What is due on your roof, and what is only old

A roof is a collection of parts that wear at different speeds, and on a three-decker some of those parts were fitted when the porches were, not when the roof was. Give it the year the house went up and what has been replaced since, and it will sort the parts by where each one stands.

This is a guide to where to look, not a finding. It sets ages against the service lives roofers generally expect. A pitched roof over a cold attic can outlast the range; a flat roof with a blocked scupper can fail years early. How it was built and how it drains matter more than the date.

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Enter the house, then mark the work

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

What has already been replaced?

Leave a row on Original if that part was never replaced, or if a prior owner may have done it and nothing came with the deed. Unknown is a fair answer on a building this age.

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

Nothing up here drains by accident. On a three-decker every drop is routed by something a person built. Which is why flashing, not shingle, is the item most worth knowing the age of.

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1 Ridge caps. The thinnest pieces up there, and the first to work loose over a hard winter.
2 The field. Slate on the older stock, shingle on the rest. They age on very different clocks.
3 Valleys. Leaf litter mats in them, and two slopes then drain through one line.
4 Flashing. Old masonry chimneys, and the porch roof that meets the wall three stories up.
5 The vent boot. Rubber that hardens and splits well ahead of the covering it sits in.
6 Eaves and ice dams. Where meltwater refreezes at the cold edge and backs up under the courses.

Why a new surface can be sitting on an old roof

When a roof is laid over the last one, which was normal practice here for decades, the surface is new and the layer beneath it is whatever was there. On a flat roof that may be two earlier membranes. The visible part resets; the part doing the work does not. That is why this page asks about the underlayment separately, and why on many buildings the honest answer is that no one knows.

Flashing works the same way. Sealing the old metal where a porch roof meets the wall is faster than rebuilding it, and it is done often enough that a roof from five years ago can be relying on flashing from the sixties. If you are told the roof is recent, ask whether the joints are.

Use this page

This tool may be copied or linked freely, crediting charlesriverroofing.com. If it helps a three-family owner in one of these cities decide whether they are buying time or buying a roof, it has done what it is for.

If you already have quotes, the comparison checklist lays three of them out row against row.