- Guide price
- £750–£1,250
- Survey
- Free for new and replacement roofs
- Quote
- Fixed, in writing
- Coverage
- England, Wales, Scotland, NI
Northamptonshire at a glance
- Largest towns
- Northampton, Corby, Kettering, Wellingborough
- Postcode areas
- NN
- Building control
- West Northamptonshire Council and North Northamptonshire Council
- Neighbouring areas
- Leicestershire · Bedfordshire · Warwickshire · Cambridgeshire
- Guide price region
- East Midlands (−2% on West Midlands rates)
How much does a porch or bay roof cost in Northamptonshire?
Guide prices including VAT at East Midlands rates. The fixed price comes after a free survey for new and replacement roofs.
| Job | Guide price inc VAT |
|---|---|
| Porch or bay (4 m²), EPDM | £750–£1,250 |
| Single garage (18 m²), EPDM rubber | £1,550–£2,750 |
| Extension (20 m²), GRP, new deck + insulation | £2,950–£5,300 |
Which flat roofs are common in Northamptonshire?
Flat roofs in Northamptonshire sit on bungalows with flat-roofed side extensions and dormers, 1960s and 1970s link-detached houses with flat-roofed garages and porches and terraced streets with flat-roofed rear kitchens and bathrooms. The East Midlands is drier than the west of Britain, so most flat roofs here fail through age, UV and poor detailing at upstands rather than sheer rainfall. 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 Northamptonshire the application goes to West Northamptonshire Council and North Northamptonshire Council. More on the rules.
Do I need permission to re-roof a porch or bay?
Usually not. Re-covering a porch or bay roof without materially changing how it looks does not normally need planning permission, and an unheated open porch is not usually a thermal element.
The picture changes if the bay or porch is part of a heated room: replacing most of the roof can then bring it under the insulation rules for renovated roofs, which may need building control approval in England, a check in Wales, building standards in Scotland or district council building control in Northern Ireland. On a very small roof, adding insulation may not be technically feasible because of the height available below the window sill above. We assess that at survey.
Listed buildings need consent for changes that affect their character, and conservation areas can restrict changes to the front of a house. See our building regulations page for more detail.
Which material looks best on a porch or bay roof?
For most porches, EPDM rubber gives a neat, dark grey finish that sits quietly on the front of a house, and on a small roof it can usually be laid as one piece. For angled bays and curved canopies, GRP fibreglass or a liquid-applied system follows the shape without folds or joins.
Many older bay windows and porches were finished in lead, which has a distinctive look. Where you want to keep that appearance, especially on a period house, we can discuss a lead-look finish or retaining lead flashings at the wall. On a listed building or in a conservation area, changing from lead to a membrane may need consent, so we check that at survey.
Colour matters more here than on a hidden rear roof. GRP topcoats come in several colours, and EPDM is typically black or dark grey.
Which towns in Northamptonshire do we cover?
Porch, bay and canopy roofs in Northamptonshire: questions
Which towns in Northamptonshire do you cover?
All of Northamptonshire. 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 porch or bay roof cost in Northamptonshire?
£750–£1,250 for a small 4 m² porch or bay roof in EPDM, at East Midlands 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 Northamptonshire?
It depends on where the roof is: in Northamptonshire that's West Northamptonshire Council and North Northamptonshire 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.
Why is my porch roof leaking when the felt looks fine?
The water is often coming from the wall junction, not the roof surface. A failed flashing, cracked mortar or porous brick above can let water in behind the upstand.
Should I replace lead on my bay roof with EPDM or GRP?
It depends on the house and your priorities. Membranes usually cost less and have no scrap value to thieves, but on a period or listed property keeping a lead appearance may matter or be required.
How long will a new porch roof last?
With good specification and maintenance, EPDM is indicatively 25–50 years and GRP 20–40.
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