Bexley at a glance
- Postcode districts
- DA6, DA7, DA5, DA8, DA16, DA17, DA15, DA18 and 1 more
- Council area
- London Borough of Bexley
- Building approval
- London Borough of Bexley building control, or a registered building control approver
- Guide price region
- London (+20% on West Midlands rates)
Why choose a green roof in Bexley?
Garden rooms and outbuildings in Bexley, 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.
Bexley's flat roofs are mostly on mansion blocks and purpose-built flats with large flat roofs, with plenty on kitchen extensions and roof terraces behind period houses too. The Thames basin is one of the drier parts of Britain at roughly 730 mm of rain a year, but summer heat is the bigger test here: dark membranes on south-facing roofs swing a long way in temperature.
How much does a green roof cost in Bexley?
For Bexley we use London rates: £5,300–£9,700 is the guide for a 20 m² insulated extension roof finished as a sedum green roof, VAT included. 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 | £5,300–£9,700 |
| Extension (20 m²), EPDM, new deck + insulation | £3,350–£5,850 |
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.
What's included?
- Root-resistant membrane or separate root barrier
- Warm or inverted build-up to suit the roof
- Drainage layer, filter and lightweight growing medium
- Gravel strips kept clear around edges and outlets
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 Bexley: questions
Do you cover Bexley?
Yes. Bexley is part of our London coverage, including postcode districts DA6, DA7, DA5, DA8, DA16, DA17 and 3 more. 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 Bexley?
Where the work needs approval it goes to London Borough of Bexley 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 Bexley?
£5,300–£9,700 for a 20 m² insulated extension roof finished as a sedum green roof, at London guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
Can you put a green roof on a pitched roof?
We install green roofs on flat roofs only. Sloping green roofs need extra restraint to stop the growing medium slipping, and they are a specialist job outside our work.
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.