Ely Roofers carries out flat roofing installations and repairs for homeowners in Chatteris, and this page walks you through exactly what to expect at every stage of the job.
A flat roofing job is not complicated to understand, but it has distinct stages and each one affects the quality of the finished result. Knowing what a proper job looks like means you can ask the right questions before work starts, understand what is happening while it is underway, and check that it has been done correctly when it finishes.
What follows is an honest account of how a flat roofing job on a domestic extension, garage or outbuilding should be carried out from start to finish.
Before any price is given or any work is planned, the roof needs to be looked at properly. A visual assessment from the ground or a ladder can identify obvious problems - lifted flashing, surface cracking, blocked outlets, visible ponding marks - but it does not tell the full story.
A thorough flat roof inspection involves getting onto the roof surface and checking it methodically. We look at the membrane or felt condition across the full area, not just where a leak has been reported. We probe around upstands, outlets, and any pipe or vent penetrations, as these are the places failures most commonly begin. We check for soft spots by applying pressure across the deck - a spongy or deflecting section tells you there is moisture in the boards beneath. We also look at the drainage outlet and the condition of the surrounding gutter run.
Inside the property, we want to know where any damp has appeared, how long it has been there, and whether it varies with rainfall or temperature. This helps locate the entry point, which is often some distance from where the water shows up inside.
Once the inspection is done, the scope of work should be clear. There are broadly two outcomes: a repair where the existing deck is sound and the failure is localised, or a full re-cover where the membrane or felt has reached the end of its life or the deck has deteriorated across a wider area.
If it is a re-cover, the material choice is agreed at this stage - EPDM rubber or felt, and whether insulation is being upgraded at the same time. If any deck replacement is likely, this should be flagged before work starts, with an agreed rate for additional boarding, so there are no surprises when the old covering comes off.
A clear, written breakdown of what is included is important. Ask specifically: what happens if the deck is worse than expected? Is debris removal included? What drainage improvements, if any, are being made?
On a re-cover job, the old felt or membrane is stripped back to the deck. This is not optional or a preference - laying new material over old is poor practice. Trapped moisture between layers prevents proper bonding, causes blistering, and masks ongoing deck damage.
Stripping is physically demanding work and produces a significant volume of waste. Skips or large bags are standard for disposing of the old material and any rotten decking. If you have a driveway or path beneath the roof, protecting it during strip-out is worth discussing beforehand.
With the old covering removed, the deck boards are inspected in detail. Plywood and OSB (the most common deck materials on extensions and garages) will often show moisture damage in localised areas even when the roof has appeared sound from above. Soft, discoloured, or delaminating boards must be replaced - the new membrane is only as good as what it sits on.
Replacement boards should be screwed, not nailed, and any gaps between sheets filled or taped to give a smooth, continuous surface. If the falls (the slope of the deck towards the drain) are inadequate, tapered insulation boards can be fitted at this stage to restore or improve the drainage gradient. Checking that falls are still correct is a worthwhile step.
For an EPDM rubber roof, the membrane is cut to size and rolled out across the prepared deck. It is bonded to the deck using a contact adhesive applied to both the underside of the membrane and the deck surface, then pressed down and rolled out to remove any air. The membrane is taken up all upstands by at least 150mm and secured with a termination bar and sealant, or dressed into a raked-out mortar joint where it meets brickwork.
Outlets and pipe penetrations get purpose-made EPDM collars bonded in. These details are critical - a loose collar around a waste pipe or a poorly dressed upstand is where the next leak will start. Corners are formed with pre-moulded EPDM pieces rather than cut and folded, which gives a more reliable seal.
For a torch-on felt re-cover, the process differs. A base layer is mechanically fixed to the deck, then subsequent layers are torched down in overlapping runs. The top layer is a heavy cap sheet with a mineral or slate-chip surface. Each lap must be fully bonded with no bridging or short joints.
Lead flashings where the roof meets a wall are cut and dressed into the brickwork in sections no longer than 1.5 metres to allow for thermal movement. The chase in the mortar joint is raked out, the lead is tucked in and wedged, then pointed with appropriate mortar or sealant. Proprietary flashing systems (lead-free alternatives) are also available, though lead remains the traditional and long-lasting choice for most domestic applications.
Gutters and outlets are checked and cleared. If an outlet is positioned at a high point of the finished deck, the drainage needs to be re-thought - either the deck is adjusted or an additional outlet is added. Leaving a known drainage problem in place while fitting a new membrane simply moves the failure point into the future.
Once the membrane is down and flashings are complete, the roof surface is walked and checked methodically - every upstand, every lap, every penetration collar. Any adhesive smears are cleaned from brickwork and fascias. Waste from the job - old felt, rotten timber, packaging - is removed from site.
Before leaving, we talk the homeowner through what has been done, where the outlets are, and how to keep the roof clear of debris in future. A blocked outlet on a well-installed roof will cause problems; keeping it clear is straightforward maintenance that extends the life of any flat roof system.
A straightforward re-cover of a garage or single extension in Chatteris typically takes one to two days for a competent team. Larger roofs, extensive deck replacement, or complex detailing around multiple upstands and penetrations can extend this. Weather plays a part - EPDM can be installed in cooler conditions than torch-on felt, but rain during the installation of either system is a problem and any reputable roofer will work around it rather than through it.
A full EPDM re-cover on a typical garage or small extension (15-25 square metres) in the Chatteris area runs roughly £1,400 to £2,500 installed, depending on deck condition and drainage work required. Felt re-covers on the same area typically cost £900 to £1,800. Localised repairs - resealing an upstand, patching a small split - start from around £150 to £350. Deck replacement is charged additionally, usually per square metre of affected boarding.
Call us to discuss your flat roof and to arrange a survey.
No obligation · We usually respond within 2 hours
Storm damage, active leak, damaged ridge - we aim to be on-site within 24 hours.
