up the upstand and refit the lantern.
Can a sedum roof go on my extension?
Possibly, if the structure can carry the extra weight and the roof has suitable falls and drainage. We check the joists at survey before recommending it.
Do I need my neighbour's permission to replace an extension roof?
Not for a like-for-like re-cover in most cases. The Party Wall Act in England and Wales can apply if the work raises or cuts into a shared wall, so we flag that at survey.
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