When Does a Roof Need Replacing Rather Than Repairing?

Most roofs give plenty of warning before they hit end-of-life. Any two of the following in combination usually mean replacement is better value than continued repair.

Failing underlay. If daylight is visible through the felt in multiple areas, or the underlay is brittle and torn, the roof is only as good as the tiles themselves.

Widespread nail-sickness. When slate fixings fail across a whole elevation, individual repairs become a rolling programme — a re-roof solves it in one visit.

Sagging structure. Ridge dip, rafter deflection or a wall-plate that's rotted through means opening up the roof anyway. Combine that with a re-cover and it's usually the economic choice.

End-of-life covering. Natural slate can last a century; concrete tile is closer to 40–60 years. If the covering is beyond service life, matching a repair is a temporary fix.

Repair economics. If a serious repair would cost more than a third of a re-roof, it usually pays to re-roof once and be done for a generation.

A drone survey plus a loft inspection gives you the objective picture. From there, a written quote for both options lets you decide with numbers.