Flat roofs on rear extensions and garages in Southborough face a specific challenge — the elevated ridge position means wind uplift forces are higher than in sheltered valley locations. GRP and EPDM systems are our recommendation here: seamless, mechanically fixed, and unaffected by the wind loading that fails felt lap joints.
Post-war extensions throughout Southborough are generating consistent flat roof replacement demand as original felt systems reach end-of-life. We install GRP and EPDM as primary systems, with felt as a budget option where the application allows.
Our most-specified system in Southborough. Fully seamless — no joints or laps for wind to work under. The fibreglass laminate is rigid enough to resist the uplift forces on an exposed Southborough ridge property. 20–25 year system warranty.
Single-ply rubber for larger or more complex flat roof shapes. Superior flexibility accommodates thermal movement — important in Southborough where temperature differential between exposed and sheltered faces is significant. 20-year warranty.
Three-layer polyester-reinforced felt as a budget option for straightforward surfaces in sheltered positions. Not our first recommendation for fully exposed Southborough ridge properties but appropriate for protected rear extensions.
Wind-driven rain loads flat roofs hard on exposed Southborough properties. Correct drainage falls, properly sized outlets and drip edges are non-negotiable. We survey existing drainage on every flat roof installation and rectify poor falls before installing the membrane.
The majority of flat roof replacement calls we receive from Southborough are on post-war rear extensions — single-storey kitchen and utility extensions built between 1950 and 1985 with original three-layer felt that has either split at the laps or developed surface blistering. At elevation in Southborough, UV exposure is marginally higher than the valley floor, and wind uplift on exposed rear extensions accelerates lap failure in older felt systems. The correct replacement is a fully bonded GRP or mechanically fixed EPDM system — neither relies on lap adhesion that wind can work at.
Flat roof installations in Southborough also need to account for higher-than-average rainfall intensity compared to lower-lying Kent locations. The drainage specification for a Southborough flat roof should use larger outlet sizes than a standard Kent installation would require. We use a minimum 68mm diameter outlet on all Southborough flat roof installations and calculate falls to ensure no ponding occurs under any rainfall intensity.
Call 0173 224 1138 for a free, no-obligation survey and written quote. We cover Southborough and the surrounding area from our Tonbridge base.
Typical price ranges. All quotes are free, written and fixed-price. Call 0173 224 1138.
| Job Type | Typical Cost | Timescale |
|---|---|---|
| GRP fibreglass — small extension (up to 15m²) | £900–£1,800 | 2–3 days |
| GRP fibreglass — medium (15–30m²) | £1,800–£3,500 | 3–5 days |
| EPDM rubber — garage or large flat (30m²+) | £2,500–£5,000 | 4–6 days |
| Torch-on felt (3-layer, per 10m²) | £600–£1,200 | 1–2 days |
| Deck replacement (included with membrane) | Add £200–£600 | — |
"GRP on the rear extension after the old felt let go completely. Excellent workmanship — smooth finish, correct falls, all drainage outlets properly positioned. Came in on quote exactly."
"EPDM on a large L-shaped flat roof covering the kitchen and utility. Complex shape but installed without issue. No ponding after the first heavy rain — drainage was specified correctly."
"Old felt on the garage roof had been patched three times. Finally had it done properly with GRP. Should have done it years ago — no more annual patching."
GRP fibreglass is our recommendation for exposed positions — it's fully seamless and rigid, with no lap joints for wind to work under. EPDM is the alternative for larger or irregular shapes. Felt is not recommended for fully exposed Southborough ridge positions.
Small extension (up to 15m²): 2–3 days including preparation. Medium (15–30m²): 3–5 days. We don't rush GRP installations — curing time is critical to the 25-year warranty.
GRP on a small extension: £900–£1,800. Medium extension: £1,800–£3,500. EPDM on a large garage: £2,500–£5,000. Free survey and written fixed-price quote on 0173 224 1138.
Yes — 10-year workmanship guarantee in writing on all flat roof installations, plus the manufacturer's system warranty (20–25 years on GRP, 20 years on EPDM).
GRP fibreglass for most extensions up to ~40m². It's seamless and handles Kent conditions well. EPDM for larger or more complex shapes. We specify after a free survey.
Isolated splits, blisters or failed outlets can often be repaired. Once the deck has absorbed moisture, or membrane failure is widespread, replacement is better value. Free survey confirms which applies on your Southborough property.
Standard survey appointments are available within 2–3 working days in Southborough. Emergency same-day calls taken any time on 0173 224 1138. For planned work, 1–2 weeks lead time is typical during busy seasons.
No call-out fee. No obligation. We serve Southborough from our Tonbridge base.
0173 224 1138 ✉ Email Us