- Guide price
- £2,650–£4,650
- Survey
- Free for new and replacement roofs
- Quote
- Fixed, in writing
- Coverage
- England, Wales, Scotland, NI
Greater Manchester at a glance
- Largest towns
- Manchester, Oldham, Wigan, Bolton
- Postcode areas
- BL, M, OL, SK, WA, WN
- Building control
- Manchester City Council, Oldham Council, Wigan Council and 7 other councils
- Neighbouring areas
- Cheshire · Lancashire · Merseyside · West Yorkshire
- Guide price region
- North West (−5% on West Midlands rates)
How much does a new extension roof cost in Greater Manchester?
Guide prices including VAT at North West 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 | £2,650–£4,650 |
| Extension (20 m²), GRP, new deck + insulation | £2,850–£5,100 |
| Extension (20 m²), EPDM, insulation + 1 rooflight upstand | £2,850–£4,950 |
| Single garage (18 m²), EPDM rubber | £1,500–£2,650 |
Which flat roofs are common in Greater Manchester?
Flat roofs in Greater Manchester sit on low-rise post-war blocks of flats, 1930s semis with flat-roofed garages and kitchen extensions and 1960s and 1970s link-detached houses with flat-roofed garages and porches. The North West is one of England's wetter regions, averaging roughly 1,290 mm of rain a year, so falls, outlets and well-detailed upstands matter more than the membrane colour. 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 Greater Manchester the application goes to Manchester City Council, Oldham Council, Wigan Council and 7 other councils. More on the rules.
Which flat roof system suits a kitchen extension?
On a plain rectangular extension, EPDM rubber is a strong, quiet choice that can often be laid in one sheet. It handles the slight movement between an extension and the house well.
Where the roof has a lantern, several rooflights or an internal corner, GRP fibreglass forms neat, rigid details around each one. Torch-on felt is a proven layered system and keeps costs down, though near timber cladding or at fragile junctions we may prefer a cold-applied method. If the extension is overlooked from upstairs windows, a sedum green roof is worth considering, provided the structure can take the extra load.
Whatever the membrane, the insulation sits above the deck as a warm roof. Our warm vs cold roof guide explains why.
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.
Which towns in Greater Manchester do we cover?
- Manchester
- Oldham
- Wigan
- Bolton
- Stockport
- Salford
- Rochdale
- Sale
- Bury
- Altrincham
- Middleton
- Ashton-under-Lyne
- Leigh
- Stretford
- Urmston
- Eccles
- Tyldesley
- Hyde
- Walkden
- Prestwich
- Radcliffe
- Cheadle Hulme
- Heywood
- Denton
- Stalybridge
- Ashton in Makerfield
- Westhoughton
- Farnworth
- Saddleworth
- Hindley
- Golborne
- Droylsden
- Royton
- Failsworth
- Hazel Grove
- Irlam
- Horwich
- Bramhall
- Ramsbottom
- Bredbury
- Longsight
Extension and kitchen roofs in Greater Manchester: questions
Which towns in Greater Manchester do you cover?
All of Greater Manchester. 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 Greater Manchester?
£2,650–£4,650 for a 20 m² extension roof in EPDM with a new deck and insulation, at North West guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
Which council handles building control for a flat roof in Greater Manchester?
It depends on where the roof is: in Greater Manchester that's Manchester City Council, Oldham Council, Wigan Council and 7 other councils. 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. We confirm which applies at the survey.
Why does my extension ceiling get damp in winter if the roof isn't leaking?
That is often condensation in a cold roof, where warm, moist air reaches the cold underside of the deck. A warm-roof replacement with a vapour control layer usually solves it.
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.
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.
Everything about extension and kitchen roofs → · All flat roofing in Greater Manchester →