Derry/Londonderry at a glance
- Postcode districts
- BT48
- Population
- about 87,153 (GeoNames)
- Council area
- Derry City and Strabane District Council
- Building approval
- Derry City and Strabane District Council building control
- Guide price region
- Northern Ireland (−12% on West Midlands rates)
Why choose a green roof in Derry/Londonderry?
Small commercial buildings and blocks in Derry/Londonderry with a flat roof sometimes add an extensive green roof as part of a refurbishment. The structural check and safe access for maintenance matter even more on these larger roofs, which may need edge protection or fall-arrest points for each visit.
In and around Derry/Londonderry, flat roofs are typically found on newer estates where the first extension roofs are now being replaced, and on terraced streets with flat-roofed rear kitchens and bathrooms. Northern Ireland averages roughly 1,150 mm of rain a year, spread over many wet days, so a roof that sheds water quickly to clear outlets lasts far longer than one that holds puddles.
How much does a green roof cost in Derry/Londonderry?
At Northern Ireland guide rates, a 20 m² insulated extension roof finished as a sedum green roof comes to £3,900–£7,100 including VAT. 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 | £3,900–£7,100 |
| Extension (20 m²), EPDM, new deck + insulation | £2,450–£4,300 |
How is a green roof built on top of a flat roof?
From the bottom up, a green roof is a deck, a waterproofing system with root protection, then drainage, filter, growing medium and plants. The waterproofing does the job of keeping water out. The green layers sit above it.
- Warm roof build-up: vapour control layer, insulation and waterproof membrane on the deck, then the green layers on top. This is the usual choice on a home extension being re-roofed.
- Inverted build-up: waterproofing on the deck, then insulation boards designed to sit above it, then the green layers. This is common on terraces and some commercial roofs.
- Root barrier: roots will exploit any weakness, so the membrane needs to be root-resistant. Some membranes are tested as root-resistant; others need a separate root barrier laid on top.
- Drainage and edges: a drainage layer carries surplus water to outlets, and a gravel or pebble strip is usually left around edges, outlets, upstands and rooflights to keep them clear and accessible.
Upstands still need to rise around 150 mm above the finished surface, which on a green roof means above the top of the growing medium. We check that at the survey, alongside the external fire performance of the build-up where the roof is close to a boundary.
What's included?
- Gravel strips kept clear around edges and outlets
- Structural check of joists, deck and supports
- Pre-grown sedum blankets laid and watered in
- Drainage layer, filter and lightweight growing medium
Building control in Northern Ireland
In Northern Ireland, Technical Booklet F1 sets roof insulation at 0.18 W/m²K when a roof over a heated room is renovated or newly built, where that's feasible. The district council's building control should be contacted before work starts, and we prepare the details it asks for. More on the rules.
Which nearby areas do we also cover?
Green and sedum roofs in Derry/Londonderry: questions
Do you cover Derry/Londonderry?
Yes. Derry/Londonderry is part of our County Londonderry coverage, including postcode districts BT48. 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 Derry/Londonderry?
Where the work needs approval it goes to Derry City and Strabane District Council building control. 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 Derry/Londonderry?
£3,900–£7,100 for a 20 m² insulated extension roof finished as a sedum green roof, at Northern Ireland 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.