How Do I Know When an Old Roof Needs Replacing?

There is a long grey zone between a roof that needs a repair and a roof that needs replacing, and a lot of money gets wasted in it — in both directions. People spend on repeated patch repairs to a roof that is finished, and people replace roofs that had a decade left.

The signs below are the ones worth acting on. They apply to any older property, and they apply particularly to the Victorian and Edwardian housing that makes up so much of Altrincham, where the original covering is often slate and the original fixings are long past their working life.

What You Can See From the Ground

Slipped or missing slates and tiles, repeatedly

The pattern matters more than the count. A couple of slates down after a storm is weather. Slates coming down in ones and twos across the whole roof, in different places, over several years, is nail fatigue — the fixings corroding through. Once that process is general across a roof there is no repair that stops it, because every remaining slate is on the same clock.

A dipped ridge or a wave in the slope

Sight along the ridge from an angle. A visible sag, or a slope that is no longer flat, points at the structure rather than the covering. Some of it is historic movement that stopped long ago. Some is live. Telling those apart needs a look at the timbers from inside.

Vegetation and heavy moss

Moss on a north slope is normal in this climate and is not in itself a reason to replace anything. Moss thick enough to hold water against the covering, block gutters and lift tile edges is doing damage. Plants actually rooted in a valley or behind a chimney mean debris has been sitting there long enough to form soil, which means water has been sitting there too.

Cracked and missing mortar at ridges and verges

Look along the ridge line and the gable edges. Crumbling mortar, gaps, or a ridge tile sitting proud of its neighbours all admit water. On its own this is a repair. Combined with other signs it is part of the picture.

Rusted or failing flashings

Look where the roof meets a chimney, a wall or a dormer. Lead that has split, lifted or been repaired with mastic is a common source of damp that gets blamed on the covering.

What the Loft Tells You

This is the most useful ten minutes you can spend, and it costs nothing. Go up on a bright day and take a torch.

• Daylight. Pinpricks of light through the covering mean gaps. A few at the eaves may be ventilation. Light visible across the roof means the covering and underlay are both compromised.
• The underlay. Old bitumen felt goes brittle and tears, particularly where it drapes between rafters and at the eaves. Torn underlay is the difference between a slipped slate being an inconvenience and being a leak.
• Damp staining on the rafters. Dark patches, particularly near the chimney, at valleys or along the eaves. Feel whether they are wet now or historic.
• Soft or crumbling timber. Press the rafter ends near the wall plate. Long-term water from a failed gutter shows up there first.
• Sagging between rafters. If the underlay hangs heavy or the battens dip, water has been getting in for a while.
• Insulation. Damp, flattened or displaced insulation tells you both that water has been present and that the roof is probably nowhere near current thermal standards.

The Signals That Usually Mean Replacement Rather Than Repair

Any one of these on its own may not settle it. Two or three together generally do.

• Slates or tiles slipping generally across the roof rather than in one area
• Underlay torn or perished over most of the roof
• Battens splitting or rotten where they can be seen
• Repairs needed more than once a year, in different places each time
• Widespread delamination — slates flaking into layers — or tiles crumbling at the edges and losing their surface
• Damp appearing inside the house in more than one place
• Structural deflection that is still moving

The Signals That Do Not Mean Replacement

In fairness to the roof, several alarming-looking things are not terminal:

• A single slipped slate after a storm
• Moss on a shaded slope, absent gutter blockage
• A stained ceiling directly under a chimney — often a flashing or a flaunching problem, not the covering
• Gutters overflowing, which is a gutter problem
• A cracked ridge tile or two

A roofer who inspects any of those and immediately recommends a full re-roof is worth a second opinion.

Getting a Straight Answer

When Apex Roofing looks at a roof in Altrincham, we look at the outside and the loft, and we tell you which of the two categories above you are in. If a roof has ten years left and needs a chimney flashing renewed, that is what we will quote for.

If it has reached the end, we will show you why, so the decision is yours and made on evidence rather than on a sales pitch.

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