Stevenage at a glance
- Postcode districts
- SG1, SG2
- Population
- about 91,774 (GeoNames)
- Council area
- Stevenage Borough Council
- Building approval
- Stevenage Borough Council building control, or a registered building control approver
- Nearest main town
- Luton, about 9 miles
- Guide price region
- East of England (+5% on West Midlands rates)
What makes a good extension roof in Stevenage?
Condensation drives some replacements in Stevenage. Older extension roofs were often built cold, with insulation between the joists and no reliable vapour control. Warm air from the kitchen reaches the cold deck, moisture builds up and the timber suffers. A warm roof deals with the cause, not just the stain.
In a large town like Stevenage, flat roofs are commonly found on lock-up garage blocks on estates or low-rise post-war blocks of flats. 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.
How much does a new extension roof cost in Stevenage?
For Stevenage we use East of England rates: £2,950–£5,150 is the guide for a 20 m² extension roof in EPDM with a new deck and insulation, VAT included. 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 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.
What's included?
- Building control handled where needed, and a written workmanship guarantee
- New abutment upstand and flashing, plus rebuilt rooflight kerbs
- Falls set away from the house wall
- Staged strip-out so the room stays weathertight
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?
- Hitchin · 5 mi
- Letchworth Garden City · 5 mi
- Welwyn Garden City · 7 mi
- Harpenden · 9 mi
- Hertford · 9 mi
- Luton · 9 mi
Extension and kitchen roofs in Stevenage: questions
Do you cover Stevenage?
Yes. Stevenage is part of our Hertfordshire coverage, including postcode districts SG1, SG2. 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 Stevenage?
Where the work needs approval it goes to Stevenage 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 new extension roof cost in Stevenage?
£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.
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.
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.