Diagnosis

What a roof looks like when it is telling you it is finished

A roof rarely fails suddenly. It gives four or five years of notice, in a specific order, and almost all of the signals are visible without setting foot on it.

From the ground, with binoculars

Lifted or flapping edge courses

Look along the eaves and up the rakes. Shingles that are no longer lying flat have lost their sealant bond, and in a market with this much wind that is the beginning of the end rather than a cosmetic complaint.

Missing tabs and bare patches

Obvious, and usually the result of a specific event. Note whether they are all on one slope, which is what a wind event looks like, or scattered everywhere, which is what an aged roof looks like.

Curling and cupping

Corners turning up, or the middle of the shingle dishing. This is the asphalt drying out, and it is usually worst on the sunniest slope and over the least ventilated part of the attic.

Dark patches with no granules

Bald spots where the mat is showing. The granules are the ultraviolet protection; once they are gone the shingle degrades quickly.

A wavy or dished plane

Sight along the roof line rather than at it. Waviness means the deck is moving — old layers, wet sheathing, or in the worst case framing. This one gets looked at properly rather than watched.

Rusted or lifted flashing

At chimneys, wall lines and skylights. Flashing is where roofs leak, and rust at a chimney is a five-year warning.

In the gutter

Granules in the gutter are the most misread signal in roofing. A new roof sheds loose granules for the first months and that is normal. What matters is a steady accumulation on an older roof, particularly a pile at the bottom of the downspout, and it matters more when you can see where they came from on the slope above.

• A layer of grit in the trough on a roof over fifteen years old is the shingle surface leaving.
• Granules concentrated below one slope point at that slope rather than at the whole roof.
• Pieces of shingle rather than granules mean the mat is breaking up, which is a different and later stage.
• Nothing at all in the gutter on a very old roof can mean the granules went years ago. Look at the slope, not just the trough.

From inside the attic

This is the part almost nobody does, and it is worth more than everything above. Go up on a bright day, with the lights off, and let your eyes adjust.

1. Look for daylight

   Thin lines of light at the deck seams are normal. Points of light at nail holes, or light around a penetration or at the eave, are not.

2. Look at the underside of the sheathing

   Dark staining, streaking below a nail, or a tide mark around a penetration all show water that has been in. Old stains are dry and matte; active ones are darker and often have a defined edge.

3. Feel the sheathing between the rafters

   Firm is right. Spongy is a deck problem and it changes the entire conversation, because soft sheathing does not hold a nail.

4. Check the nail points

   On a cold morning, frost on the nail points is condensation, which is a ventilation problem rather than a leak. Rusty nail points are the record of that happening for years.

5. Look at the insulation at the eaves

   If it is packed into the overhang with no gap above it, the intake ventilation is blocked, and that shortens the roof from underneath. See attic ventilation.

Signs that look worse than they are

The list that means call somebody

1. Water coming in, now, in any quantity.
2. A slope where the edge courses have lifted along its whole length.
3. Soft or spongy decking anywhere.
4. Multiple stains in different rooms.
5. A visible sag or wave in the roof plane.
6. Exposed mat over a significant area, or shingles breaking up rather than wearing.

Anything else on this page is a reason to get the roof documented while there is time to plan, not a reason to sign something this week. What an inspection produces is photographs slope by slope and a written condition report — see roof inspection.