- Guide price
- £2,600–£4,550
- Survey
- Free for new and replacement roofs
- Quote
- Fixed, in writing
- Coverage
- England, Wales, Scotland, NI
Northumberland at a glance
- Largest towns
- Blyth, Cramlington, Ashington, Bedlington
- Postcode areas
- NE
- Building control
- Northumberland County Council
- Neighbouring areas
- Tyne and Wear · County Durham · North Yorkshire · Cumbria
- Guide price region
- North East (−7% on West Midlands rates)
How much does a new extension roof cost in Northumberland?
Guide prices including VAT at North 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 | £2,600–£4,550 |
| Extension (20 m²), GRP, new deck + insulation | £2,800–£5,000 |
| Extension (20 m²), EPDM, insulation + 1 rooflight upstand | £2,800–£4,850 |
| Single garage (18 m²), EPDM rubber | £1,500–£2,600 |
Which flat roofs are common in Northumberland?
Flat roofs in Northumberland sit on bungalows with flat-roofed side extensions and dormers, terraced streets with flat-roofed rear kitchens and bathrooms and newer estates where the first extension roofs are now being replaced. England averages roughly 870 mm of rain a year; the North East is drier than the west but cold and windy near the coast, so wind uplift and freeze-thaw are in the specification. 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 Northumberland the application goes to Northumberland County Council. 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 Northumberland do we cover?
Extension and kitchen roofs in Northumberland: questions
Which towns in Northumberland do you cover?
All of Northumberland. 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 Northumberland?
£2,600–£4,550 for a 20 m² extension roof in EPDM with a new deck and insulation, at North East guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
Which postcode areas do you cover in Northumberland?
All of Northumberland, including the NE 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.
Will a new extension roof sit higher than the old one?
Usually, by the thickness of the added insulation. We check the height against the upstairs window sills, door thresholds and wall flashings at survey so everything still works.
How do I know my extension roof needs replacing rather than repairing?
Repeated leaks, a soft deck, wet insulation or widespread cracking point to replacement. A single defect on a dry, sound roof can usually be repaired.
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