No table can say that your roof needs replacing; an inspection on the roof can. What public records can tell you is how long roofs of each kind are expected to last, how old the houses around you are, and, often, when your own roof was last replaced.
How long roofs last
HUD's table of estimated useful life, used to plan capital spending on housing, gives:
| Roof covering | Useful life (years) |
|---|---|
| EPDM or TPO single-ply membrane | 15 |
| Built-up roof, with gravel | 20 |
| Built-up roof, without gravel | 10 |
| Asphalt shingles | 20 |
| Wood (cedar) shingles | 25 |
| Clay or concrete tile | 60 |
| Metal | 50 |
| Slate | 75 |
A "30-year" shingle or a 20-year membrane is a warranty term, not a measured life. Sun is the main enemy of a flat roof: the City's Rowhouse Manual calls sunlight "the worst enemy of roofing materials."
How old the houses are
Philadelphia County's median year built is 1949, and 39.9% of its homes date from 1939 or earlier (ACS 2020–2024). In 19134 the share is 71.6%; in the Far Northeast ZIP codes it is under 5%. A house from the 1920s is on its third, fourth or fifth roof. That is a likelihood, not a diagnosis: the Census Bureau does not record when roofs were replaced. Each ZIP code page shows the decades homes there were built.
When your roof was last replaced
Since 2015 a roof covering replacement in Philadelphia has been filed as an EZ permit, and the City publishes every one. The roof permit lookup searches 13,120 of them by address. If your house shows a permit from 2019, you know the roof's age; if it shows none, the work may predate the EZ type, have been filed differently, or never have been permitted. Sellers' disclosures and the previous owner's papers are the other places to look.
What an inspection looks at
The City's rules name the conditions that matter, and a contractor's inspection works through the same list:
- Layers. How many coverings are on the roof now. Two or more mean a full tear-off (EZ standard).
- Condition of the covering. Whether it is "water-damaged or deteriorated," the standard's words for a roof that cannot be covered over.
- Drainage. Water that stands on a flat roof for days means the quarter-inch-per-foot slope the code requires (IRC 2021 R905) or the drain has failed.
- The deck. Soft or rotted boards; the share that needs replacing decides whether the job stays an EZ permit (10% of the sheathing).
- Flashing and drain parts. Rusted or damaged flashing, edgings, drain outlets and collars, which the standard does not allow to be reused.
When the code decides
Two existing layers, a deteriorated roof, or slate mean the next roof starts with a full tear-off under the City's EZ standard; a third layer is not allowed. See tear-off or roof-over.
A single leak on a roof with years of life left is usually a repair, which this line does not handle. If you are not sure which you are facing, read repair or replace.