Understanding exactly what happens when a flat roof is replaced in Lakenheath helps you know what to expect, ask the right questions, and spot whether the job has been done properly.
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A flat roof replacement is not a job that should be quoted from the pavement or agreed over the phone without anyone getting eyes on the roof. The process, done properly, follows a clear sequence from the initial survey through to the final clean-up. Knowing each step gives you a basis for comparing roofers and understanding what you are paying for.
Thetford Roofers covers Lakenheath and the wider area from our base in Thetford. On this page we walk through the full process of a flat roof replacement - what happens at each stage, why it matters, and what you should expect to see happening on your property.
A proper survey means physically getting onto or as close as possible to the roof, not just looking from a ladder at the edge. The roofer should be checking the surface of the existing covering for splits, blistering, open laps and areas of standing water. They should also be checking the falls - the direction and degree of slope - and whether the outlets or drip edges are clear and functional.
At wall junctions - where the roof meets a brick or rendered wall - the flashing needs inspecting. Lead or aluminium flashing that has dropped away from its mortar joint, or which has split at a fold, is a common source of leaks that look like a membrane failure but are not.
The roofer should also press or walk the deck surface to feel for soft spots, which indicate rot in the boards or plywood beneath. A deck that feels spongy will need sections replacing, and this should be discussed at survey stage rather than presented as an extra cost once work has started. Ask directly: what do you expect to find when the old covering comes off?
On most replacement jobs the first task on site is stripping the existing felt or membrane down to the deck. This is important because overlaying a new system on top of a failed old one traps moisture in the deck and shortens the life of the new installation. Stripping also gives a clear view of the deck condition for the first time.
During stripping, watch for how the waste is handled. Old bitumen felt is heavy and awkward. A good crew will have a skip or bags on site and will not leave stripped material on your garden or driveway for days. The roof should not be left open overnight in unsettled weather - if a full strip and recover cannot be completed in the same day, the exposed deck should be temporarily covered at the end of each working day.
Once the old covering is off, the full condition of the deck is visible. Decks are most commonly 18mm or 22mm tongue-and-groove timber boarding, or structural plywood. Both can rot when water has been getting through over a period of months or years.
Rotted sections should be cut back to sound timber and replaced with new board of the same thickness. If only one or two boards have failed, the cost is modest. If a large area of the deck has softened, the cost of deck replacement can match or exceed the cost of the new covering, and you should be told this before the job is agreed rather than during it.
The deck also needs to be structurally fixed at this point - any boards that have lifted, any noisy fixings, any areas where the deck has deflected and created a low spot. Falls can sometimes be improved at this stage using tapered insulation boards, which are laid over the deck to create or correct the slope before the new membrane goes on. This is worth asking about if your roof has a history of ponding.
The method for laying the new covering depends on which system has been specified. For EPDM rubber - the most common system for residential flat roofs today - the process involves priming the deck, applying contact adhesive to both the deck and the underside of the membrane, then carefully rolling the sheet out and pressing it down to achieve a full bond. Joins, where they exist, use a specific lap tape and seam primer. The whole sheet needs to bond fully with no air pockets or creases, because either will cause the membrane to lift at the edges over time.
For torch-on felt, the installer uses a gas torch to heat the underside of the sheet as it is unrolled, bonding it directly to the layer below. Each lap - the overlap between sheets - needs thorough torching to create a watertight seal. The base layer is nailed or mechanically fixed to the deck, and the cap sheet is torched on top.
Regardless of system, the covering should extend to a clean edge or upstand all the way around the perimeter. A membrane that stops short of the edge, or that has been tucked under a trim but not properly bonded, will lift in wind or allow water to track underneath.
Edge finishing is where many flat roofing jobs fall short. A drip edge - typically an aluminium or galvanised trim fixed to the fascia or timber edge - should be in place before the membrane is laid, so the covering can be taken over it and down onto its face. This directs water cleanly into the gutter rather than allowing it to run back under the edge.
At wall junctions, the upstand - the section of membrane turned up against the wall - should be a minimum of 150mm high. Lead flashing is then dressed over the top of this upstand and into a raked mortar joint in the brickwork, sealed with appropriate pointing. On rendered walls, lead is cut into a chase rather than a mortar joint. Both should be sealed with a suitable mastic, not ordinary sand and cement, which cracks with movement.
Outlets should be cleaned out and checked during installation. Where an outlet collar is worn or the seal has degraded, it is far simpler to replace it during a full recover than to return to it later. A bonded outlet collar - sealed into the membrane rather than just sitting on top of it - is the correct detail.
Before leaving site, a roofer should walk the finished roof and check the whole surface, all edges, all flashings and all outlet details. Any area that sounds hollow when tapped - indicating the membrane has not fully bonded to the deck - needs pressing back down while the adhesive is still workable or re-primed and re-bonded.
Gutters should be cleared of any debris from the job. If any clips, fixings or trim were disturbed during edge work, they should be refitted. The surrounding area - garden, driveway, paths - should be checked for waste material and swept clear.
Ask to be shown the finished edges, flashings and any outlet details before the crew leaves. These are the points most likely to be the source of any future problem, and seeing them yourself while the roofer can explain what was done gives you a useful record of the installation.
A flat roof replacement in Lakenheath and the surrounding area typically costs between £70 and £120 per square metre for a complete installation, covering strip-off, deck repairs where needed, new membrane, edge trims and flashings. The system chosen - EPDM or torch-on felt - affects the price, as does the size of the roof and whether significant deck replacement is needed. Bay window roofs of under 10 square metres usually attract a minimum charge because the setup and access time are the same regardless of area.
Thetford Roofers works across Lakenheath and the surrounding area.
If your flat roof needs attention - whether that is a repair, a survey to assess its condition, or a full replacement - call Thetford Roofers. We will inspect the roof properly, talk you through what we find, and explain the work in plain terms before any commitment is made.
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Call any time. Calls are answered day and night and passed straight to our roofers.
