Ice dam risk in Wausau, WI
How often ice dams form in Wausau
41.6 dam days a winter
Severe risk. On an ordinary house in Wausau, conditions for an ice dam come on about 41.6 days in a normal winter, mostly in January and February.
Wausau averages 64 inches of snow a year and about 112 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 Wausau
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 16.1 | High |
| Typical, some insulation, not air-sealed | 41.6 | Severe |
| Older or poorly insulated, warm attic | 73.4 | Severe |
Sealing and insulating a typical attic takes out about 25.5 days a winter here. It drops the risk from severe to high. An older house with a warm attic should expect closer to 73.4 days.
Preventing ice dams on a Wausau roof
- 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.
- Heat cable is worth pricing here even on a sealed house, along the eave and in the gutters and downspouts it drains into.
Running 60 feet of 5 W/ft cable whenever snow lies below freezing would use about 458 kWh a winter in Wausau, roughly $78 at 17 cents a kWh.
Which to spend on first: air sealing or heat cable.
Wausau winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 14.8 | 29.8 | 13.3 |
| February | 12.7 | 28.0 | 11.3 |
| March | 8.3 | 20.6 | 5.5 |
| April | 6.5 | 3.6 | 0.5 |
| May | 0.2 | 0.0 | 0.0 |
| October | 0.9 | 0.2 | 0.0 |
| November | 6.5 | 5.7 | 1.4 |
| December | 14.4 | 23.9 | 9.6 |
Wausau next to nearby towns
Wausau ranks 1 of 98 Wisconsin cities here for ice-dam days, the worst in the state.
- Weston, WI 7 mi, 41.6 days
- Stevens Point, WI 31 mi, 37.8 days
- Marshfield, WI 33 mi, 37.5 days
- Plover, WI 35 mi, 37.8 days
- Wisconsin Rapids, WI 40 mi, 37.8 days
Where these numbers come from
NOAA 1991–2020 climate normals from Wausau, 2.6 miles from Wausau. 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.