Chelmsford at a glance
- Postcode districts
- CM1
- Population
- about 111,511 (GeoNames)
- Council area
- Chelmsford City Council
- Building approval
- Chelmsford City Council building control, or a registered building control approver
- Nearest main town
- Basildon, about 12 miles
- Guide price region
- East of England (+5% on West Midlands rates)
Why choose a green roof in Chelmsford?
Garden rooms and outbuildings in Chelmsford, 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.
In and around Chelmsford, flat roofs are typically found on 1930s semis with flat-roofed garages and kitchen extensions, and on bungalows with flat-roofed side extensions and dormers. The East of England is the driest part of Britain, with parts of the Anglian region around 630 mm a year, so summer heat and UV, not rainfall, do most of the ageing on a felt roof.
How much does a green roof cost in Chelmsford?
At East of England guide rates, a 20 m² insulated extension roof finished as a sedum green roof comes to £4,650–£8,500 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 | £4,650–£8,500 |
| Extension (20 m²), EPDM, new deck + insulation | £2,950–£5,150 |
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?
- Structural check of joists, deck and supports
- Gravel strips kept clear around edges and outlets
- Drainage layer, filter and lightweight growing medium
- Pre-grown sedum blankets laid and watered in
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?
Green and sedum roofs in Chelmsford: questions
Do you cover Chelmsford?
Yes. Chelmsford is part of our Essex coverage, including postcode districts CM1. 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 Chelmsford?
Where the work needs approval it goes to Chelmsford City 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 Chelmsford?
£4,650–£8,500 for a 20 m² insulated extension roof finished as a sedum green roof, at East of England guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
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.
Can you put a sedum roof on a garage?
Often, yes, if the structure is strong enough. Many older garage roofs have light timbers, so a structural check comes first and strengthening may be needed.