Immediate Steps
- Protect the interior — move valuables, place containers to collect drips
- Photograph everything — interior staining and any exterior damage visible from the ground, before touching anything
- Do not go on the roof — wet flat roofs are slippery and structural integrity may be compromised
- Call us — 0140 358 1272 — we attend Horsham flat roof emergencies and carry materials for same-visit make-safe
Finding the Fault
Flat roof leaks are deceptive. Water enters at one point and can travel along the deck or joists before dripping through internally. The stain is rarely directly below the entry point. The most common entry points on Horsham flat roofs are:
Outlet and Drainage Points
The area around the rainwater outlet is the highest-stress point on any flat roof. Water concentrates here, debris accumulates, and the transition between membrane and metal outlet is a common failure point. If the outlet is blocked and water has been ponding, the outlet perimeter is the most likely entry point.
Perimeter Flashings
Where the flat roof meets a wall or parapet, a flashing seals the junction. Lead or zinc flashing failure at this point allows water to run down behind the covering and through the deck. This is typically a repair rather than a full replacement.
Seams and Laps on Felt
Traditional felt laps are the Achilles heel of non-seamless systems. Once lap adhesive degrades or felt becomes brittle, water infiltrates the lap and tracks under the covering. On Horsham's aging felt stock — most now 20–40 years old — lap failure is the most common failure mode we find.
The Hidden Cost of Delay
A small flat roof leak left for three months becomes a deck replacement rather than a membrane repair. Water entering through a failed perimeter flashing or cracked outlet in September saturates the insulation and wicks along the deck boards through autumn and winter. By January, boards that were structurally sound in September are now soft and rotten across a much larger area than the original entry point. The repair cost in January is typically three to five times the cost of the repair in September. We see this pattern repeatedly — homeowners who noticed a small stain on the ceiling in summer and waited to see if it got worse, and then contacted us in winter when the ceiling was sagging.
GRP vs Emergency Felt Patch — Why We Recommend GRP
Emergency felt patches — bitumen mastic, torch-on patches, self-adhesive strips — are a temporary measure only. They extend a failing system's life by months, not years. If your flat roof is at or past end of life (over 20 years for felt, over 25 for EPDM), an emergency patch is a holding measure while you plan the replacement. It is not a repair. We will tell you this honestly during the emergency visit — if the system needs replacing, we say so and provide a replacement quote alongside the immediate make-safe. We do not charge for temporary repairs and then present a replacement quote two months later when the temporary fix has failed again.
Temporary Roofing Covers — When They Are Appropriate
Tarpaulin or temporary roofing membrane is appropriate as an emergency measure when the roof cannot be permanently repaired on the same day — for example, where materials need to be sourced, scaffold erected, or weather conditions prevent safe installation. We use purpose-made temporary roofing systems rather than domestic tarpaulins where a roof needs to remain covered for more than 24 hours. Temporary covers secured only at the edges can become sail-like in wind and cause additional damage. Our temporary covers are fixed at roof level to resist the wind speeds typical of West Sussex autumn storms.
Getting the Work Done in Horsham
All surveys in Horsham are free with no call-out fee. We attend within 3–5 working days for planned surveys and aim to reach emergency call-outs within 2–4 hours. Every job receives a written, itemised, fixed-price quote before any work starts — no verbal estimates and no bills that exceed the accepted written quote.
We are NFRC registered and carry £5 million public liability insurance. All work carries a written 10-year workmanship guarantee backed by a named, verifiable local contractor. Guarantee and insurance documentation is provided on request before any survey visit.
We cover Horsham and the surrounding West Sussex area including Roffey, Broadbridge Heath, Southwater, Billingshurst, Pulborough, Storrington, Henfield, Crawley, Burgess Hill, Haywards Heath, East Grinstead and Worthing. Call 0140 358 1272 to arrange a free survey.
Last reviewed: July 2026 by Horsham Roofing Experts.