Fakenham Roofers installs and repairs flat roofs on extensions, garages, and outbuildings in Burnham Market, and this page gives you an honest picture of what the work costs and why prices vary.
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Two flat roofs of the same physical size can cost very different amounts to replace. The membrane area is only one part of the calculation. Deck condition, access, drainage work, the number of upstands, and the system being installed all push the final figure up or down. This page sets out typical current UK price ranges and explains the main factors so you can assess any quote you receive.
These are realistic working figures based on what flat roofing jobs typically cost in the UK at the time of writing. Every job is different, and a survey is the only way to get an accurate price for your specific roof.
As a starting point, flat roof replacement in the UK currently costs in the following ranges:
These figures assume a sound, level deck and straightforward access. Each of the factors below can move the final cost outside these ranges.
The single biggest variable in a flat roof replacement quote is what the deck looks like once the old membrane comes off. If the plywood or OSB boarding underneath is dry and sound, the roofer can work directly on top of it. If boards are wet, soft, or rotten, they need to come out and be replaced with new exterior-grade plywood.
Replacing decking adds cost for both materials and time. Pricing is typically per sheet of plywood, usually 18mm exterior grade. A sheet covers roughly 2.4 x 1.2 metres - about 2.9 square metres. If half the deck on a 25-square-metre roof needs replacing, that is around four to five sheets plus fitting time. It sounds modest but adds meaningfully to the overall price.
This is why any reputable roofer will either survey the deck properly before quoting, or set out clearly in writing how additional decking will be priced if it is found to be needed. A quote that makes no mention of what happens if the deck is rotten is incomplete.
EPDM rubber membrane costs more than torch-on mineral felt, both in materials and in labour. The EPDM membrane itself is a more expensive product, and the bonding process takes more time per square metre than torching on felt. However, EPDM has a longer expected service life. Manufacturers typically rate EPDM systems at 20 years or more, whereas a standard torch-on felt system is generally expected to last 10-20 years, depending on product quality and installation.
Looked at over the life of the roof, EPDM often works out as better value even though the upfront cost is higher. On a tight budget where the aim is to make a roof serviceable for the next 5-10 years, a well-installed felt system may be the more practical choice. The right answer depends on your circumstances and what you want the roof to do for you.
A ground-floor rear extension roof that a roofer can reach from a step ladder alongside the property is the easiest access scenario. Cost stays within the base range. A flat roof above a first-floor addition, or one where scaffolding is needed to work safely at height, adds a day of scaffolding erection and hire to the overall cost. Scaffold hire and erection for a typical residential job adds roughly £400-£900 depending on scale and duration.
Access is also relevant to how waste is removed. If old felt, decking and insulation can be thrown directly into a skip positioned next to the building, removal is quick. If the route to a skip requires carrying material through the house or over other parts of the roof, it takes longer.
A flat roof with correct fall and a working outlet in good condition can be re-roofed without significant drainage work. But if the fall is inadequate, or if there is ponding water that has been a persistent problem, addressing the drainage adds cost.
Installing tapered insulation boards to create a proper fall across a roof that was originally built with insufficient slope is an effective but more expensive solution. Tapered insulation is cut to a wedge profile so that water is directed towards the outlet. On a 20-square-metre roof this might add £400-£800 to the job, depending on the degree of fall needed. It is, however, a genuine long-term fix - without it, a new membrane on a badly falling roof will degrade faster than it should.
Replacing or upgrading a drainage outlet adds a relatively modest cost individually, but if the outlet needs to be moved to a more effective position, or if new internal pipework is involved, the figure rises.
Every point where the flat roof membrane meets a wall, parapet, chimney or other upstand requires additional work. The membrane must be turned up to a minimum of 150mm against the wall and sealed with termination bar and compatible sealant. Complex roof shapes with multiple internal corners, chimney stacks, skylights or rooflights mean more edge detailing, and more detailing means more time.
A simple rectangular garage roof with a single gutter edge has very little detailing. A rear extension that runs up against three walls, includes a rooflight, and has a parapet on one side has considerably more. This is reflected in any accurate quote.
If you want a new or replacement rooflight fitted as part of the job, this adds to the cost. A basic flat rooflight supplied and installed typically adds £300-£700 depending on size and specification. Rooflights need to be properly upstand-flashed into the membrane - a poorly detailed rooflight is one of the most reliable ways to get a leak on an otherwise well-installed flat roof.
A repair - patching a failed seam, re-bonding a lifted edge, or replacing a small area of membrane - costs far less than replacement. Minor repairs might be in the region of £150-£400 depending on what is involved. But a repair only makes economic sense if the rest of the roof is in sound condition and the deck is dry. Patching a roof that is near the end of its life means paying for a repair now and a full replacement a year or two later. In most cases, a roofer will tell you honestly whether repair or replacement makes better sense once the roof has been inspected.
The only way to get a reliable price for your flat roof is to have someone on the roof to look at it properly. Prices quoted over the phone or from photos are not accurate - they cannot account for deck condition, drainage, access, or the specific detailing required. For flat roofing work in Burnham Market or nearby, call us to arrange a survey and we will give you a clear, itemised quote based on what we actually find.
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