Lambeth at a glance
- Postcode districts
- SW9, SW2, SW4, SE24, SW8, SW12, SE21, SE27 and 1 more
- Council area
- London Borough of Lambeth
- Building approval
- London Borough of Lambeth building control, or a registered building control approver
- Guide price region
- London (+20% on West Midlands rates)
Why choose a green roof in Lambeth?
If you're replacing an old flat roof in Lambeth, it's worth deciding whether to add sedum at the same time. If the structure can take it, that is the ideal moment, because the waterproofing is new and the green layers won't need lifting for a long time.
Around Lambeth, flat roofs are common on mansard and dormer loft conversions and on shops with flat-roofed stores below flats above. 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 Lambeth?
At London guide rates, a 20 m² insulated extension roof finished as a sedum green roof comes to £5,300–£9,700 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 | £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
- Structural check of joists, deck and supports
- 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?
- Southwark · 2 mi
- Wandsworth · 4 mi
- Westminster · 4 mi
- Lewisham · 4 mi
- Kensington and Chelsea · 4 mi
- Camden · 5 mi
Green and sedum roofs in Lambeth: questions
Do you cover Lambeth?
Yes. Lambeth is part of our London coverage, including postcode districts SW9, SW2, SW4, SE24, SW8, SW12 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 Lambeth?
Where the work needs approval it goes to London Borough of Lambeth 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 Lambeth?
£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 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 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.