How Much Does Sagging Roof Repair Cost in 2026? (UK)
Fixing a sagging or bowing roof in 2026 typically costs £1,500–£6,000 for a structural timber repair, though a minor localised fix can start at £350 and a badly deflected roof needing a full re-roof can reach £9,000–£18,000. The bill is driven by the cause — spreading rafters, a sagging purlin or rotten timbers — plus roof size, scaffolding and whether the covering has to come off.
How much is sagging roof repair in 2026?
Typical 2026 UK sagging roof repair costs:
- Minor / localised fix (re-bed ridge, replace a few battens, one sagging rafter) — £350–£900
- Rafter or purlin reinforcement (sistering, new purlin, tie-in) — £1,500–£4,500
- Structural repair with new timbers + partial re-cover — £4,500–£9,000
- Full re-roof where the deck is beyond saving — £9,000–£18,000+
Most homeowners with a genuinely sagging ridge spend £2,000–£5,000 once scaffolding and a partial re-cover are included. Catching it early — before rot spreads — is what keeps you in the repair band rather than the full re-roof band.
Sagging Roof Repair Cost by Severity
A dipping ridge line or a visible bow in the roof slope almost always traces back to one of four issues: rafter spread (feet kicking out at the wall plate), a sagging purlin, undersized or notched timbers, or water damage rotting the rafter feet. What you pay depends on how far it has progressed.
Cosmetic / localised fix — re-bed ridge, swap battens, prop one rafter
Suits a slight ridge dip caused by a loose ridge board or a couple of failed battens. The roofer re-beds the ridge tiles, replaces damaged battens and packs or sisters one rafter. Half-day to a day, often from a tower rather than full scaffold.
Rafter spread / purlin reinforcement
The classic cause of a bowing roof. The roofer or carpenter adds collar ties or a new steel/timber purlin, sisters weakened rafters and re-secures the wall plate to stop the spread. Covering usually stays on. Two to four days plus scaffold.
Structural repair + partial re-cover
Where rot has reached the rafter feet or a section of deck has failed. Tiles come off over the affected pitch, rotten timbers are cut out and replaced, new felt and battens go on and the tiles are relaid. Four days to a week.
Full re-roof — structure beyond economic repair
If widespread rot, historic overloading or an inadequate original design has left the whole roof deflected, replacing the covering and rebuilding the structure is more cost-effective than patch repairs. Includes new timbers, membrane, battens and covering.
What Actually Drives Your Bill
Two homes with an identical-looking dip in the ridge can be quoted thousands of pounds apart. These are the factors your roofer is really pricing.
1. Root cause
Rafter spread caught early is a £1,500–£3,000 job; the same spread left until the rafter feet rot can triple the bill because timber and covering both need replacing.
2. Whether the covering comes off
Reinforcement from inside the loft keeps costs low. As soon as tiles must be stripped and relaid you add £30–£70/m² and a skip.
3. Scaffolding & access
A standard two-storey scaffold adds £450–£1,100. Awkward access, three storeys or a road licence pushes this higher and is a fixed cost regardless of repair size.
4. Roof size & pitch
More rafters to reinforce and more m² to re-cover means more labour and material. A steep pitch is slower and needs more staging, adding roughly 10–20%.
5. Covering type
Concrete tiles are cheap to relay; natural slate, clay pantiles and stone are slower, more brittle and dearer to source, adding materially to any re-cover.
6. Structural engineer / Building Control
Adding a steel purlin or altering the structure may need a structural calculation (£300–£600) and Building Control sign-off (£300–£500).
Sagging Roof Repair Cost by UK Region
Based on a typical rafter/purlin reinforcement with a partial re-cover, including scaffold. Labour rates drive most of the regional spread.
Real Project: Bowing ridge on a 1930s semi, Reading
A homeowner noticed the ridge line dipping over their 1930s three-bed semi. Inspection showed rafter spread with two rotten rafter feet where a gutter had been leaking. The fix: new collar ties, a timber purlin, two sistered rafters and a partial re-cover of the affected pitch.
| Scaffold (two-storey, 3 weeks hire) | £850 |
| Carpentry — purlin, collars, 2 sistered rafters | £1,850 |
| Replacement timbers & fixings | £680 |
| Strip & relay 28m² (new membrane + battens) | £1,340 |
| Skip & disposal | £320 |
| Structural check & Building Control notice | £140 |
| Total | £5,180 |
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