If your flat roof in Long Stratton is showing signs of trouble, getting a straight assessment early saves you from a far costlier repair further down the line.
A flat roof is not truly flat. It sits at a shallow pitch - usually between one and five degrees - so that rainwater drains towards outlets rather than pooling in the middle. When that drainage is compromised, or when the waterproofing membrane breaks down, water finds a way in. Understanding the causes makes it much easier to spot problems before they become serious.
We work with two main systems on residential and commercial properties: traditional built-up felt and EPDM rubber. Both can give many years of reliable service when installed correctly and maintained sensibly. Both fail in recognisable ways when they are not.
The most obvious sign is a water stain on your ceiling directly below the flat roof area. It may appear after heavy rain or show up gradually as a slow tide mark. Either way, water has breached the membrane and is tracking through the roof structure. The longer it sits there, the more the timber deck beneath deteriorates.
Blistering on the surface of a felt roof is another clear indicator. Blisters form when moisture trapped beneath the felt layers expands in warm weather, pushing the surface up into bubbles. Once a blister splits - which happens as it flexes through seasonal temperature changes - the membrane is open to water ingress at that point.
Cracking or crazing across the felt surface, particularly at seams and around upstands, is a sign that the material has aged past its useful life. Felt becomes brittle over time as the bitumen oxidises. Fine hairline cracks may look superficial but they allow water to wick in during sustained rain.
Ponding water is a warning sign that is easy to dismiss. A small puddle that sits for more than 48 hours after rain means the fall of the roof is inadequate, the outlets are blocked, or both. Standing water accelerates the breakdown of any membrane system and adds weight load that the structure is not designed to carry continuously.
Lifted or separated flashings at the point where the roof meets a wall or parapet are a common entry point for water. Flashings are usually lead on better-quality installations. Where mortar has been used instead, it shrinks and cracks over time, opening a gap behind the flashing that channels water straight down the wall face.
Inside the property, look for damp patches on the wall just below the roof line, not just on the ceiling. Water entering through a parapet or flashing failure tends to run down the inner face of the wall before it shows on a ceiling, which can make the source hard to trace without a proper inspection.
Age is the most straightforward cause. A standard three-layer felt roof has a typical lifespan of around 15 to 20 years, though this varies considerably depending on installation quality and how much foot traffic it receives. EPDM rubber membranes tend to last longer - manufacturers commonly quote 25 to 50 years for the material itself, though the actual performance depends on how the system is detailed and fitted at edges and penetrations.
Poor original installation is a significant factor in early failure. Felt that is not properly bonded at laps and upstands, or that is laid over damp timber, will fail well before its time. A new flat roof laid directly over an existing failed one - without stripping back to check the deck - often traps moisture in the structure from day one.
Blocked outlets cause more damage than most homeowners expect. A single blocked drain can turn a flat roof into a shallow pond within an hour of heavy rainfall. Debris from nearby trees is the most common culprit. Clearing outlets twice a year, in autumn and spring, is a straightforward way to extend the life of any flat roof considerably.
Thermal movement is a factor that is easy to overlook. Roofing materials expand and contract with temperature. A flat roof in an exposed position can see surface temperatures swing from below freezing in winter to over 70 degrees Celsius in direct summer sun. Materials that are not properly accommodated for this movement - particularly at joints, upstands and where the roof meets other elements - will develop stress cracks and separations over time.
Physical damage from foot traffic is more common on roofs above extensions and outbuildings where people occasionally stand to clear gutters or access upper windows. Felt in particular is vulnerable to puncture and scuffing. EPDM is more resistant but still not designed for regular walking without protective walkway pads.
Torch-on felt (sometimes called modified bitumen felt) is a proven system that has been used on UK homes for decades. It is laid in multiple layers bonded with heat, giving a robust waterproof barrier. It suits most standard extension and outbuilding roofs and is generally the more economical option at the outset.
EPDM rubber is a single-ply membrane that is bonded or mechanically fixed to the deck. It handles thermal movement well, is highly resistant to UV degradation, and - because it comes in very large sheets - has far fewer seams than a felt system. Fewer seams means fewer potential failure points. For roofs with complex shapes or lots of penetrations, EPDM is often the stronger long-term choice.
Flat roofing costs depend on the system chosen, the condition of the existing deck, and the complexity of the detailing. A straightforward replacement on a single-storey extension will generally cost less than a roof with several outlets, upstands and lead flashings.
A thorough job starts with stripping the existing covering back to the deck so the timber can be inspected properly. Any soft, wet or delaminated boards must be replaced before the new membrane goes down - covering over a compromised deck just moves the problem forward. The deck surface needs to be clean, dry and firmly fixed before any new material is applied.
Drainage falls should be checked at this stage. If the existing falls are inadequate, tapered insulation can be added to correct the slope without altering the roof structure. This is also the point at which insulation can be upgraded to improve energy performance, since a stripped roof offers straightforward access.
All flashings, outlets and upstands should be detailed properly in the chosen system. On an EPDM installation this means bonded rubber at all upstands and purpose-made trim at edges. On a felt system it means full overlap at laps and proper sealing at all penetrations. Lead flashings should be correctly dressed into the wall and pointed with appropriate mortar or sealed with a compatible sealant.
When asking a roofer to quote, it is worth asking specifically whether the price includes stripping the existing covering, inspecting and replacing deck boards where needed, and detailing all flashings and outlets. A quote that does not cover those items will almost always cost more before the job is finished.
If you have spotted any of the warning signs above, or if your flat roof is more than 15 years old and has not been assessed recently, it is worth arranging a professional assessment. We will tell you honestly whether a repair will hold or whether a full replacement is the better use of your money.
No obligation · We usually respond within 2 hours
Storm damage, active leak, damaged ridge - we aim to be on-site within 24 hours.
