Ice dam risk in Platteville, WI
Ice dams in Platteville, WI: how often
28.8 dam days a winter
High risk. On an ordinary house in Platteville, conditions for an ice dam come on about 28.8 days in a normal winter, mostly in January and February.
Platteville averages 43 inches of snow a year and about 80 days with snow on the ground. Snow that lies that long is what turns a little attic heat into a ridge of ice at the eave. 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 Platteville
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 12.1 | Moderate |
| Typical, some insulation, not air-sealed | 28.8 | High |
| Older or poorly insulated, warm attic | 49.7 | Severe |
Sealing and insulating a typical attic takes out about 16.7 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 49.7 days.
What to do about ice dams in Platteville
- 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.
Platteville winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 11.0 | 24.5 | 10.5 |
| February | 9.8 | 21.3 | 7.8 |
| March | 6.1 | 9.5 | 2.3 |
| April | 1.6 | 0.9 | 0.1 |
| May | 0.1 | 0.0 | 0.0 |
| October | 0.4 | 0.2 | 0.0 |
| November | 1.9 | 2.9 | 0.6 |
| December | 11.9 | 20.2 | 7.5 |
Platteville next to nearby towns
Platteville ranks 33 of 98 Wisconsin cities here for ice-dam days, behind Wausau at 41.6 days.
- Dubuque, IA 20 mi, 23.9 days
- Monroe, WI 43 mi, 24.4 days
- Verona, WI 50 mi, 22.2 days
- Freeport, IL 52 mi, 19.2 days
- Middleton, WI 55 mi, 22.2 days
Where these numbers come from
NOAA 1991–2020 climate normals from Platteville, 1.5 miles from Platteville. 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.