Fakenham Roofers handles flat roof installations and repairs in Holt, and this page walks you through exactly what a professional flat roofing job involves from start to finish.
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A flat roof job done properly looks straightforward from the outside. A roofer arrives, old material comes off, new material goes on, everyone goes home. But the steps in between - and the decisions made at each one - are what determine whether the roof lasts 5 years or 25. Understanding the process means you know what to expect, what questions to ask, and how to tell whether a job has been done properly.
What follows is a realistic account of how a flat roof replacement is carried out. Repair jobs follow a shorter version of the same sequence. We work across Holt and the surrounding area, and this is how a proper job runs.
Before a price can be given, someone needs to get up on the roof and look at it properly. A survey from ground level or from a bedroom window is not a survey - it is a guess. A roofer should access the roof surface, check the membrane condition across the whole area, look at every upstand and edge detail, press around any areas that look soft or discoloured, and check that the outlets and drainage are clear and correctly sized.
On the inside, the ceiling below the flat roof section should be checked for staining, damp patches or any sign of water tracking. Sometimes a leak enters at one point and travels along a joist before appearing at the ceiling some distance away, which can make the source difficult to identify without a proper inspection.
The fall of the roof also needs to be assessed. A correctly laid flat roof should have a minimum fall of 1:80, and ideally 1:40 or better. If there is no measurable fall, any new membrane will be laid onto a roof that still ponds water, which shortens its life. If the fall is wrong, this needs to be built up as part of the job.
Once the survey is done, the roofer should be able to confirm the exact scope of work. This includes the area of membrane to be replaced, how much decking needs to come up and be checked or replaced, what system is being installed, and how edge details and upstands will be finished.
If the old membrane has to come off before the deck condition is fully known, a responsible quote will set out a day-rate or a per-sheet rate for additional decking replacement if it is needed. That way there are no surprises when the old material comes off and the deck underneath is wetter than expected. Ask for this to be stated in any written quote you receive.
On most replacement jobs, the old membrane comes off first. Old felt roofs are stripped back to the deck, and the felt, insulation and any damaged board are removed and taken away as waste. This is the stage that sometimes throws up unexpected findings.
A common problem is discovering that a previous repair has been laid on top of an even older repair - layers of felt, bitumen paint and sand, all sitting on top of a deck that was never properly dried out after a previous leak. Getting all of this off and down to a clean, sound deck is essential groundwork. It is also the stage at which the true condition of the decking becomes clear.
Plywood and OSB decking that has been wet for some time may look acceptable until you press it. Soft or spongy boards need to come out. Leaving wet or rotten boarding under a new membrane will cause the membrane to move and debond, and will create ongoing damp in the roof space.
Once the old material is stripped, any damaged or rotten decking boards are replaced with new exterior-grade plywood - typically 18mm or as specified for the span. All new and retained boards should be checked for level, and any low spots or high spots in the deck should be addressed before any new material goes down.
On a timber joist flat roof, this is also the point at which tapered insulation can be laid to improve the fall if it is insufficient. Tapered insulation boards are cut to create a consistent slope across the deck. This is a more involved and more expensive option than a simple re-cover, but it is the correct solution where ponding water has been a persistent problem.
The deck surface should be clean, dry, and free of protruding fixings before the new membrane is laid. Any screws or nails that have worked loose need to be punched back down or replaced, as a high fixing under a membrane will cause a stress point and eventually a hole.
For EPDM rubber membrane, the installation process starts with laying out the membrane across the whole roof area before bonding begins. The sheet is sized so that it overhangs the edges and upstands, giving enough material to dress up the walls and over the fascia trim. Any joins in the membrane - necessary on larger roofs - are bonded with EPDM seam tape and roller-pressed to ensure full adhesion.
Bonding adhesive is applied to both the deck and the underside of the membrane in sections. The membrane is then folded back into the adhesive and pressed firmly across the whole area. This must be done on a dry day and in adequate temperatures - EPDM bonding adhesive does not cure correctly below around 5 degrees Celsius, so cold-weather installations require either heated working conditions or the job should not start. A roofer who bonds EPDM in freezing conditions is cutting corners that will show up later.
Once the field is bonded, the edges are dressed over the fascia trim or turned up the upstand and fixed with termination bar - an aluminium trim that holds the membrane edge flat against the wall and is sealed with compatible sealant. This edge detail is where the vast majority of flat roof failures occur, so it needs to be done carefully and checked before the roofer leaves site.
The edge of the roof needs a drip trim that carries water away from the fascia board and into the gutter. Without a properly fitted drip edge, water runs down the back of the fascia and rots it from behind. This is a detail that is easy to get wrong and causes significant damage over time.
Outlets and any roof drainage pipework should be checked and, if necessary, cleaned or replaced at this stage. A new membrane with a blocked outlet is a problem waiting to happen. The outlet collar needs to be bonded into the EPDM membrane with a specialist outlet insert and adhesive, not just pushed through a hole in the membrane and sealed with mastic.
Where the roof meets a wall - on a lean-to, a rear extension, or any parapet detail - the membrane must be taken up the wall to a minimum height of 150mm, and ideally higher. This upstand is secured with termination bar and the top edge is sealed. On a masonry wall, the sealant is normally applied into a chased groove or under the edge of a brick course.
Lead or aluminium flashings may be used in addition to the membrane upstand where the junction between roof and wall is more complex, for example around a chimney that rises through a flat roof. A thorough flashing detail at every wall junction is non-negotiable - this is where most water entry occurs on flat roofs that look otherwise sound.
A conscientious roofer will walk the whole roof surface after completion, checking that the membrane is fully bonded with no lifting edges, that every upstand termination is secure, that all outlets are clear, and that the edge trim is correctly seated. Any off-cuts, old material, and packaging should be removed from site on the day.
After the work is complete, a brief walk-round with the homeowner to show what has been done - and to point out any drainage or maintenance points worth knowing - is a reasonable expectation.
Flat roofing work can be carried out in most seasons, but very cold weather (below 5 degrees Celsius) affects EPDM adhesive curing and should be avoided. Autumn and spring tend to be the busiest periods as homeowners deal with problems found over summer or discovered once the rain returns. If you have a flat roof in Holt that needs attention, call us to arrange a survey and we can tell you what the job involves before any decisions are made.
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