Thetford Roofers replaces and repairs flat roofs on extensions, garages and bay windows for homeowners in Elmswell, with straightforward pricing advice before any work begins.
Flat roof pricing varies considerably, and vague answers frustrate homeowners trying to plan. The honest position is that costs depend on several specific factors, and understanding those factors lets you sense-check any quote you receive. Flat roof replacement in the UK typically costs somewhere between £70 and £120 per square metre for felt systems, and between £90 and £150 per square metre for EPDM rubber, but the final figure for your job could sit anywhere in those ranges depending on the variables below.
These are installed prices covering labour, materials and disposal of the old covering. They are not supply-only figures.
Roof area is the starting point for any flat roofing price. A small bay window roof might be five to eight square metres, a single garage is typically around fifteen to twenty square metres, and a rear kitchen extension can be anywhere from ten to thirty square metres depending on the house. Measuring accurately matters: a roofer who quotes without measuring on site may adjust the price once they see the actual area.
There is a cost efficiency that comes with larger roofs. Mobilisation, setup and travel are largely fixed regardless of the job size, so the per-square-metre rate on a twenty-five square metre extension tends to be lower than on a seven square metre bay window. If you have two small flat roofs to deal with, having both done at the same time is usually cheaper per square metre than doing them separately.
The timber decking beneath the existing covering is the single biggest cost uncertainty on any flat roof job. If the boards are in good condition, they can be reused and the price stays within the expected range. If they are rotten, wet or structurally compromised, they need to be replaced with exterior-grade plywood before any new covering goes on.
Decking replacement adds roughly £15 to £30 per square metre to the cost, depending on the thickness and the extent of the damage. On a roof where the covering has been leaking for some time, it is not unusual for a significant proportion of the deck to need replacing. A roofer cannot always tell from above exactly how much decking is affected until the old felt is stripped off, which is why experienced tradespeople explain this risk in advance rather than leaving homeowners surprised mid-job.
If your current roof has been leaking for more than a season, budget for some decking replacement as a realistic possibility rather than an unlikely extra.
The covering material itself makes a noticeable difference to the price. Built-up felt using traditional layers is the least expensive option and suits straightforward surfaces where budget is the priority. Torch-on modified bitumen felt sits in the middle range and offers better longevity than basic felt. EPDM rubber membrane is typically the most expensive to install on a domestic roof, though the material itself is durable and handles thermal movement well.
The price difference between a basic felt system and EPDM on a typical garage roof might be £200 to £400 in total. Over the longer service life of the EPDM, many homeowners find that difference is recovered in avoided maintenance and early failure, but it is a genuine choice rather than an obvious answer. The right system depends on your budget, how long you plan to stay in the property, and what the roof is over.
Many older flat roofs are cold-deck construction with minimal or no insulation above the joists. A roof replacement is a practical opportunity to upgrade to a warm-deck build-up, where insulation boards are laid above the deck and below the new membrane. This improves the thermal performance of the room below and reduces the risk of condensation forming within the roof structure.
Adding 80mm to 100mm of rigid insulation board adds roughly £20 to £40 per square metre to the cost of the job, depending on the product and the thickness. It is not compulsory, but on a heated habitable space such as a kitchen or living room extension, the running cost savings and improved comfort tend to make it worthwhile. On an unheated garage, many homeowners choose to skip it.
The cost of the covering itself is only part of the total. Flashings where the roof meets a wall, lead or aluminium trim at the perimeter edges, and dressed upstands at any vertical abutments all add to the material and labour cost. A roof with several wall junctions, a parapet, or multiple penetrations such as soil pipes or flue outlets will cost more to detail correctly than a simple flat slab with one straight gutter edge.
Cutting corners on flashings to reduce cost is a false economy. Wall junctions and perimeter edges are where most flat roof leaks originate, and a poorly dressed flashing on an otherwise well-installed roof will cause problems within a few years.
Most domestic flat roofs over extensions and garages are accessible from ladders without any special equipment. If your roof requires scaffolding because of its position, height, or proximity to a public footpath, that adds a hire and erection cost that can range from £300 to £600 or more for a simple independent scaffold lift. A roofer should factor this in during the survey rather than adding it as a surprise after the work starts.
Not every failing flat roof needs to be stripped and replaced. If the deck is sound and the covering is generally in reasonable condition apart from a localised failure at a joint or flashing, a targeted repair may be all that is needed. A repair on a small area of felt might cost £150 to £400 depending on the extent of the work and the access involved.
The honest caveat is that repairs on an ageing felt roof often buy a limited amount of time. If the rest of the covering is within a few years of the end of its life, spending money on repairs now and then replacing the whole roof again soon afterwards is not always the most cost-effective path. A straightforward way to think about it: if the roof is under ten years old and the failure is clearly localised, repair is likely the right call. If it is over fifteen years old and showing widespread crazing, blistering or multiple soft spots, a full replacement is usually better value.
When comparing prices for a flat roof job, make sure each quote covers the same scope. Ask specifically:
A lower headline figure that excludes decking replacement or uses a thinner specification can easily end up costing more once you account for what is missing. Price by scope, not by headline number.
Delaying a necessary flat roof replacement usually increases the final cost. Water that has been sitting on or under the covering will work into the deck, potentially requiring more boarding to be replaced. Damp that reaches the ceiling below can cause plasterwork damage and, in warm weather, mould. Acting when you first notice blistering, pooling water, or a damp patch on the ceiling tends to keep the job scope smaller than waiting another season.
We cover Elmswell and travel to nearby towns and villages, including Thetford, Bury St Edmunds, Brandon, and the surrounding area. For a flat roof survey and a clear breakdown of what your job is likely to cost, call Thetford Roofers and ask to arrange an inspection.
No obligation · We usually respond within 2 hours
Storm damage, active leak, damaged ridge - we aim to be on-site within 24 hours.
