The International Association of Certified Home Inspectors (InterNACHI) publishes standard life-expectancy estimates that inspectors use when they report on a home. They're a fair starting point, with InterNACHI's own caveat: the life of a roof depends on local weather, building design, material quality and maintenance.
Average lifespan by roofing material
Years of expected life. Source: InterNACHI Standard Estimated Life Expectancy Chart. Lighter bars show the range.
Most Westchester homes have asphalt shingle roofs. The older 3-tab style is rated for about 20 years and the thicker architectural (laminated) style for about 30. Many older homes, including a good share of Scarsdale's 1910s to 1930s Tudors, still have original slate that can outlast several asphalt roofs, as long as the flashing and fasteners are kept up.
What shortens a roof's life in Westchester
Freeze, thaw and ice dams
Westchester averages 25 to 50 inches of snow a year and several days of freezing rain. When heat from the house melts snow higher on the roof, the water refreezes at the eaves and backs up under the shingles. Repeated every winter, that wears out eaves, gutters and decking long before the rest of the roof.
Poor attic ventilation
GAF's technical guidance warns that excess attic heat and moisture can damage roofing products and the structure under them. A hot attic bakes shingles from below in summer, and a damp one rots the deck in winter. Both GAF and Owens Corning exclude ventilation-related damage from their warranties. More on ventilation.
Trees, shade and debris
Much of Westchester is wooded. Leaves and needles pack into valleys and gutters and hold water against the roof. The National Roofing Contractors Association tells homeowners to keep valleys, gutters and drains clear for exactly this reason. Shaded, north-facing slopes also grow algae and moss. Algae-resistant shingles prevent the black streaks, and trimming overhanging limbs prevents most of the rest.
Installation quality
Nailing pattern, starter strips, flashing at walls and chimneys, and valley construction all decide whether a roof reaches its rated life. Neither manufacturer's standard warranty covers installation errors, which is why the enhanced warranties that do are worth having.
Wind
Nor'easters and tropical storms test every edge of a roof. In March 2018, back-to-back nor'easters brought 50 to 80 mph gusts to the region. Shingles installed with the manufacturer's high-wind details hold up far better than those nailed to the minimum.
A “lifetime” warranty isn't a lifetime roof
GAF and Owens Corning both sell architectural shingles with a “lifetime” limited warranty. In both cases, lifetime means for as long as you own the home. It doesn't mean the shingles are expected to last that long. What matters is:
- The non-prorated period. On a standard warranty, full coverage lasts 10 years. After that, the manufacturer pays a declining share.
- What's excluded. Installation errors, inadequate ventilation and ice damming are excluded from standard coverage.
- Transfer limits. If you sell the house after the non-prorated period, the next owner's coverage shrinks to a short period.
Enhanced system warranties, registered by certified contractors, extend the non-prorated period to 50 years, and the top tiers add workmanship coverage. See roof warranties compared.
How to get the most life out of a roof
- Have the roof inspected twice a year, in spring and fall, as the NRCA recommends, and after major storms.
- Keep gutters, valleys and downspouts clear, especially after leaf drop.
- Trim branches that touch or overhang the roof.
- Make sure bathroom and kitchen fans vent outdoors, not into the attic.
- Fix small problems like a lifted shingle, a cracked pipe boot or loose flashing before water reaches the deck.
- When it's time to replace, fix the ventilation and add ice and water barrier at the eaves and valleys.