Roof Repair or Replacement: Making the Right Call

The signs worth acting on

Inspect from ground level with binoculars, and from inside the loft on a bright day with the light off. Daylight through the roof, damp or blackened timbers, and sagging between rafters all tell you more than a view from the pavement.

Slipped, cracked or missing tiles and slates · A visible dip or sag in the roof line · Failed or cracked mortar at ridge, hip and verge · Nail sickness on older slate roofs: slates slipping with no obvious damage · Damp, mould or daylight visible in the loft · Granules from flat roof felt collecting in the gutters · Blocked or sagging gutters causing water to run down the wall

Repair or replace: the honest test

Repair is the right answer when the covering is generally sound, the battens and felt beneath it are in reasonable condition, and the failure is localised, such as storm damage or a run of slipped tiles.

Replacement becomes the sensible answer when more than roughly a fifth of the covering has failed, when the battens are rotten or the roof has no underfelt at all, when the same area has been patched repeatedly, or when the structure has begun to deflect. At that point money spent on patching is money spent twice.

Indicative UK roofing costs

Costs below are typical South East ranges for 2026 on an average three-bedroom semi-detached property, including scaffolding unless stated.

Indicative roofing costs, South East England (2026). Work | Indicative range | Expected life. Replace a handful of slipped tiles — £150 – £400 — Matches remaining roof life; Re-bed ridge tiles — £500 – £1,200 — 10 – 20 years; Repoint verges and re-flash a chimney — £600 – £1,500 — 15 – 25 years; Full re-roof, concrete tile — £6,000 – £12,000 — 40 – 60 years; Full re-roof, clay tile — £9,000 – £16,000 — 60 – 100 years; Full re-roof, natural slate — £12,000 – £22,000 — 80 – 100+ years; Flat roof, EPDM rubber, per m² — £90 – £140 — 30 – 50 years; Flat roof, GRP fibreglass, per m² — £100 – £160 — 25 – 30 years; Flat roof, torch-on felt, per m² — £70 – £110 — 15 – 25 years; Scaffolding for a semi — £800 – £2,000 — Per hire period

What a proper re-roof includes

A full re-roof is not a tile swap. The covering and battens come off, the structure is inspected and any rotten timber replaced, a modern breathable membrane goes down, new treated battens are fixed, and the covering is laid with correct fixings, ventilation at eaves and ridge, and new lead or proprietary flashings at every abutment.

Ventilation is the item most often skimped. A well-sealed modern roof with no eaves or ridge ventilation traps moisture in the loft and rots the timbers it was meant to protect.

Flat roofs, and why felt keeps failing

Most flat roof problems are not the covering, they are the falls. Water that cannot reach an outlet sits, and standing water will find its way through any joint eventually. Any flat roof rebuild should correct the falls with tapered insulation or firrings before a new membrane goes anywhere near it.

Where the deck is being rebuilt, single-ply EPDM in one continuous sheet removes the seams that felt relies on, which is why it outlasts felt by decades on a comparable roof.

Regulations, warranties and insurance

Replacing more than half of a roof's area is a building control matter in England and typically triggers a requirement to upgrade insulation to current standards. That is a benefit, not a penalty, but it needs to be in the quote rather than discovered later.

Storm damage is normally covered by buildings insurance; gradual wear and tear is not. Photograph damage promptly, keep the old materials where practical, and notify your insurer before work begins.

Frequently asked questions

How long should a roof last?

Concrete tiles around forty to sixty years, clay longer, natural slate potentially a century. Felt flat roofs are the short-lived exception at fifteen to twenty-five years, and modern rubber membranes considerably longer.

Can a roof be replaced in winter?

Yes, in stages and with temporary protection, though wet and windy weather causes delays. Spring and early autumn are easier and generally cheaper because demand and delays are lower.

Do I need planning permission to re-roof?

Usually not for a like-for-like replacement, but a change of material or profile in a conservation area or on a listed building normally does need consent. Building regulations apply where a substantial area is renewed.

Is a roof coating a real alternative to re-roofing?

Rarely. Coatings can extend the life of a sound roof, but sprayed foam in particular can trap moisture and has caused mortgage difficulties for owners. Treat any coating pitched as a cheap alternative to a re-roof with caution.