What on your roof is worn, and what is merely old

The parts of a roof do not age together, and on a house with slate that is more true than usual: the slate may have fifty years left while the copper under it has none. Enter when the house was built and what has been replaced, and it will sort the parts by where each one stands.

This is a starting point for looking, not a verdict on the roof. It compares ages to the service lives the trade generally expects. Quarry slate can outlive the range by decades; the flashing beneath it rarely does. What the roof is made of and how it was fitted matter more than the year.

This runs on your screen and nowhere else. Nothing is sent and nothing is kept.

Enter the house, then mark the work done

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

What has already been replaced?

Leave a row at Original if that part was never replaced, or if a previous owner may have done it and left nothing on paper. On a house this age, not knowing is the usual state of affairs.

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

Slate does not fail the way shingle fails. On old housing it gives out where two centuries meet. Which is why flashing, not shingle, is the item most worth knowing the age of.

Tap to enlarge

1 The ridge. The highest course, and on slate the one most often reset by hand.
2 The field. Quarry slate on the old houses, asphalt on everything since. Two very different clocks.
3 Valleys. Where leaf litter settles, and where a slate roof usually ends its life.
4 Wall flashing. The party wall of a row or twin, rising through a roof two houses share.
5 Penetrations. Holes cut on purpose. When access is awkward they get sealed instead of rebuilt.
6 The overhang. Where meltwater from a warm attic reaches cold framing and stops.

Why old slate can be the youngest part of the roof

When a roof is covered over rather than stripped, the surface is new and everything beneath it is whatever was there. On a slate roof that has been patched for a century the underlayment may be the original felt. The visible part resets; the working part does not. That is why this page asks about underlayment separately, and why on many of these houses the honest answer is that nobody knows.

Flashing is the same story with higher stakes. Copper valleys and step flashing that were sealed rather than rebuilt on the last job may be a hundred years old under a ten-year-old repair. If someone says the roof is sound, the useful question is whether they mean the slate or the metal.

Use this page

Reproduce or link to this freely, crediting kittatinnyroofing.com. If it helps someone in Allentown or Reading understand that the slate can stay and the copper cannot, or the reverse, it has done its work.

If you are holding quotes already, the comparison checklist lines up three of them, row against row.