Ferndown at a glance
- Postcode districts
- BH22
- Population
- about 17,650 (GeoNames)
- Council area
- Dorset Council
- Building approval
- Dorset Council building control, or a registered building control approver
- Nearest main town
- Bournemouth, about 6 miles
- Guide price region
- South West (+3% on West Midlands rates)
Why choose a green roof in Ferndown?
Garden rooms and outbuildings in Ferndown, 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 Ferndown, flat roofs are common on 1960s and 1970s link-detached houses with flat-roofed garages and porches and on low-rise post-war blocks of flats. 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 Ferndown?
At South West guide rates, a 20 m² insulated extension roof finished as a sedum green roof comes to £4,550–£8,350 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 | £4,550–£8,350 |
| Extension (20 m²), EPDM, new deck + insulation | £2,900–£5,050 |
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?
- Warm or inverted build-up to suit the roof
- Pre-grown sedum blankets laid and watered in
- Structural check of joists, deck and supports
- Root-resistant membrane or separate root barrier
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?
- Wimborne Minster · 4 mi
- Bournemouth · 6 mi
- Christchurch · 7 mi
- Poole · 7 mi
- New Milton · 11 mi
- Salisbury · 19 mi
Green and sedum roofs in Ferndown: questions
Do you cover Ferndown?
Yes. Ferndown is part of our Dorset coverage, including postcode districts BH22. 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 Ferndown?
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 Ferndown?
£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.
Does a green roof leak more than a normal flat roof?
No, as long as it is built correctly. The waterproofing beneath is what keeps water out, and the green layers protect it from sun and weather. The main risk is building it on a weak or ageing membrane.
What happens if a green roof needs repairing?
The green layers are lifted around the problem area, the membrane is repaired, and the layers are relaid. Building on a sound, long-life membrane in the first place keeps that to a minimum.