Ice dam risk in Fond du Lac, WI
Will your roof get ice dams in Fond du Lac, WI?
27.6 dam days a winter
High risk. On an ordinary house in Fond du Lac, conditions for an ice dam come on about 27.6 days in a normal winter, mostly in January and February.
Fond du Lac averages 38 inches of snow a year and about 75 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 Fond du Lac
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 10.9 | Moderate |
| Typical, some insulation, not air-sealed | 27.6 | High |
| Older or poorly insulated, warm attic | 48.4 | Severe |
Sealing and insulating a typical attic takes out about 16.6 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 48.4 days.
Preventing ice dams on a Fond du Lac 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.
Which to spend on first: air sealing or heat cable.
Fond du Lac winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 10.8 | 23.2 | 9.9 |
| February | 9.9 | 21.9 | 8.6 |
| March | 5.7 | 10.4 | 2.8 |
| April | 2.4 | 1.4 | 0.1 |
| October | 0.4 | 0.1 | 0.0 |
| November | 1.7 | 3.0 | 0.6 |
| December | 7.1 | 15.2 | 5.5 |
Fond du Lac next to nearby towns
Fond du Lac ranks 35 of 98 Wisconsin cities here for ice-dam days, behind Wausau at 41.6 days.
- Waupun, WI 18 mi, 26.8 days
- Oshkosh, WI 18 mi, 27.2 days
- Neenah, WI 27 mi, 30.0 days
- West Bend, WI 28 mi, 24.6 days
- Beaver Dam, WI 28 mi, 26.8 days
Where these numbers come from
NOAA 1991–2020 climate normals from Fond Du Lac Wwtp, 1.7 miles from Fond du Lac. 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.