Dartford at a glance
- Postcode districts
- DA1
- Population
- about 51,240 (GeoNames)
- Council area
- Dartford Borough Council
- Building approval
- Dartford Borough Council building control, or a registered building control approver
- Nearest main town
- Grays, about 5 miles
- Guide price region
- South East (+10% on West Midlands rates)
What makes a good extension roof in Dartford?
Ponding against the house wall is a common reason for replacing an extension roof in Dartford. When the deck dips near the wall or the fall runs the wrong way, water sits against the abutment and eventually gets in. A new roof with corrected falls moves the water to the gutter.
In a large town like Dartford, flat roofs are commonly found on bungalows with flat-roofed side extensions and dormers or 1930s semis with flat-roofed garages and kitchen extensions. 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.
How much does a new extension roof cost in Dartford?
Guide price in Dartford: £3,100–£5,350 for a 20 m² extension roof in EPDM with a new deck and insulation, including VAT at South 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 | £3,100–£5,350 |
| Extension (20 m²), GRP, new deck + insulation | £3,300–£5,900 |
| Extension (20 m²), EPDM, insulation + 1 rooflight upstand | £3,300–£5,750 |
| Single garage (18 m²), EPDM rubber | £1,750–£3,100 |
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?
- Falls set away from the house wall
- New deck, vapour control layer and warm-roof insulation
- New abutment upstand and flashing, plus rebuilt rooflight kerbs
- Free survey of the roof, abutment and room below
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?
Extension and kitchen roofs in Dartford: questions
Do you cover Dartford?
Yes. Dartford is part of our Kent coverage, including postcode districts DA1. 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 Dartford?
Where the work needs approval it goes to Dartford 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 Dartford?
£3,100–£5,350 for a 20 m² extension roof in EPDM with a new deck and insulation, at South East guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
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.
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.