Green and sedum roofs across Derbyshire

Guide price

£4,300–£7,900

Survey

Free for new and replacement roofs

Quote

Fixed, in writing

Coverage

England, Wales, Scotland, NI

How much does a green roof cost in Derbyshire?

Guide prices including VAT at East Midlands rates. The fixed price comes after a free survey for new and replacement roofs.

Which flat roofs are common in Derbyshire?

Flat roofs in Derbyshire sit on newer estates where the first extension roofs are now being replaced, shops with flat-roofed rear stores below flats and 1930s semis with flat-roofed garages and kitchen extensions. 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 Derbyshire the application goes to Derby City Council, Chesterfield Borough Council, Erewash Borough Council and 4 other councils. More on the rules.

Can my flat roof take the weight of a green roof?

Not every roof can, which is why we check the structure before quoting. A sedum roof is light compared with an intensive garden, but its growing medium holds water, and a saturated build-up adds significant weight to the roof.

We look at the joist sizes, spans and spacing, the condition of the deck and what the roof sits on. On a recently built extension with generously sized joists, an extensive green roof may be straightforward. On an older garage or a roof with undersized or rotten timbers, the structure may need strengthening, or a structural engineer's calculation may be needed before we can go ahead.

In England, a new roof covering that adds 15% or more to the weight of the roof triggers building control approval, and a green roof will often fall into that category. We handle building control where it is needed. The building regulations page covers the approval routes in each nation.

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.

Which towns in Derbyshire do we cover?

• Derby
• Chesterfield
• Long Eaton
• Ilkeston
• Swadlincote
• Staveley
• Belper
• Heanor
• Alfreton
• Dronfield
• Ripley
• Buxton
• New Mills
• Glossop
• Sinfin

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