What is due on your roof, and what has time left

The parts of a roof wear out on separate schedules, and on a house that shares a wall some of those parts were last touched by a neighbor's contractor. Enter when the house was built and what has been replaced since, and it will show where each part stands.

This points you at what to look at. It does not diagnose anything. It compares ages to the service lives roofers generally expect. Slate can run far past the range; a shallow porch roof under shingle can fall well short of it. Pitch, exposure and how it was installed count for more than the year.

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Set the house, then mark what has been replaced

When was the house built? What is on the roof now?

What has already been replaced?

Keep a row on Original if that part has never been replaced, or if the previous owner may have done it and left no paperwork. On a house this age, unknown is a common and honest answer.

Roof covering Flashing at walls, valleys and penetrations Underlayment and ice-and-water shield Gutters and downspouts Attic ventilation Skylights (if you have them) Chimney crown, cap and masonry (if you have them) Fascia and soffit Siding or exterior cladding Window seals

An old roof rarely gives out in the field. It gives out at the joints and the edges. Which is why flashing, not shingle, is the item most worth knowing the age of.

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1 Ridge caps. Thin, fully exposed, and usually the first course to let go.
2 The field. Slate on the older rows, shingle on the rest, each on its own clock.
3 Valleys. Two slopes emptying through one line, with litter holding the water there.
4 Flashing. Old masonry, and the party wall a rowhouse shares with the house next door.
5 The vent boot. A small rubber part with a far shorter life than the roof it sits in.
6 Eaves. Where the porch roof ties into the wall, and where backed-up water gets in.

Why a roof can be older than its shingles

A roof laid over the last one leaves the earlier underlayment, and sometimes the earlier slate, in place beneath the new surface. What you see resets; what keeps water out does not. This is why the page asks about underlayment on its own line, and why on many of these houses the truthful answer is that no one knows when the deck was last exposed.

Flashing follows the same logic, and on a rowhouse it is worse, because the flashing at the party wall was last touched by whichever house re-roofed most recently. A roof from five years ago can be relying on metal from the seventies on its shared side. If someone tells you the roof is recent, ask about the wall.

Use this page

Copy or link to this freely, crediting delriverroofing.com. If it helps someone on a block of twins or rowhouses tell a flashing problem from a roof problem, it has earned its place.

Quotes already in hand? The comparison grid sets up to three of them side by side, line for line.