Cambridge Roofers installs and repairs flat roofs for homeowners in Little Shelford, covering extensions, garages, and outbuildings with EPDM rubber and torch-on felt systems.
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A flat roof is not truly flat - it needs a slight fall, typically a minimum of 1:80 gradient, to drain water away from the surface. When that fall is missing or has settled out over the years, water sits on the membrane and works its way into any weak point. A proper installation starts by checking the deck structure, correcting the fall if needed, and only then laying the membrane.
Two common systems for flat roofs are EPDM rubber and torch-on felt. EPDM is a single-ply rubber membrane bonded or mechanically fixed to the deck. It handles movement well, resists frost and UV, and a correctly installed EPDM roof can last 25 years or more. Torch-on felt uses layers of bitumen-based sheet, heat-welded together and to the upstands. It is a proven system that has been used on UK homes for decades and suits many garage and extension roofs well.
Flat roofing in Cambridge and nearby villages typically costs between £70 and £120 per square metre for a standard EPDM installation, depending on deck condition, access, and any fall correction required. Torch-on felt tends to sit at the lower end of that range. A single-garage roof of around 15 square metres might cost £1,200 to £2,000 fully installed. A larger extension roof of 40 square metres could be £3,000 to £5,000 or more once detailing and upstands are included.
These are honest ballpark figures. The only way to get an accurate number is a proper survey, because deck condition varies enormously - a soft or rotted deck board adds cost that no one can quote around without seeing it.
This is the part most homeowners skip, and it is where problems begin. Choosing on price alone is the single biggest mistake you can make with flat roofing. A cheap installation that fails in three years costs far more in water damage and re-roofing than a properly priced job done right first time.
Here are the questions worth asking any contractor before you agree to the work.
A knowledgeable roofer will explain the choice. If the answer is simply "we always use EPDM" or "we always use felt" without any reference to your specific roof size, shape, or access, that is a warning sign. The right system depends on deck condition, whether there are any penetrations or rooflights, the size of the roof, and budget. Ask the contractor to explain why they are recommending what they are recommending.
The deck is the structural base the membrane sits on - usually timber boards or plywood on residential properties. A quote given without inspecting the deck is not a reliable quote. Rotted or wet boards need replacing before any membrane goes on. If a roofer quotes you from the ground or from a photo, ask how they plan to account for deck condition. A reputable contractor will inspect first and confirm the price once they know what they are dealing with.
The membrane itself rarely fails in the middle of a flat roof. Water gets in at the edges - where the membrane meets the fascia board, where it turns up against a wall, or where it wraps around a parapet. Ask the contractor specifically how they will detail these junctions. The answer should include aluminium trim or lead flashing at the perimeters, and the membrane should turn up at least 150mm against any adjoining wall.
Most flat roofs on single-storey extensions or garages can be reached with a ladder and crawl boards. If the roof is above a two-storey structure or is otherwise difficult to reach, scaffolding or a tower may be needed. Ask whether access equipment is included in the price, and clarify who is responsible for arranging it. Scaffolding adds cost - typically £400 to £900 for a straightforward domestic job - but cutting corners on access means unsafe working and poor-quality detailing at height.
Photographs of completed jobs are useful, but a portfolio of photos does not tell you how those roofs are performing two or three years later. Ask whether the contractor can point you to any recent customers who would be willing to speak to you, or whether they have any projects you could drive past. Local work you can actually look at is more useful than a gallery of images.
Get the quote in writing and read it carefully. A well-written quote will specify the system being used, the number of layers or the membrane thickness, what happens if deck boards need replacing, how the edges and flashings will be finished, and what the price does not include. If a quote is a single line and a number, ask for a breakdown. Gaps in a quote become disputes when the job is under way.
On a typical extension or garage flat roof in and around Little Shelford, the sequence runs like this. The old covering is stripped back to the deck. The deck is inspected - any soft, wet, or damaged boards are replaced at this stage. The fall is checked; if it needs correcting, firring pieces or a new tapered layer are added. An edge trim is fitted around the perimeter. The EPDM or felt is laid, bonded, and rolled out. Upstands are formed where the roof meets any wall, and lead or aluminium flashing is dressed over the top. The job is then walked and checked for any bubbles, gaps, or lifted edges before the site is cleared.
On a straightforward garage roof, this typically takes one to two days. A larger or more complex extension roof with rooflights or multiple changes of level may take three to four days. If the deck needs significant replacement, add time accordingly.
Replacing a flat roof on an existing structure is generally considered maintenance and does not require planning permission. If you are extending the structure at the same time, different rules apply. If your property is listed or in a conservation area, check with the relevant authority before any work starts. Always let your immediate neighbours know before scaffolding goes up - it is good practice and avoids unnecessary disputes.
If you have a flat roof on your home, extension, or garage in Little Shelford and you want an honest assessment of its condition, call Cambridge Roofers to arrange a roof survey. We will tell you what we find, what your options are, and what the work is likely to cost - before you commit to anything.
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Call any time. Calls are answered day and night and passed straight to our roofers.
