Typical ranges by material
These are the ranges most manufacturers and roofing trade groups describe. A roof can fall short of them or outlast them, so treat them as a starting point for planning, not a promise.
- Three-tab asphalt shingles: roughly 15 to 25 years. Common on houses built from the 1960s to the 1990s.
- Architectural (laminated) asphalt shingles: roughly 20 to 30 years. The usual choice for replacements today.
- Slate: often 75 years or more for the stone itself. The nails and flashing usually give out first.
- Standing-seam metal: often 40 years or more, longer with good paint systems.
- Flat roofs on rowhouses (modified bitumen, EPDM, TPO): roughly 15 to 30 years depending on the membrane and drainage.
See also: Asphalt shingle roofs · Slate and metal roofs
What wears roofs out around Harrisburg
Central Pennsylvania roofs face all four seasons. Winters swing above and below freezing many times, so water that gets into a crack freezes, expands and widens it. Summer sun bakes south- and west-facing slopes, which is why those sides of a roof usually lose granules and curl first. Spring and summer thunderstorms bring wind and, some years, hail.
Houses along the Susquehanna and in low spots near creeks also see more damp mornings and shade, which feeds moss and algae on north-facing slopes. Algae streaks are mostly cosmetic; thick moss holds water against the shingles and is worth dealing with.
What the house itself does to a roof
Two houses with the same shingles can see very different lifespans. The biggest difference is usually the attic. A hot, poorly vented attic cooks shingles from below in summer and causes ice dams and condensation in winter. See attic ventilation.
- Ventilation and insulation in the attic.
- How many layers are already on the roof. A second layer traps heat and adds weight.
- Flashing around chimneys, walls and skylights, which often fails before the shingles do.
- Overhanging trees, which drop debris, hold moisture and scrape the surface in wind.
How to tell how old your roof is
- 1Look through closing papers or the seller's disclosure from when you bought the house.
- 2Check the attic or garage for a leftover shingle bundle with a date or product name.
- 3Ask neighbors on the same street, since many blocks were reroofed around the same time.
- 4Ask your municipality whether it keeps permit records for re-roofing, if it requires permits.
The practical rule
If an asphalt roof is past 20 years and showing curling, bare patches or leaks in more than one place, start planning a replacement before winter rather than after it.
Questions
+Does a lighter or darker shingle color change how long it lasts?
Slightly. Darker shingles run hotter in summer sun. Ventilation and installation quality matter far more than color.
+Can a new layer of shingles go over the old ones in Pennsylvania?
The building code generally allows up to two layers of asphalt shingles if the deck and old roof are in suitable condition, but a full tear-off lets the roofer see and fix the deck and flashing. Many homeowners choose a tear-off for that reason.
+Does a roof last longer if it is cleaned regularly?
Keeping gutters clear and removing thick moss helps. Pressure washing does the opposite: it strips the protective granules off asphalt shingles.