Dorchester at a glance
- Postcode districts
- DT1
- Population
- about 16,879 (GeoNames)
- Council area
- Dorset Council
- Building approval
- Dorset Council building control, or a registered building control approver
- Nearest main town
- Poole, about 20 miles
- Guide price region
- South West (+3% on West Midlands rates)
Why choose a green roof in Dorchester?
Garden rooms and outbuildings in Dorchester, as elsewhere, often have small flat roofs that are seen from the house and garden. A sedum finish helps them blend in, provided the structure is strong enough and the roof underneath is built properly.
Around Dorchester, flat roofs are common on bungalows with flat-roofed side extensions and dormers and on 1930s semis with flat-roofed garages and kitchen extensions. 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.
How much does a green roof cost in Dorchester?
Guide price in Dorchester: £4,550–£8,350 for a 20 m² insulated extension roof finished as a sedum green roof, 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 with sedum green roof | £4,550–£8,350 |
| Extension (20 m²), EPDM, new deck + insulation | £2,900–£5,050 |
Can a green roof go on my existing flat roof?
Only if the existing waterproofing is sound, root-resistant or protected by a root barrier, and has plenty of life left. In most cases it makes more sense to lay a green roof as part of a replacement.
Once the sedum, substrate and drainage layers are down, the membrane underneath is hard to inspect and expensive to repair, because the green layers have to be lifted to get to it. Putting a green roof on an ageing covering risks paying for the greenery twice. Our repair or replace guide helps you judge whether your current roof is a sensible base.
As for planning, re-covering a house roof normally needs no application if its appearance doesn't change materially. Because a green roof does change how a roof looks, check with your council, especially for listed buildings, conservation areas and roofs that are easily seen. The planning guide has more.
What's included?
- Warm or inverted build-up to suit the roof
- Pre-grown sedum blankets laid and watered in
- Drainage layer, filter and lightweight growing medium
- Structural check of joists, deck and supports
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?
- Weymouth · 7 mi
- Yeovil · 18 mi
- Poole · 20 mi
- Wimborne Minster · 20 mi
- Ferndown · 24 mi
- Bournemouth · 24 mi
Green and sedum roofs in Dorchester: questions
Do you cover Dorchester?
Yes. Dorchester is part of our Dorset coverage, including postcode districts DT1. 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 Dorchester?
Where the work needs approval it goes to Dorset 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 green roof cost in Dorchester?
£4,550–£8,350 for a 20 m² insulated extension roof finished as a sedum green roof, at South West guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
Can I walk on a green roof?
Only for maintenance, and only where it is safe. Most extensive green roofs on homes aren't designed as roof terraces, and a terrace generally needs planning permission and edge protection.
Can a green roof have a rooflight in it?
Yes. The rooflight sits on a raised upstand with a gravel strip around it, so the planting stays clear of the glazing and the upstand stays visible and dry.