- Guide price
- £2,900–£5,050
- Survey
- Free for new and replacement roofs
- Quote
- Fixed, in writing
- Coverage
- England, Wales, Scotland, NI
Wiltshire at a glance
- Largest towns
- Swindon, Salisbury, Trowbridge, Chippenham
- Postcode areas
- BA, SN, SP
- Building control
- Swindon Borough Council and Wiltshire Council
- Neighbouring areas
- Bristol · Gloucestershire · Somerset · Dorset
- Guide price region
- South West (+3% on West Midlands rates)
How much does a flat roof replacement cost in Wiltshire?
Guide prices including VAT at South 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 | £2,900–£5,050 |
| Single garage (18 m²), torch-on felt | £1,550–£2,700 |
| Extension (20 m²), GRP, new deck + insulation | £3,100–£5,550 |
| Single garage (18 m²), EPDM rubber | £1,650–£2,900 |
Which flat roofs are common in Wiltshire?
Flat roofs in Wiltshire sit on 1930s semis with flat-roofed garages and kitchen extensions, bungalows with flat-roofed side extensions and dormers and low-rise post-war blocks of flats. The South West averages roughly 1,260 mm of rain a year and many roofs face wind off the Atlantic, so we specify fixings and edge details for wind uplift as well as drainage. 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 Wiltshire the application goes to Swindon Borough Council and Wiltshire Council. More on the rules.
Should I overlay my old flat roof or strip it fully?
Strip it fully if the deck is soft, the insulation is wet or the falls are wrong; an overlay only suits a dry, sound roof that already drains well. Covering a wet roof traps the moisture, and rot carries on out of sight.
An overlay also raises the roof level, eating into upstand height at walls and door thresholds, and every layer adds weight. In England, a covering that adds 15% or more to the roof's weight needs building control approval. Signs it is time to replace rather than repair:
- ponding that lingers long after rain
- blisters, cracking or crazing across wide areas
- bare bitumen where the mineral chippings have gone
- split laps and lifted upstands or flashings
- damp ceilings, or a deck that has gone soft
- leaks that return after each repair
A single defect on an otherwise dry roof can usually be put right with a repair. If you're unsure, a survey settles it, and our guides to overlay or strip and repair or replace go further.
Which system should I replace my flat roof with?
The right system depends on the roof's size, shape, use and number of details, so no single material suits every roof. These are the usual starting points:
- EPDM rubber suits simple, rectangular roofs, where one sheet can often cover the area with few or no joins.
- GRP fibreglass suits roofs with many corners, rooflights or edges, and gives a rigid surface for occasional maintenance traffic.
- Torch-on felt is a layered, hard-wearing system that keeps the cost down on larger or plain roofs.
- Liquid-applied systems handle awkward details and can overlay a sound existing surface.
- Single-ply and mastic asphalt are more usual on commercial roofs, blocks and terraces.
We recommend a system at survey and explain why. Our EPDM vs GRP vs felt guide sets out the trade-offs if you want to compare first.
Which towns in Wiltshire do we cover?
Flat roof replacement in Wiltshire: questions
Which towns in Wiltshire do you cover?
All of Wiltshire. 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 flat roof replacement cost in Wiltshire?
£2,900–£5,050 for a 20 m² extension roof in EPDM with a new deck and insulation, at South 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 Wiltshire?
It depends on where the roof is: in Wiltshire that's Swindon Borough Council and Wiltshire Council. 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.
Can you replace just part of a flat roof?
Sometimes, if the rest is sound and dry. Renovating more than half of a roof over a heated room usually brings the whole roof under the insulation rules, so a full replacement can make more sense.
Do I need to be at home while the roof is replaced?
Not for most of the job, as long as the team can reach the roof and there is room for a skip. We ask you to be there at the start to agree the plan and at the end to look over the finished roof.
What guarantees come with a replacement roof?
Every re-roof comes with a written workmanship guarantee, with the length set out in your quote. Manufacturer material guarantees are available on many systems and we register them for you where the system allows; ask about insurance-backed options too.
Everything about flat roof replacement → · All flat roofing in Wiltshire →