Flat Roofing
Flat Roofing Specialists
in Bishop's Stortford & Hertfordshire
EPDM rubber, GRP fibreglass and high-performance felt flat roofs installed properly the first time — built to last 25+ years on garages, dormers, single-storey extensions and outbuildings.
Overview
Modern Flat Roofs That Actually Last
A flat roof done properly is one of the most reliable, low-maintenance coverings you can put on a UK property. A flat roof done badly is the most common source of leaks we get called to fix. The difference comes down to three things: the right system specified for the job, the deck preparation underneath it, and the detail at the upstands and trims.
We install three flat roof systems regularly — EPDM rubber for most domestic projects, GRP fibreglass where rigidity and aesthetics matter, and modern torch-on felt where budget is the deciding factor. We'll specify what's right for your roof, not what makes us the easiest profit.
Why It Matters
What Happens When a Flat Roof Goes Wrong
An ageing or badly installed flat roof rarely fails at the surface — it fails at the joints, the upstands and the trims. Once water tracks underneath the membrane, it spreads sideways across the deck and emerges metres from the actual entry point, making diagnosis difficult and damage extensive.
Common shortcuts we see: timber decks not properly fixed before the membrane goes down, drip edges omitted, upstands too low against adjoining brickwork, and felt overlaid on existing failed felt rather than fully stripped. Each of these turns a 25-year roof into a 5-year problem. Our roof repair team sees the consequences every winter.
Our Process
How We Deliver Flat Roofing
Survey & Spec
We inspect the existing roof and deck, identify any timber repairs needed, and recommend the right system for the application.
Strip & Prep
Old covering fully stripped, deck inspected and replaced where needed, falls corrected, all fixings checked and tightened.
Membrane Install
EPDM, GRP or felt installed to manufacturer specification with proper bonding, seam detail and drip edges.
Upstands & Trims
Lead or proprietary trims dressed in, upstands sealed against adjoining walls, downpipe outlets fitted.
Sign-off & Guarantee
Water test, final inspection, written workmanship guarantee plus manufacturer-backed system guarantee.
Benefits
What You Get with J&Co
25+ Year Lifespan
When properly specified and installed, EPDM and GRP systems routinely outlast their stated guarantees.
Manufacturer Guarantee
Approved installer guarantees passed directly to you on every system roof.
Single-Piece Membrane
Most domestic EPDM roofs installed as one continuous piece — no seams to fail.
Proper Deck Prep
Deck inspected, strengthened and corrected for fall before any membrane goes down.
Technical Detail
EPDM vs GRP vs Felt — Which Flat Roof System is Right?
EPDM rubber is our most-specified domestic system. Single-piece membrane on most garage and extension roofs, no joints to leak, 25+ year manufacturer-backed lifespans, and reasonably forgiving on small movement in the deck. Cost-effective, fast to install, and the right answer for most flat roofs we quote.
GRP fibreglass is rigid, seamless across the full roof, and arguably the best-looking option when the roof is visible from above. Slightly more expensive than EPDM, requires good weather conditions to install properly, but extremely durable and walkable. Often the right choice for balconies, dormers and high-spec extensions.
Modern torch-on felt is the budget option. Three-layer high-performance felt systems still give 15–20 years when laid properly. We install it where budget is the deciding factor, but we'll always be straight about the trade-off in lifespan compared with EPDM.
Whatever the system, the thing that decides whether a flat roof actually lasts is the prep underneath. We don't compromise on that. See also our roof repair service for any existing flat roof issues.
Honest Pricing
How Much Does a Flat Roof Cost in Hertfordshire?
Honest guide ranges below — every roof is quoted individually after a free site survey. We don't do day rates and we don't do open-ended pricing.
Garage flat roof (EPDM)
£1,800–£3,200
Strip and re-cover of a typical single garage including new trims and outlet.
Single-storey extension
£2,500–£4,500
EPDM or GRP on a typical 4m × 5m extension including any deck repairs.
Larger flat roof (>40m²)
From £4,500
Full system roof including upstand detail, drip trims and downpipe outlets.
What affects the price
- Roof size and shape
- System chosen (EPDM / GRP / felt)
- Existing deck condition
- Access and scaffold requirements
- Number of upstands and penetrations
- Insulation upgrades (if required)
Service Area
Areas We Cover for Flat Roofing
We deliver this service across our full Hertfordshire and Essex catchment. Regular projects in Bishop's Stortford, Sawbridgeworth, Harlow, Saffron Walden, Stansted Mountfitchet, Great Dunmow, Epping, Ware, Hoddesdon, Broxbourne, Cheshunt, Welwyn Garden City and Stevenage.
Outside this list? Call us with your postcode — we frequently work the wider London fringe and across the rest of Hertfordshire.
FAQs
Flat Roofing — Frequently Asked Questions
Get a Free Flat Roofing Quote
Owner-led survey, written itemised quote, manufacturer-backed system guarantee. Across Hertfordshire and Essex, seven days a week.
Page last updated: May 2026 · J&Co Builders Ltd · 1 Ugley Hall Cottages, Bishop's Stortford CM22 6JB