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    Flat Roof Replacement Cost in the UK

    Flat roofs are common on UK extensions, garages, porches, and some modern properties. When they start to fail, replacement is often more cost-effective than ongoing repairs. Here's a comprehensive guide to flat roof replacement costs in 2026.

    Flat Roof Replacement Costs by Material

    Material Cost Per m² Lifespan Best For
    3-Layer Felt £50 – £70 10–20 years Budget option
    EPDM Rubber £80 – £120 25–50 years Best all-rounder
    GRP Fibreglass £90 – £130 25–40 years Seamless, walkable
    Single-Ply (PVC/TPO) £70 – £100 20–30 years Larger flat roofs
    Lead £120 – £180 50–100+ years Premium/heritage

    Total Cost by Roof Size

    Roof Size Felt EPDM GRP
    10 m² (porch) £500 – £700 £800 – £1,200 £900 – £1,300
    20 m² (garage) £1,000 – £1,400 £1,600 – £2,400 £1,800 – £2,600
    30 m² (extension) £1,500 – £2,100 £2,400 – £3,600 £2,700 – £3,900
    50 m² (large extension) £2,500 – £3,500 £4,000 – £6,000 £4,500 – £6,500

    EPDM vs GRP: Which Should You Choose?

    These are the two most popular modern flat roof materials. Here's how they compare:

    • EPDM is slightly cheaper and extremely durable. It's a single rubber sheet that's bonded to the roof deck, making it watertight with no joins.
    • GRP provides a seamless, hard-wearing finish that can be walked on. It's ideal for balconies or roof terraces but costs a bit more.
    • Both offer excellent lifespans of 25+ years when properly installed.

    Signs Your Flat Roof Needs Replacing

    • Ponding water that doesn't drain within 48 hours
    • Visible cracks, splits, or blistering in the surface
    • Water stains on ceilings below the flat roof
    • The felt is cracking, curling, or coming away
    • Multiple repair patches that keep failing
    • The roof is over 15 years old (for felt)

    Flat Roof Repair Cost UK

    If the damage is small, a flat roof repair typically costs £200–£600 for a localised patch and £600–£1,200 for larger sections of failed felt or EPDM. Anything over ~40% of the roof area is usually better value as a full replacement. See our repair vs replacement guide for the full cost-benefit comparison.

    Garage Flat Roof Replacement Cost

    A typical single-garage flat roof costs £800–£2,000 to replace, and a double garage £1,200–£3,500 depending on material. See our dedicated garage roof replacement cost guide for a full breakdown by size and material.

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