Ice dam risk in Detroit, MI
Ice dams in Detroit, MI: how often
15.1 dam days a winter
High risk. On an ordinary house in Detroit, conditions for an ice dam come on about 15.1 days in a normal winter, mostly in January and February.
Detroit averages 31 inches of snow a year and about 50 days with snow on the ground. Most of it comes and goes within a few days. The conditions that make a dam need all three at once: snow, cold at the eave and heat above it.
What your attic does to that number in Detroit
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 8.3 | Moderate |
| Typical, some insulation, not air-sealed | 15.1 | High |
| Older or poorly insulated, warm attic | 23.6 | High |
Sealing and insulating a typical attic takes out about 6.8 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 23.6 days.
What to do about ice dams in Detroit
- Air-seal the attic floor: the gaps around the hatch, light fixtures, plumbing stacks and the top plates of interior walls. This is the fix that removes the cause, and it usually costs less than a season of contractor ice removal.
- Rake the bottom three or four feet of roof after any storm that leaves more than about six inches, from the ground with a roof rake.
- At the next reroof, ask for ice-and-water membrane under the shingles from the eave to at least 24 inches inside the wall line. It does not stop a dam; it stops the leak when one forms.
Which to spend on first: air sealing or heat cable.
Detroit winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 11.7 | 17.9 | 6.3 |
| February | 7.3 | 16.4 | 5.2 |
| March | 5.7 | 6.6 | 1.4 |
| April | 0.6 | 0.2 | 0.0 |
| November | 0.9 | 0.9 | 0.1 |
| December | 4.6 | 7.6 | 2.1 |
Detroit next to nearby towns
Detroit ranks 67 of 90 Michigan cities here for ice-dam days, behind Sault Ste. Marie at 48.8 days.
- Hamtramck, MI 3 mi, 15.5 days
- Hazel Park, MI 5 mi, 15.5 days
- Ferndale, MI 5 mi, 15.9 days
- Oak Park, MI 7 mi, 18.1 days
- Dearborn, MI 7 mi, 14.2 days
Where these numbers come from
NOAA 1991–2020 climate normals from Dearborn, 8.2 miles from Detroit. A dam day is a day with snow on the roof and freezing at the eave while heat or sun melts the snow above it. This describes a normal winter, not this one.
- Snow-on-the-ground counts come from a second, nearby station, because the closest one does not record them.