A green roof starts with the waterproofing underneath it. We design and install extensive, biodiverse and blue roof build-ups over single ply, bituminous and hot melt systems with root resistant membranes, so the roof delivers biodiversity net gain and attenuation for planning and still carries a full manufacturer guarantee.
The membrane under a green roof has to be root resistant, fully guaranteed and tested before anything goes on top of it, because once the substrate is down nobody is lifting it to find a leak. We flood test or electronically test the waterproofing and have the manufacturer sign it off before the build-up starts.
Lightweight extensive build-ups with sedum blanket or wildflower substrate suit most existing structures and need little maintenance. They are the usual route to biodiversity net gain on a commercial refurbishment and can be installed over a warm roof or an inverted roof.
Where a planning condition asks for a biodiverse roof, the substrate depth, seed mix and habitat features such as log piles and sand patches are specified to the ecologist report. We work with the landscape designer and the membrane manufacturer so the build-up stays inside the guarantee.
Blue roof attenuation layers hold rainfall on the roof and release it slowly, taking load off the drainage and often removing the need for an underground tank. Combined with a green roof on top, it is one of the more useful things a flat roof can do for a planning application.
That depends on the structure and the waterproofing. An extensive sedum build-up saturated weighs roughly 80 to 150 kg per square metre, which many commercial decks can take, but the existing waterproofing is rarely root resistant or young enough to bury. Normally the roof is re-waterproofed at the same time. A structural check and our survey come first.
Green roofs do not leak; bad waterproofing under them does. That is why the membrane is root resistant, electronically tested and signed off by the manufacturer before the build-up goes on, and why we would rather re-waterproof than bury a roof we cannot guarantee.
An extensive roof needs two visits a year to clear outlets, remove unwanted plants and check the edges. We offer a maintenance schedule alongside the guarantee so the roof stays compliant and the guarantee stays valid.
Often. Biodiversity net gain, urban greening factor and sustainable drainage conditions can all be addressed with the right build-up, and a blue roof can replace a below ground attenuation tank. We produce the build-up specification and the attenuation calculation with the manufacturer for the planning submission.
Root resistant grades of single ply, bituminous cap sheets with a root barrier and hot melt systems on inverted roofs. All the manufacturers we work with, including Bauder, IKO and Sika, offer certified green roof systems with a single guarantee covering the waterproofing and the build-up.
Nationwide, with the survey and the site team coming from whichever office is closer. Pick your division and the phone numbers on this page follow.
Covering the West and East Midlands, the South, the South West, East Anglia and the home counties from Jubilee Estate, Gorsey Lane, Coleshill.
The Midlands divisionCovering the North West, the North East, Yorkshire, Cumbria and Scotland from Riverside, Mountbatten Way, Congleton.
The North divisionSend us the outline or the tender documents and a surveyor will come back to you, normally the same working day. The survey and report are free.
Send Absolute Waterproofing your roofing enquiry or tender. Give us the outline below and one of our surveyors will come back to you, usually the same working day.