Ice dam risk in Flint, MI
How often ice dams form in Flint
19.5 dam days a winter
High risk. On an ordinary house in Flint, conditions for an ice dam come on about 19.5 days in a normal winter, mostly in January and February.
Flint averages 40 inches of snow a year and about 58 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 Flint
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 8.9 | Moderate |
| Typical, some insulation, not air-sealed | 19.5 | High |
| Older or poorly insulated, warm attic | 32.9 | High |
Sealing and insulating a typical attic takes out about 10.7 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 32.9 days.
What to do about ice dams in Flint
- 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.
Flint winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 13.1 | 19.9 | 7.6 |
| February | 10.4 | 15.7 | 5.8 |
| March | 4.3 | 8.8 | 2.2 |
| April | 1.2 | 0.9 | 0.1 |
| October | 0.1 | 0.0 | 0.0 |
| November | 1.7 | 1.6 | 0.3 |
| December | 9.6 | 11.0 | 3.5 |
Flint next to nearby towns
Flint ranks 38 of 90 Michigan cities here for ice-dam days, behind Sault Ste. Marie at 48.8 days.
- Burton, MI 4 mi, 21.4 days
- Fenton, MI 16 mi, 21.4 days
- Owosso, MI 25 mi, 22.5 days
- Saginaw, MI 30 mi, 21.6 days
- Pontiac, MI 33 mi, 19.6 days
Where these numbers come from
NOAA 1991–2020 climate normals from Flint 7W, 4.0 miles from Flint. 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.