Chicago is hard on roofs. Few climates put a flat roof through so much in one year: heavy snow, ice, dozens of freeze-thaw swings, summer heat, severe thunderstorms and strong winds off Lake Michigan. For commercial buildings with low-slope roofs, each season brings its own kind of damage.
Here’s what Chicago weather does to a commercial roof, and what building owners can do to stay ahead of it.
1. Freeze-thaw cycles
In late fall, winter and early spring, Chicago temperatures often swing above and below freezing within the same day. Water that gets into a small crack or open seam freezes, expands, and pushes the gap wider. When it thaws, more water gets in. Over a single winter, a tiny opening can turn into a real leak.
What to watch for: open seams, cracked flashing, splits around pipes and vents, and blisters in the membrane.
2. Snow load and ice dams
A flat roof doesn’t shed snow the way a sloped roof does. Heavy, wet snow, and especially snow that melts and refreezes into ice, adds serious weight to the roof structure. Ice can also block drains and scuppers, so meltwater has nowhere to go and backs up under flashing.
What to watch for: drains buried in ice, sagging areas, and water stains near walls and roof edges after a thaw.
3. Ponding water
When snow melts or after a summer storm, water should drain off a commercial roof within about 48 hours. If it doesn’t, ponding water speeds up wear on the membrane, adds weight, and finds every weak seam. Clogged drains, sagging decks and poor slope are the usual causes.
What to watch for: dirt rings or algae marks where water sits, and puddles that remain two days after rain.
4. Wind off Lake Michigan
Strong gusts create uplift along roof edges and corners. Loose edge metal, copings and poorly attached membranes can peel back, and once wind gets under the membrane, damage spreads quickly. Buildings near the lakefront and in open industrial areas take the most wind.
What to watch for: lifted or bent edge metal, flapping membrane, and loose rooftop items.
5. Summer heat and UV
Dark roofs can get very hot in July and August. Heat and UV light dry out older membranes, cause shrinkage that pulls on flashing, and break down sealants. The big swing from summer heat to winter cold makes materials expand and contract all year long.
What to watch for: cracking, chalky or brittle surfaces, and flashing pulling away from walls.
6. Hail and severe storms
Spring and summer thunderstorms can bring hail that bruises or punctures membranes, dents metal roofs and damages rooftop units. Damage is not always visible from the ground, so a roof inspection after a hailstorm is worth it, especially if you plan to file an insurance claim.
How to protect your commercial roof from Chicago weather
- Inspect twice a year: in fall before winter and in spring after it.
- Keep drains clear: remove leaves in fall and check for ice in winter.
- Fix small problems fast: reseal seams and repair flashing before freeze-thaw makes them worse.
- Inspect after big storms: hail, high wind or heavy snow.
- Choose the right roof system: when it’s time to replace, pick a membrane suited to Chicago’s climate and your building.
- Consider a roof coating: on a roof that is still in fair condition, a coating can add a layer of protection and reflect summer heat.
A scheduled commercial roof maintenance program takes care of most of this for you.
Commercial roof repair in Chicago, any season
Mr. Roof & Remodeling Company has worked on roofs across Chicagoland and southeastern Wisconsin since 2011. We repair, maintain and replace TPO, EPDM, PVC, modified bitumen, metal and coated roofs on retail, office, industrial and multi-family buildings. If you have an active leak, our crews offer 24/7 emergency leak repair.
Call (877) 408-5405 or request a free quote to schedule an inspection. See all our commercial roofing services.