If you have never had a flat roof replaced or installed, knowing exactly what happens from the first visit to the final tidy-up helps you plan and know what to expect.
Call any time. Calls are answered day and night and passed straight to our roofers.
A flat roof replacement or new installation is not a complicated job in the right hands, but there are a number of distinct stages and each one matters. Skipping steps or rushing any part of the process is where problems come from later. This page walks through what a properly managed flat roofing job looks like, from the initial assessment right through to clearing up and leaving site.
We cover Sprowston and the wider area around Norwich, including Thorpe St Andrew, Thorpe, Hellesdon and Taverham. The process is the same wherever we work.
Before any price is agreed or work planned, the roof needs to be looked at properly. That means getting up on it, not just looking from the ground or from a ladder. A good assessment checks the condition of the existing membrane, the deck beneath it, the flashings and upstands, the drip edge and fascia, and the drainage outlets.
On a repair job, the assessment should identify whether the leak source is the membrane itself, a failed flashing, a blocked outlet, or a problem at a junction with a wall or skylight. These are different problems with different solutions, and misdiagnosing them leads to failed repairs.
For a full replacement, the assessment establishes whether the existing deck is sound enough to work off, or whether it needs to come out. It also confirms the roof area, the fall direction, the edge details needed, and any complications such as parapet walls, roof lights or drainage outlets that need working around.
Ask any roofer to explain what they found during the assessment and why they are recommending what they are. If they cannot do that clearly, that is a concern.
Once the assessment is complete, the specification for the job should be set out in writing. This should state clearly what material system is being used, how many layers, what the deck will be (if new boards are needed), how the edges will be finished, what flashings are included, and how drainage will be handled. A price that does not specify these things is hard to compare against other quotes and easy to dispute later.
For homeowners, a written job specification is the single most useful document you can have before work starts. It defines exactly what you are paying for.
On a replacement job, the existing roof membrane and any failed insulation boards come off first. On older roofs, this sometimes reveals more damage to the deck than was initially visible from above. Saturated or rotten deck boards must be cut out and replaced - bonding a new membrane over damaged timber is not a fix.
Stripping also gives the roofer a clear view of how the existing falls work and whether any corrections are needed. If the fall is insufficient, this is the point at which it can be addressed with tapered insulation before the new deck goes down.
Expect a skip or a large pile of debris on the day stripping takes place. The old felt and deck boards are heavy material. Good contractors will have arranged disposal in advance rather than leaving it for the customer to sort out, but it is worth confirming this before work begins.
If the existing deck is sound - typically 18mm marine-grade plywood - and the falls are correct, the deck is cleaned, swept and checked for any remaining soft spots or protruding fixings before the new membrane goes down. Loose boards are re-fixed. Any penetrations or pipe outlets are checked and prepared.
If new deck boards are needed, they are cut and fixed to the joists below. The fall should run consistently from the highest point to the outlet - usually a corner or an edge with a gutter. On a new installation, the joists are set to create the fall before the deck goes on at all.
Insulation boards, where specified, are laid on top of the deck before the membrane. Tapered insulation boards are cut to a wedge profile to create or improve the fall. Rigid insulation on a warm-roof configuration sits above the deck and below the membrane, keeping the roof structure warmer and reducing condensation risk inside the building.
The method at this stage depends on the system chosen.
For EPDM rubber roofing, the membrane is typically supplied in a single sheet cut to size before it goes up. The deck is coated with water-based bonding adhesive, the membrane is carefully positioned, and then rolled out into the adhesive from one end to avoid trapping air. Edges are folded up the upstands and trimmed. The perimeter is secured with aluminium or EPDM edge trim, bonded or mechanically fixed. Seams, where they exist, are made with special EPDM seam tape and primer, not standard adhesive.
For torch-on felt, each layer of polyester-reinforced bitumen membrane is heat-bonded to the surface below using a gas torch. The first layer bonds to the deck, subsequent layers bond to the layer below. The installer moves slowly and steadily, melting the underside of the membrane and pressing it down as they go. Edges and upstands are detailed with cut pieces, also torched in. A cap sheet with a mineral or slate-chip surface goes on last.
In both cases, the upstands at any wall junction must be dressed up at least 150mm above the finished roof surface - this is a standard requirement to prevent water backing up behind the membrane at the most vulnerable point.
Flashings at the wall junction and any penetrations are fitted after the membrane. On most domestic flat roofs, lead or code-matched aluminium flashing is used. The flashing is dressed down over the top of the membrane upstand and tucked into a mortar joint in the brickwork above, then pointed back in.
The drip edge at the bottom of the roof must direct water cleanly into the gutter. A properly fitted aluminium or lead drip edge is dressed over the fascia and the membrane is bonded or mechanically fixed tight against it. Where there is no fascia - such as on a parapet wall - a suitable coping or upstand detail is used instead.
Flashings are where flat roofs most often fail, so this stage deserves as much care as the membrane itself. On a new or replacement job, all flashings should be new - reusing old flashing over a new membrane is a false economy.
Once the membrane and flashings are complete, the drainage is checked. Outlets should be clear and positioned at the lowest point of the fall. Water should run freely from any point on the roof surface to the outlet or gutter. On EPDM roofs, an outlet collar bonded into the membrane is the proper detail - not just a hole cut through with a loose outlet sitting in it.
A final walk-over inspection checks for any lifted edges, unbonded seams, or flashing points that need extra attention. Good practice is to check the roof after the first significant rainfall to confirm the falls are working as intended.
All off-cuts, packaging, old felt and deck waste should leave site with the contractor. The gutters should be checked and cleared of debris from the job before the roofer leaves. Scaffolding or tower sections come down on completion.
Ask the contractor to walk you round the finished job and show you the drain outlets, any flashing points, and the edge details so you know where to look if you ever notice a problem later.
We work across Sprowston, nearby Thorpe St Andrew, Thorpe, Norwich and surrounding areas. If you need a flat roof replaced or repaired, call Poringland Roofers to arrange an assessment and a clear, itemised quote for the work.
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Call any time. Calls are answered day and night and passed straight to our roofers.
