Choosing the right flat roofing material for your garage or extension in March makes a bigger difference to long-term performance than most homeowners realise.
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Downham Market Roofers install and repair flat roofs on garages, extensions, outbuildings and smaller commercial properties in and around Downham Market, as well as nearby villages including Southery, Stoke Ferry, Shouldham, Shouldham Thorpe, Stradsett, Swaffham, Watlington, West Acre, West Walton, Walpole, Wormegay and Runcton Holme. We work with EPDM rubber and torch-on felt, and we will point you to the system that suits your property - not simply whichever one is easier for us to source.
Flat roofing has come a long way from the basic single-layer felt that covered most garages and extensions built in the 1970s and 1980s. There are now genuine choices to be made, and the right answer depends on the size of your roof, how it is used, your budget and how long you intend to keep the property.
Torch-on felt - sometimes called built-up roofing or modified bitumen felt - is laid in two or three layers using a gas torch to bond each layer to the one below. The result is a continuous, fully adhered membrane with no loose areas where water can track sideways underneath it.
Modern torch-on felt is far more durable than the old mineral-faced single-layer product it has largely replaced. A properly installed two-layer torch-on system on a flat garage roof can be expected to perform well for 15-20 years. The top layer is usually finished in mineral slate or a reflective surface, which helps the membrane resist UV degradation.
EPDM (ethylene propylene diene monomer) is a single-ply rubber membrane that has been used on commercial and industrial roofs for decades. It has become increasingly popular on domestic garages and extensions over the last 15 years because of its longevity and the fact that it comes in very large single sheets that eliminate most of the seam-related failures seen in felt systems.
A well-installed EPDM roof can realistically be expected to remain watertight for 30-50 years in normal UK conditions. The material is flexible even at very low temperatures, which makes it resistant to the cracking that affects aged bitumen felt in hard winters. It is bonded to the deck using a contact adhesive, and the edges are turned up and secured to timber or metal upstands with purpose-made tape and trim.
Any flat roof replacement is an opportunity to improve the insulation beneath the membrane. Building regulations require a minimum thermal performance for new flat roofs, and if your existing roof has no insulation - which is common on pre-2000 garages - adding rigid foam insulation boards when the membrane is replaced adds very little to the overall cost of the project.
There are two configurations: warm deck (insulation above the deck, below the membrane) and cold deck (insulation between the joists, below the deck). Warm deck construction is the current standard for new and replacement flat roofs. It eliminates the risk of condensation forming within the roof structure and gives more predictable long-term performance.
As a general guide: if your roof is a straightforward rectangle on a garage or a simple extension and you want the longest possible life with the least future maintenance, EPDM is the better choice. If your budget is tighter and the roof area is modest, a well-installed torch-on felt system will serve you well for 15 or more years.
The condition and quality of the existing deck also matters. If the deck boards are sound and level, either system can go straight over them. If the deck needs replacing - because of rot or inadequate falls - the additional cost of re-decking is the same regardless of which membrane you choose, so it is often worth spending a little more on the membrane when you are already spending on the deck.
We will discuss both options with you, explain what we can see on your roof and give you a clear picture of what each system will cost. The decision is yours to make, and we will not push you toward the pricier option if the cheaper one is genuinely suitable.
Whether you have an old felt roof on a garage, a leaking extension roof or a commercial outbuilding that needs a full replacement, call Downham Market Roofers to arrange a survey. We cover March and all the surrounding villages, and we will give you an honest assessment of your options before any work is agreed.
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Call any time. Calls are answered day and night and passed straight to our roofers.
