Cambridge Roofers carries out flat roof installations and repairs in Fulbourn, helping homeowners choose the right material and specification for their extension, garage, or outbuilding.
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The material your flat roof is made from matters more than most people realise. A poorly chosen system on an otherwise well-built roof will fail early. A good material on a poorly prepared deck will do the same. This page covers the main systems available for homes in Fulbourn and the surrounding area, with honest detail about what each one offers and where its limits lie, so you can make an informed decision before spending anything.
For domestic flat roofs in Fulbourn, we work with two systems: EPDM rubber membrane and torch-on modified bitumen felt. Each has a different cost profile, different installation method, and different maintenance characteristics. Neither is universally superior - the right choice depends on your roof.
EPDM stands for ethylene propylene diene monomer. It is a synthetic rubber membrane, typically 1.14mm to 1.5mm thick, bonded to the roof deck with a contact adhesive and supplied in sheets large enough to cover most domestic roofs with few or no seams. Seams are the most common point of failure on any flat roof, so reducing their number is a genuine benefit.
EPDM remains flexible at low temperatures. It does not become brittle or crack in frost. The surface does not degrade under UV radiation, so it maintains its properties without regular surface treatment. Correctly installed, EPDM flat roofs regularly last 25 years or more before any significant remedial work is needed.
Honest pros of EPDM:
Honest cons of EPDM:
Torch-on felt, also called built-up roofing, uses polyester-reinforced bitumen sheets that are melted onto the deck and each other using a gas torch. A proper installation uses at least two layers: a base layer bonded to the deck and a cap sheet torched on top. The mineral surface of the cap sheet reflects some UV and adds mechanical protection.
This is a well-established system with a long track record. Many felt roofs installed in the 1990s are still performing, though most are now approaching the end of their serviceable life. Torch-on felt is a practical choice where the budget is tighter or where the roof geometry makes large EPDM sheets harder to handle.
Honest pros of torch-on felt:
Honest cons of torch-on felt:
The insulation position is as important as the membrane material. In a warm roof, the insulation sits on top of the structural deck and below the membrane. This keeps the deck at room temperature, preventing condensation within the roof build-up. In a cold roof, insulation sits between the joists below the deck, and a ventilation gap must be maintained above the insulation to carry away any condensation. Cold roofs were common in older construction and are more prone to problems if the ventilation path is blocked or inadequate.
For any new installation or full replacement in Fulbourn, a warm roof build-up is generally the better specification. It costs more in materials but performs reliably without the condensation risks associated with cold deck construction.
No membrane system will perform as it should on a damaged or deflecting deck. Before any new membrane goes down, the deck needs to be inspected for soft spots, rot, deflection between joists, and inadequate falls. Flat roofs should have a minimum fall of 1 in 80 - about 12mm per metre - to drain properly. If the existing deck does not achieve this, the fall needs to be corrected with tapered insulation or deck adapters before the membrane is laid.
This is important to understand when comparing quotes. A price that includes stripping the existing surface, checking and repairing the deck, correcting the falls, fitting new outlets, and laying a full new membrane system is a fundamentally different job from one that overlays a new felt on an existing surface. Overlaying is rarely a sound long-term decision because it traps moisture between the layers and hides ongoing deck deterioration.
Any flat roof installation is also an opportunity to improve the rooflight and drainage specification. Modern flat rooflights are double or triple-glazed, offer substantially better thermal performance than older single-glazed units, and can be fitted flush with the membrane so they do not create a dam for rainwater. Drainage outlets and overflows should be checked as part of any re-covering job. An outlet that sits too high above the deck surface will always cause ponding, however good the membrane.
Flat roof installation in and around Fulbourn typically costs between £70 and £120 per square metre for a full strip and relay, depending on the system and the specification of the insulation and deck. A garage roof of around 15 to 20 square metres would normally cost £1,200 to £2,200 installed. A rear extension of 30 square metres might run from £2,500 to £4,000 depending on the build-up chosen and the condition of the existing deck.
EPDM will sit at the higher end of any range; torch-on felt at the lower to middle. The gap is narrower than many people expect once you account for service life - a system that lasts 25 years rather than 15 to 20 years represents better value over the ownership of the property even if the upfront cost is 15 to 20 per cent higher.
Before agreeing to any flat roof work in Fulbourn, ask the roofer to confirm what fall will be achieved after the installation, how the insulation is being positioned (above or below the deck), what the upstand height at walls and parapets will be, and whether the existing deck will be fully inspected and any rotten or deflected sections replaced before the new membrane goes down. The answers to those four questions will tell you a lot about the quality of the work being proposed.
We cover Fulbourn and nearby Cambridge for flat roof surveys and installations. Call us to discuss your roof and we will give you a straight assessment of which system suits it and why.
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Call any time. Calls are answered day and night and passed straight to our roofers.
