Flat Roof Replacement Cost in South Yorkshire (2026)

Straight answer first: a full flat roof replacement in South Yorkshire typically costs £950 for a small porch roof, £1,800 for a single garage, and £5,400 for a rear extension done to warm-roof spec — stripped, rebuilt and guaranteed for 20 years.

This guide covers what a flat roof replacement actually includes, when you shouldn’t replace at all, how the three main materials compare on real lifetime cost, and how to spot a quote that’s cheap for the wrong reasons.

Flat roof replacement cost by roof type

Roof type	Typical size	Typical price
Bay window / porch	~6 m²	£950
Single garage	~15 m²	£1,800
Double garage	~25 m²	£2,650
Dormer / loft conversion	~20 m²	£3,400
Rear extension (warm roof spec)	~40 m²	£5,400
Small commercial unit	~120 m²	£14,500

Those are genuine ballparks from our most common jobs — the same figures behind our 60-second estimator. Every replacement includes the strip-out, deck checks, all flashings and trims, waste removal, and a 20-year manufacturer-backed warranty plus our own 20-year workmanship guarantee.

If you want the deeper per-square-metre breakdown, we’ve published a full single ply cost guide for South Yorkshire — this page is about the replacement job; that one is about the numbers behind it.

Replace or repair? Do this sum first

Replacement isn’t always the right call, and we’ll tell you when it isn’t. The honest rule of thumb:

• Repair if the roof is under ~15 years old, the leak is local (a split, a failed flashing, one bad seam), and the deck underneath is dry. Repairs run £250–£1,500.
• Replace if the covering is past 15 years, it’s leaked in more than one place, water is tracking under the covering, or you’re already patching it every winter. At that point every repair is money thrown at a roof that’s finished.

A useful test: if a proper repair quote comes to more than a third of replacement cost — or it’s the second repair in two years — replace. Here are the 7 warning signs your flat roof needs replacing if you’re on the fence, and our repair price guide if you’re not.

Felt vs GRP vs single ply: cost per roof, not per quote

System	Upfront cost	Realistic lifespan	Roofs you’ll buy in 40 years
Felt	£40–£60/m²	10–20 years	2–3
GRP fibreglass	£70–£90/m²	10–15 years in practice	2–3
Single ply	£70–£100/m² (ours from £90/m²)	40+ years	1

Felt is the cheapest quote you’ll get, and around Rotherham and Doncaster we strip out failed felt every week — here’s the full felt cost breakdown. GRP looks smart on day one but cracks at the joints as the building moves, which is why we don’t fit it at all.

Single ply costs more on the day you fit it and less every year after. One membrane, heat-welded seams, 20-year warranty, 40+ year design life. Fit it once and stop thinking about your roof.

What a proper replacement includes (and takes)

A typical domestic replacement runs 1–3 days:

1. Strip-out — old covering off, down to the deck. This is where surprises live: a soggy chipboard deck or rotten joists get flagged and priced before any new material goes down, never invoiced as a mystery extra.
2. Deck and build-up — new insulation if you’re going warm roof (+£40/m², and often the smart move under living space — it’s usually the trigger for building-regs insulation requirements too, which we handle).
3. Membrane and details — single ply fitted to the manufacturer’s spec: welded seams, proper upstands, trims, outlets and flashings. The details are where 20-year roofs are made — it’s what our SPRA award was for.
4. Waste away, warranty in writing — skip gone, paperwork in your hand.

Scaffolding, where a roof needs it, adds £1,000–£2,000 and is itemised on the quote up front.

How to compare replacement quotes without getting burned

Getting three quotes? Good. Compare them on these five lines, not just the bottom number:

• Is the spec written down? Membrane brand, insulation thickness, deck treatment. “New rubber roof — £X” is not a spec.
• Whose warranty is it? A manufacturer-backed warranty survives the installer; a verbal “guarantee” doesn’t. Ours are 20 years and transferable if you sell up.
• Is the strip-out included? Overlaying rotten felt is how £3,000 roofs fail in year two.
• Is waste removal included? Skips aren’t free; surprise invoices are worse.
• Can you see their work? We publish full case studies and every one of our Google reviews is real and checkable.

We’re happy to be quote number three — how we work is built for people comparing.

Flat roof replacement FAQs

How long does a flat roof replacement take? Most domestic roofs — garages, extensions, dormers — take 1 to 3 days including strip-out. Weather can stretch that; we don’t open up more roof than we can make watertight the same day.

Can I stay in the house during the work? Yes. It’s noisy overhead for a day or two, but there’s no need to move out — we keep access clear and the site tidy at the end of every day.

Will a new flat roof add value to my house? A documented, transferable 20-year warranty answers the exact question every buyer’s surveyor asks about a flat roof. It won’t add a bedroom’s worth of value, but it removes a common reason for price-chipping at sale.

Do you replace flat roofs everywhere in South Yorkshire? Yes — we’re based in Kilnhurst, so Rotherham, Doncaster, Barnsley and Sheffield are all local rates, local crew. There’s a town-level price example in our Mexborough replacement guide.

Is winter a bad time to replace a flat roof? Single ply is heat-welded, not glued or resin-cured, so it goes down properly in cold weather when felt torch-on jobs and GRP resins struggle. If your roof is failing in November, don’t nurse it until spring.

Get a replacement price for your roof

Two ways, both free, neither involves a salesman on your sofa:

• Price your roof in 60 seconds — instant range, no phone number needed to see it
• Or ring Chris on 07807 815181 — he surveys every job himself and will tell you straight if a £350 repair is the right answer instead

Prices correct as of July 2026. Guide figures come from our own recent South Yorkshire jobs.