Heavy Wet Snow: When to Worry About Your Roof in Michigan
Not all snow is the same load. Dry January powder and wet March slush can differ in weight several times over, and a roof cannot tell the difference by looking at the depth on the ground. This note covers what makes snow heavy, the signs an overloaded roof gives off, and when clearing it helps versus adds risk.
Homeowners hear a snow total in inches and file it next to the last storm with a similar number. That habit works for driveway shoveling and fails at roof safety, because inches measure depth, not weight, and weight is what a roof deck and its framing actually carry.
01 /Fluffy powder and saturated snow are not the same load
Snow is mostly trapped air. How much air, and how much liquid water is mixed in, separates a light powder from a dense, wet snowfall, and the weight difference per inch can be large. The National Weather Service Detroit/Pontiac office records is the range we defer to rather than quote one figure, since it shifts with temperature and wind. In practice, a foot of dry powder and a foot of heavy, wet late-winter snow can load the same roof span very differently, even at the same twelve inches on the ground.
Wet snow earns its weight two ways: it starts denser, since warmer air lets more liquid cling to each flake instead of forming loose crystals, and it keeps gaining weight after it lands, because a pack near the melting point absorbs rain or meltwater like a sponge. Dry powder mostly holds its weight the moment it falls. Wet snow can get heavier for days afterward, with no new snowfall at all.
02 /What the code number is actually for
Michigan's residential building code assigns Macomb County a ground snow load figure engineers use to size roof framing. The Michigan Residential Code's ground snow load for Macomb County, 25 pounds per square foot under Table R301.2(5), is that design number. It is worth knowing what it is not: not a warning threshold, and not the most snow a roof can survive. It is a structural design minimum with a built-in margin, and a properly built, maintained roof carries it without concern.
That margin gets tested by the roof as it has aged or been altered, not the roof as designed. A since-added sunroom, rot or fastener wear already present, or a drifted valley all start from a smaller margin than the code figure assumes. Our note on Metro Detroit's snowiest winters covers how a record season stacks that stress across a whole winter.
03 /Signs a roof is asking for help
A roof under real strain rarely fails silently; it tends to show in framing and finish work before the shingles themselves. Signs worth acting on:
- New sagging along the ridge or a roof plane. Visibly bowed where it looked straight before the storm is the clearest structural signal there is.
- Doors and windows that suddenly bind. Framing deflecting under load can rack the walls below just enough that doors and windows stick or stop latching.
- New cracks near the roofline. Fresh cracking where an interior wall meets the ceiling, especially spreading right after a heavy snow, is worth photographing.
- Creaking or popping under load. Occasional settling is normal. New, repeated creaking that tracks with snow accumulating is not something to wait out.
Any one of these is reason to call rather than guess. More than one together is reason to call today.
If you see warning signs, do not climb onto a snow or ice covered roof to look closer or relieve the load yourself. Snow hides the pitch, ice hides under the snow, and a fall is a far likelier outcome than a fixed problem. Load relief, if genuinely needed, is done from the ground with a roof rake, or by a professional with proper fall protection.
04 /When clearing snow helps, and when it just adds risk
For most homes in most winters, clearing roof snow is unnecessary; a code-built roof in good repair carries an ordinary snowpack, heavy and wet included. A roof rake earns its keep at the eaves, where snow and the ice dam it can start are more of a water-intrusion risk than a structural one, and a rake from the ground pulls that edge snow off safely.
What is never worth it is getting on the roof to shovel, whether the concern is weight or ice. If the warning signs above are present, or a roof carries known age or repair issues, the right move is a professional look. We inspect roofs across Macomb County for free, at no cost or obligation, and photograph what we find either way.
05 /What we recommend before and after a heavy snow
Before a wet system is forecast, clear gutters so meltwater has somewhere to go, and note any doors, windows, or cracks that already exist. After the storm, if anything on this list shows up, call rather than wait it out. Most snow-season findings are repairs, not replacements, and repairs run $350 to $3,200 (larger or complex repairs can run higher); the 60 second cost calculator uses those same figures.
If a heavy snow already found its way in as a leak, start at our storm damage service page; our line answers 24/7 for emergency tarping. Where insurance is part of the picture, the storm damage and insurance claims guide walks the process, and we can meet your adjuster on site, though no contractor promises what a carrier will approve. Our notes on ice storm glaze and the icicle watch cover other ways Michigan winters test a roof.
- Michigan Residential Code, 2015 edition, adopted with Michigan amendments by the LARA Bureau of Construction Codes, in effect since February 8, 2016. michigan.gov/lara: code books
- National Weather Service, Detroit/Pontiac forecast office: southeast Michigan forecasts, warnings, and event records. weather.gov/dtx