What damages roofs most in Denver is wind and hail, followed by sun, flashing mistakes and snow, and you defend against each one differently. Wind and hail cause the sudden damage: the National Weather Service says winds of 60 to near 100 mph occur in and near the foothills, including Denver, and the May 8, 2017 storm dropped hail up to baseball size on Golden, Lakewood, Wheat Ridge and northwest Denver. Sun and snow work slowly, aging shingles and loading the eaves. Flashing mistakes are the one threat that comes from people, not weather. Each has a specific defense.
1. Wind
Denver’s worst winds come downhill. The NWS Denver/Boulder office says chinook and bora winds descending the foothills can exceed 100 mph in extreme cases, and upper-level winds are much stronger in winter than in summer. Wind lifts shingles at the edges and ridge first, breaks the seal and creases or tears them off.
Defense. Denver sets minimum shingle wind ratings by location (115 mph east of Federal, 125 mph to Sheridan, 140 mph to Kipling), requires shingles labeled to ASTM D 7158, and requires at least four nails per shingle strip or the manufacturer’s pattern. Correctly set nails matter: overdriven nails cut through the shingle and let it pull free in wind. Our article on high winds in Denver covers what to check after a windstorm.
2. Hail
Summer thunderstorms bring hail that damages a roof in minutes, not years. On May 8, 2017, the NWS reported hail up to baseball size in Golden, Lakewood, Wheat Ridge and northwest Denver. Our May 8, 2017 Denver hailstorm article covers that storm.
Defense. No roof is hail-proof; we have seen tile, metal, wood and asphalt all damaged. Class 4 impact-rated shingles, tested under UL 2218 by dropping a 2-inch steel ball from 20 feet onto the same spot twice without cracking the shingle, resist hail far better than standard shingles. Stone-coated steel and some metal systems also carry Class 4 ratings. Our Class 4 shingle comparisons explain the options.
3. Sun
Ultraviolet light starts breaking down the asphalt in shingles from the day they are installed, and Denver’s elevation and sunny climate add exposure. As shingles age they lose flexibility, and brittle shingles are damaged by smaller hail than new ones. In our experience, a 1-inch hailstone that a new shingle shrugs off can bruise a lightweight shingle that is ten or more years old.
Defense. Choose a heavier, better-rated shingle when you replace, keep the attic ventilated so the deck does not bake, and have older roofs inspected after any hail.
4. Flashing mistakes
Flashing turns water at walls, chimneys, skylights and valleys. A small error at the wrong spot, where a lot of water funnels, can put a stream into the house. Wind-driven rain finds those errors first. The photo above shows the kind of damage a failed skylight seal leaves inside.
Defense. Denver’s checklist spells out the details a good installer follows: step flashing at least 4 by 4 inches per shingle, counterflashed and sealed; kick-out flashing at the bottom of sidewalls to direct water away from the wall; flashing replaced where rusted or damaged; and a cricket behind chimneys and other projections wider than 30 inches. Ask how your roofer flashes walls and chimneys, and whether their installers are trained.
5. Snow and ice
Denver homes are designed for a 35 psf ground snow load. Snow that melts on a warm roof and refreezes at the eaves builds ice that can back water under shingles, and heavy, sliding snow tears gutters and edges.
Defense. Good attic ventilation and insulation keep the roof deck cold and even. Denver does not require ice and water shield at the eaves, but it is worth asking for on homes with a history of ice dams.
When to call
If you can see missing shingles, find granules or shingle pieces in the yard, or have a stain on the ceiling, it is time for an inspection; signs you need a roofer in Denver lists the rest. If you are choosing a new roof with these threats in mind, see Denver’s most popular roof types, planning a new roof in Denver and, for heavy tile, clay tile in Denver.
Defend your roof with us
Integrity Roofing and Painting is veteran-owned and family-run since 1990, an Owens Corning Platinum Preferred contractor with 650+ Google reviews. Call our Denver-area office at (303) 209-0152, book a free Denver roof inspection, or see Denver storm damage repair.
Sources: National Weather Service Denver/Boulder, High Wind Safety and May 8, 2017 severe weather report; City and County of Denver, Roofing Guide and Checklist, updated 4/11/2024 (wind zones, nailing, flashing, crickets, ice barrier, snow load). EPA, UV radiation and sun exposure (surface UV depends on altitude, and EPA advises extra care at higher altitudes). The UL 2218 test description is from this site's earlier version of the article.
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