Flat roofing in Luton

Can a leaking flat roof be patched?

Often, if the deck underneath is sound and the leak is in one place. A split in felt, a lifted seam on a rubber roof or a failed upstand where the roof meets a wall can each be repaired on its own. If the deck is soft underfoot, water ponds across large areas, or the covering is blistered and cracked all over, a patch will not last and renewing the covering is the better use of your money.

We check from above and, where we can, from inside the garage or extension, because ceiling stains and a sagging deck show how far water has spread. Then we tell you which route we would take and why.

EPDM, GRP or felt: which suits your roof?

Each has its place, and the drawing shows how they are built up.

• EPDM is a synthetic rubber sheet, laid in one piece on most small roofs, so there are few or no joints to fail.
• GRP is glass-fibre matting set in resin under a coloured topcoat. It sets hard, handles awkward shapes and edges well, and needs dry weather to lay.
• Built-up felt is two or three layers of reinforced bitumen membrane under a mineral-faced cap sheet, far tougher than the single layer of felt on many old garages.

We tell you which we would use on your roof and why. Our guide to EPDM, GRP or felt sets out the trade-offs.

How long does a new flat roof last?

The fairest answer is what each product's certificate states, and it varies by system. These are the makers' certified figures for their own products when installed as specified. They are not a promise from us.

System	Certificate	What it says
ClassicBond EPDM, non-reinforced	BBA 22/6065	"will have a service life of at least 35 years"
ClassicBond PRO EPDM, fleece reinforced	BBA 22/6065	"service life of at least 35 years"
Firestone RubberCover EPDM	BBA 89/2216	"a life of at least 30 years"
Topseal GRP	BBA 93/2932	"durability in excess of 15 years", adding that a well-formed laminate "can maintain its integrity for 30 years"
Cure It GRP kit	ETA 20/0908	working life "25 Years" (the LRWA adds that it "does not test products")
IKO Ultra Prevent bitumen membrane	NBS Source listing (BBA 91/2671)	"a life expectancy in excess of 25 years", from IKO's NBS Source listing rather than the certificate itself

Workmanship decides whether a roof gets near those figures. Laps, upstands, edge trims and outlets are where flat roofs give way, so those are the details we spend longest on.

What fall does a flat roof need?

Enough for water to run off rather than sit in puddles. BS 6229:2025, the code of practice for flat roofs, sets "a minimum 1:80 finished fall for general roof areas and internal gutters", and calls for a level survey and a documented handover. Because decks and joists are never perfectly true, the ClassicBond PRO certificate says to design for twice the minimum finished fall, which works out at 1:40 to achieve 1:80.

A roof laid nearly level will pond whatever it is covered with. When we renew one we check the fall with a level and, where it falls short, build it up with firrings or tapered insulation before the new covering goes down.

Does a replacement flat roof need insulating?

Often, yes. Approved Document L counts replacing the waterproof membrane on a flat roof as renovating a thermal element. If more than half of the roof's surface is renovated, the whole element should be upgraded, to a U-value of 0.16 W/m²K unless that would not pay back within 15 years, in which case the best level that does pay back applies. Planning Portal puts it simply: "you may be required to upgrade this 'thermal element'".

Insulation on top of the deck raises the roof, so we check upstands, door thresholds, windows and the wall flashing before we price. Replacing a roof covering is also work GOV.UK says you must tell a building control body about, unless the roofer is registered with a competent person scheme. Ask any roofer which route they will use, and make sure you get the certificate at the end. New regulations take effect on 24 March 2027 under building circular 01/2026, which does not say whether the figures for existing homes will change.

Does a flat roof near the boundary need a fire rating?

Yes, and it decides which systems can be used. Guidance from the LRWA, NFRC and SPRA (March 2024) says a flat roof system classed BROOF(t4) can be used without restriction on distance to the boundary, while a CROOF(t4) system needs to be at least 6m away. The rating applies to the system as installed. Rear extensions on terraced and semi-detached houses are often closer than 6m to the boundary, so a system with a BROOF(t4) rating is the safe choice there; ask any roofer for the fire certificate that covers the system as installed.

What should you check on an old garage roof first?

Whether it contains asbestos. Stevenage Borough Council lists garage and shed roofs among the places it turns up, and HSE's house diagram includes profiled asbestos cement sheeting and roofing felt. Asbestos "can be present today in any building built or refurbished before 2000", so on an older garage we do not cut, drill or break the roof until it has been tested. Stevenage's advice is to "please leave it alone; it is usually safe unless damaged or disturbed."

What does a new flat roof cost?

For a single garage, national guides put it in the low thousands. Which? (22 October 2026) gave £1,400 to £3,500 for felt on a 6m by 3m single garage and £1,950 to £4,000 for other materials, excluding VAT. Checkatrade, updated February 2026, gives £2,800 to £7,500 for a standard flat roof replacement. Those are not our prices: we measure your roof and give a written price for the system we recommend, the same as for any job from our team of Luton roofers. Our guide to roof repair costs covers smaller repairs.

Questions people ask us

How long does an EPDM roof last?

The BBA certificates give at least 30 years for Firestone RubberCover and at least 35 years for ClassicBond; how well the roof is laid decides whether it gets there.

Do I need building regulations approval to replace a flat roof?

GOV.UK lists replacing flat roof coverings as notifiable work unless the roofer is registered with a competent person scheme, so ask whoever you use how the work will be signed off.

What is the minimum fall for a flat roof?

BS 6229:2025 sets a minimum finished fall of 1:80, and roofs are designed steeper than that so the finished surface still reaches it.

Is GRP or EPDM better for a garage?

Both suit a garage. EPDM goes down in one sheet with few joints, while GRP copes well with awkward edges and details; we explain which fits your roof, and a roof inspection can check the deck first.

Sources and further reading

• ClassicBond Non-reinforced EPDM, BBA Certificate 22/6065, first issued 27 Oct 2022
• ClassicBond PRO Fleece Reinforced EPDM, BBA Certificate 22/6065, first issued 27 Oct 2022
• Firestone RubberCover EPDM System, BBA Certificate 89/2216, 2nd issue 27 Nov 2018
• Topseal Roof Waterproofing System (GRP), BBA Certificate 93/2932, first issued 24 Sep 2009
• Cure It Composites (product register entry; ETA 20/0908), LRWA
• IKO Ultra Prevent roofing systems, NBS Source (BBA 91/2671)
• BS 6229:2025 update: key points for members, NFRC, 18 Dec 2025
• Approved Document L Vol 1: Dwellings, 2021 edition incorporating 2023 amendments
• Building regulations: Re-roofing, Planning Portal, undated (© 2026)
• Building work, replacements and repairs to your home, GOV.UK (shows "Updated 3 November 2014"; metadata 2026)
• The Future Homes and Buildings Standards: building circular 01/2026 letter, 24 Mar 2026
• Changes in fire regulations for flat roofs (guidance V3), Mar 2024
• Asbestos, Stevenage BC, posted 16 Oct 2026
• Diagrams showing where asbestos can occur in buildings, HSE
• Asbestos: why and where, HSE, updated 1 Mar 2021
• How much do roof repairs cost?, Which? (N. Turner, V. Purcell), 22 Oct 2026
• Flat roof replacement costs in 2026, Checkatrade, updated 02/26