Green and sedum roofs in Milton Keynes

Why choose a green roof in Milton Keynes?

Garden rooms and outbuildings in Milton Keynes, 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 a city like Milton Keynes, flat roofs are commonly found on bungalows with flat-roofed side extensions and dormers or low-rise post-war blocks of flats. Much of the South East sits in the drier Thames catchment at roughly 730 mm of rain a year, so the usual failures are at joints, upstands and outlets rather than from sheer volume of rain.

How much does a green roof cost in Milton Keynes?

At South East guide rates, a 20 m² insulated extension roof finished as a sedum green roof comes to £4,850–£8,900 including VAT. The fixed price comes after a free survey for new and replacement roofs.

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
• Gravel strips kept clear around edges and outlets
• Structural check of joists, deck and supports

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?

• Newport Pagnell · 3 mi
• Bletchley · 3 mi
• Leighton Buzzard · 10 mi
• Ampthill · 11 mi
• Kempston · 12 mi
• Bedford · 14 mi

Other flat roof work in Milton Keynes

• Emergency leak repairs
• Balconies and roof terraces
• Extension and kitchen roofs
• Commercial flat roofing
• Single-ply membrane roofing
• Flat roof repairs
• All services in Milton Keynes