The complete guide to roofing and re-roofing

A repair fixes a defect. An overlay puts new covering over old battens and felt, which is cheaper and shorter-lived. A full replacement strips back to the rafters and renews membrane, battens, covering, leadwork and often the timber ends. Only the last of these resets the clock on your roof.

As a rule of thumb, if more than 20–25% of the covering has failed, or the felt is original bitumen from before the 1980s, replacement is usually better value over ten years.

Scaffolding is a fixed cost of roughly £1,200–£3,500 on a domestic property and is one of the most common exclusions in roofing quotations. Always check that it is included, for how many weeks, and who pays if the programme overruns.

Rear access, three-storey properties, terraced streets and pavement licences all add cost that has nothing to do with the roof itself.

Nobody knows the state of your rafter ends, wall plates and valley boards until the covering is off. A good quotation states a per-metre rate for timber replacement so you can price the risk. A poor one leaves it open as dayworks.

A contractor guarantee is worth exactly as much as the contractor's future existence. Manufacturer-backed and insurance-backed guarantees survive the contractor going out of business. Ask which one you are getting and request the documentation, not a line on an invoice.

Replacing more than 25% of a roof area triggers a building regulations requirement to upgrade insulation. Legitimate roofers will price this. Quotes that ignore it are cheaper because they are non-compliant.

• Is this a strip and re-cover, or an overlay of the existing roof?
• Is scaffolding included, and for how many weeks?
• What rate applies to replacing rotten timber, per metre?
• Are new battens, membrane and leadwork included?
• Will insulation be upgraded to meet building regulations?
• What guarantee is provided — contractor, manufacturer or insurance-backed?
• Are fascias, soffits and guttering inside or outside the price?
• Who removes and disposes of the old covering?

• Cold-call roofers who 'noticed slipped tiles from the road'.
• Cash discounts and pressure to start immediately.
• No scaffolding line in the quotation.
• A guarantee with no company registration or insurance backing.
• No mention of membrane, battens or leadwork on a full re-roof.