How Do I Know When My Roof Needs Replacing?

Almost everyone assessing their own roof does the same thing: stands in the street and looks up. That is one source of evidence and it is not the best one.

A roof reaching the end of its life leaves traces in four places. Taken together they give a much clearer picture than any of them alone — and the loft, which hardly anyone checks, is usually the most informative of the four.

One: On the Roof

Slipped or missing units — and the pattern

The pattern matters far more than the number. A couple down after a gale is weather. Units coming down in ones and twos across the whole roof, in different places, over several years, with nothing to explain them, is general failure of the fixings. Every nail on that roof is the same age and in the same condition, so once they start going they keep going.

A dipped ridge or a wave in a slope

Sight along the ridge at a low angle. A visible sag points at the structure rather than the covering. Some of it is old movement that settled long ago and some is live, and telling those apart needs a look at the timbers from inside.

The condition of the units themselves

• Slates flaking, splitting into layers, or gone soft and thin
• Concrete tiles crumbling or flaking at the exposed lower edge — frost damage
• Widespread breakage rather than the odd cracked unit

On concrete tile there is a useful distinction here. Fading to grey is cosmetic — the colour is a surface pigment that weathers away, and a faded roof is not a failing roof. Crumbling and flaking at the tile edge is not cosmetic, because it means the surface has broken down and frost is getting into the material.

The junctions

Cracked or missing mortar at ridges and verges. Lead that has split, lifted, or been patched with mastic. These are small in area and disproportionately visible, and on older property with multiple chimney stacks there is a lot of junction to inspect.

Vegetation

Moss on a shaded slope is normal in this climate and is not on its own a reason to do anything. Moss thick enough to hold water against the covering and block the gutters is doing harm. Plants actually rooted in a valley mean debris has been sitting there long enough to form soil, which means water has been sitting there too.

Two: In the Loft

Ten minutes, a torch, a bright day. This is the highest-value inspection available to a homeowner and it costs nothing.

• Daylight through the covering. A few pinpricks at the eaves may be ventilation. Light visible across the roof means covering and underlay are both compromised.
• The underlay. Old bitumen felt goes brittle and tears, especially at the eaves. Torn underlay is the difference between a slipped unit being an inconvenience and being a leak.
• Damp staining on rafters. Feel whether it is wet now or historic.
• Rafter ends at the wall plate. Press them. This is the first place to soften, because it is where a failing gutter deposits water.
• Battens. Split along the nail line, or dark and soft.
• Insulation. Damp, flattened, thin or absent — and whether it is blocking the eaves ventilation path.

Three: Inside the House

The source of evidence almost nobody counts as roof evidence, and it is often the first thing anyone actually notices.

• Ceiling stains, and how many rooms. One stain under a chimney is probably a flashing. Marks in two or three unrelated rooms suggest something general.
• Damp on a chimney breast. Usually the lead or the flaunching at the stack rather than the covering. Worth diagnosing separately — it is often a repair.
• Peeling paint or bubbling plaster on upstairs ceilings and the tops of walls.
• A musty smell in upstairs rooms, which can mean sustained low-level damp rather than a dramatic leak.
• A sagging or discoloured ceiling in one area — water sitting above it.

The count is the diagnostic. One location with an obvious source above it is a repair. Several unrelated locations point at the covering or the underlay generally.

Four: In the Heating

The least obvious source, and a real one on older property.

• Upstairs rooms noticeably harder to heat than downstairs
• Snow melting off your roof faster than off neighbouring roofs — a genuinely useful indicator that heat is escaping through it
• Cold draughts at the top of the stairs
• Insulation visibly thin, flattened, or laid over old damp

This does not tell you the covering is finished. What it tells you is that a replacement would deliver something a repair never will, because the thermal upgrade attaches to the replacement and not to any amount of patching.

Putting the Four Together

One column of evidence is suggestive. Two or three columns agreeing is about as clear as this gets without stripping the roof.

The Signs 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 with the gutters running clear
• A stained ceiling directly under a chimney — usually a flashing
• Overflowing gutters, which is a gutter problem
• A cracked ridge tile or two
• Concrete tiles faded to grey — cosmetic, not structural
• Condensation in the loft in cold weather, which is a ventilation question

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

The Regulations, in Brief

Two systems, and they are separate. Planning: a like-for-like re-roof does not materially affect the external appearance of a building, so under section 55 of the Town and Country Planning Act 1990 it is not development at all and needs no permission. A visible change of covering can be a different matter, particularly inside a conservation area.

Building regulations: where more than 50% of the roof's surface area is renewed, or the work forms part of a major renovation, regulation 23 of the Building Regulations 2010 requires the roof to be brought up to current thermal standards so far as that is technically, functionally and economically feasible. A patch repair does not trigger it, and neither does a roof over unheated space such as a detached garage. The work is signed off through building control or by a roofer registered under a competent person scheme, and you should receive a certificate.

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