If you want to know exactly what a flat roofing job involves in Girton, from the initial look at your roof through to clearing up and leaving site, this page walks through the whole process.
No honest flat roofing quote should come from the ground. Before any price or recommendation is given, the roofer needs to get onto the roof and look at it properly. A visual check from the garden will not tell you whether the deck is wet, whether the fall is adequate, or what is happening at the flashings.
During the inspection, the roofer should walk the surface carefully, probing with a knife or bradawl at any suspect areas to check for softness in the deck beneath. Soft spots mean the plywood or chipboard decking has taken on moisture and begun to break down. The inspection should also cover every upstand, the condition of all flashings, the drainage outlet or outlets, and the edge trim or drip detail. This takes 20 to 30 minutes on a typical garage or extension roof and is the information that drives every decision that follows.
At this stage, the roofer should be able to tell you whether a repair is viable, whether an overlay is possible, or whether a full strip back to the structure is needed. Be cautious of any quote given before this inspection has taken place.
Once the inspection is complete, the scope of work needs to be clear before anything is ordered or booked. For a full flat roof replacement, the scope typically covers:
If insulation is being added or upgraded, that should be specified too, along with any work to fascias, soffits or guttering that the job requires. Having a clear written scope means there are no surprises when the job is priced up or when the work starts.
On a replacement job, the first physical task is stripping back the existing covering. On older felt roofs this means peeling back the layers of felt, often with a scraper and shovel. On a multi-layer roof this can take most of a morning on a single garage.
Once the felt is off, the deck is inspected again in detail. Problems that were not obvious under the old covering now show up clearly - rot in the corners, a low spot where water has been sitting, a section of decking that was patched in a previous repair and has since deteriorated. Any damaged boards are cut out and replaced with new plywood of the correct thickness, typically 18mm for a standard domestic flat roof. This is not optional: laying a new membrane over a soft or wet deck is the single most common reason a flat roof fails early.
All stripped material is loaded out and disposed of properly. This produces a significant volume of waste, and it is worth asking how the roofer plans to remove it from site before work starts.
A flat roof is not actually flat. It should have a fall of at least 1:40 (roughly 25mm per metre) to direct rainwater towards the outlet or edge. Many older roofs were either built without adequate fall or have sagged over time so that water now ponds in the middle or at the low corners.
Correcting the fall is done by tapering the insulation boards or by fitting tapered firring pieces (wedge-shaped timber strips) on top of the existing joists before the new deck goes down. This adds to the cost but is essential if the fall is inadequate. A new membrane laid over a ponding area will fail at the same rate as the old one, regardless of what material is used.
With the deck clean, dry and correctly prepared, the new covering goes down. For an EPDM system, the sheet is cut to size, laid out across the deck, and bonded down with contact adhesive. The adhesive is applied to both the underside of the membrane and the deck, allowed to tack off briefly, then the sheet is rolled into position. Edges are trimmed and turned up at any upstands, and the termination is secured with purpose-made aluminium trim and sealed with EPDM lap sealant.
For a torch-on felt system, the base layer goes down first, bonded with the torch, followed by the cap sheet. Each seam is fully welded, not just overlapped. A competent roofer will lift each seam briefly as they work to check the weld is complete. Partial seams are the single most common cause of torch-on felt failure.
Any penetrations through the roof - soil pipes, cables, rooflights - are sealed with purpose-made collars or hand-cut flashing patches. These details take longer than the main field of the roof but are the areas most likely to leak if they are not done carefully.
Flashings seal the junction between the roof covering and any adjacent vertical surface - the house wall, a parapet, a dormer cheek. On a typical extension roof, there is at least one abutment flashing where the flat roof meets the house wall. This is usually lead or aluminium, dressed into a mortar joint or fixed with clips and sealed.
Old flashings should be inspected at this stage and replaced if they are cracked, corroded or have pulled free from the wall. A new membrane with a failed flashing will still leak. Pointing up the mortar joint above the flashing is also good practice, as this is a common entry point for water that then tracks behind the lead.
At the opposite edge, the roof needs a drip edge or edge trim that directs water away from the fascia board and into the gutter below. On many older roofs this detail was skimped, leading to water running down the fascia and rotting the timber.
Before leaving site, the completed roof should be checked systematically. Every seam, every edge termination, every flashing joint and every outlet should be looked at. The outlet should run freely. Any sealant that has squeezed out onto adjacent brickwork should be cleaned off before it cures.
All waste from the job - stripped felt, offcuts, packaging - should leave with the roofer. Flat roofing waste includes bituminous material that cannot go in a standard skip without the right paperwork, and a professional roofer will deal with this as a matter of course.
The gutters adjacent to the roof should also be checked and cleared if leaves or debris have collected during the work. This takes ten minutes but prevents the first heavy rain from backing up against the new roof edge.
Newmarket Roofers carries out flat roof installations and repairs in Girton and across the wider area, including Newmarket, Cambridge, Histon and neighbouring villages. If you want a straightforward, no-pressure assessment of your flat roof, call us to book a proper roof-level survey.
No obligation · We usually respond within 2 hours
Storm damage, active leak, damaged ridge - we aim to be on-site within 24 hours.
