How long does a roof last?

Rarely does a whole roof fail at once. More often, one component gives up early and lets water reach everything else. Mortar on ridges and chimneys cracks with frost, nails and clips corrode, underlay perishes, and lead splits where it has been worked too hard. The covering you can see from the street may still look fine while the parts underneath are failing.

That is why no honest roofer will promise a fixed number of years. What we can do is look at each part, tell you how it is doing, and explain what is likely to need attention first.

Good natural slate is extremely durable, and on many old Scottish houses the slates themselves are still sound. What usually ends the life of a slate roof is the fixing: iron nails rust through, slates slip, and the roof gradually loses its grip. Frost damage and delamination affect poorer slates, and old repairs with mismatched pieces can create weak spots.

When a slate roof is stripped, sound slates can often be reused, combined with new fixings, battens and underlay. Our guide to slate vs tile roofs explains more about how the two materials age.

Concrete tiles are tough but their surface slowly wears, so they can become rougher, hold moss and absorb more water as the years go by. Clay tiles tend to keep their colour but can be brittle. On both, ridges, verges and valleys are usually the first places to need work, especially where they are bedded in mortar.

Tile roofs on many post-war and modern homes are now reaching the age where fixings, underlay and ridges need a proper look, even if the tiles appear sound.

A flat roof has a harder life than a pitched one because water sits on it for longer. Its lifespan depends heavily on the deck below, the falls that carry water away, and the quality of the edges and upstands. Poor drainage, foot traffic and repeated patching all shorten it.

If a flat roof is at the end of its life, our guide to flat roof replacement cost explains what decides the price of renewing it.

Beneath the covering sit the layers that hold it in place and act as a second line of defence. Old bituminous felt becomes brittle and tears; battens can rot if water has been getting in; nails corrode, particularly in salty coastal air. These parts are hidden, which is why a look in the loft tells us a lot. Daylight through the roof, damp timbers or torn felt are clear signs.

Where the roof meets a chimney, a wall or another slope, the junctions are sealed with lead or mortar. These details are worked hard by weather and movement, and many leaks start here long before the main covering fails. Keeping pointing, flaunching and flashings in good order can add years to a roof that is otherwise sound.

From the ground, look for slates or tiles slipping in several places, a sagging line along the ridge, heavy moss, or debris regularly appearing in gutters. Inside, watch for damp patches that return after heavy rain, staining on rafters, or daylight visible in the loft.

A single one of these is usually a repair. Several together, across more than one slope, often mean the roof as a whole is tiring.

There are really three choices. A repair puts right a local fault. An overhaul tackles a whole area, such as re-fixing a slope or renewing ridges and lead, to buy many more years. A replacement strips the roof back and starts again with new underlay, battens and covering. Our pages on new roofs and roof replacements explain what the last option involves.

If you are weighing up replacement, our guide to how long a new roof takes covers what to expect while the work is under way. Rowan Roofing is family-run and based in Cardenden; we survey before quoting and put our advice in writing. Call 07508 571291 to arrange a visit.