Ice dam risk in Waterville, ME
How often ice dams form in Waterville
40.9 dam days a winter
Severe risk. On an ordinary house in Waterville, conditions for an ice dam come on about 40.9 days in a normal winter, mostly in January and February.
Waterville averages 86 inches of snow a year and about 118 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 Waterville
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 19.9 | High |
| Typical, some insulation, not air-sealed | 40.9 | Severe |
| Older or poorly insulated, warm attic | 67.2 | Severe |
Sealing and insulating a typical attic takes out about 21.0 days a winter here. It drops the risk from severe to high. An older house with a warm attic should expect closer to 67.2 days.
Preventing ice dams on a Waterville 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 378 kWh a winter in Waterville, roughly $64 at 17 cents a kWh.
Which to spend on first: air sealing or heat cable.
Waterville winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 18.7 | 29.4 | 12.0 |
| February | 22.2 | 28.0 | 10.9 |
| March | 17.9 | 27.1 | 8.2 |
| April | 5.4 | 7.8 | 1.4 |
| May | 0.2 | 0.1 | 0.0 |
| October | 0.4 | 0.3 | 0.0 |
| November | 4.5 | 4.7 | 1.1 |
| December | 16.8 | 20.5 | 7.3 |
Waterville next to nearby towns
Waterville ranks 1 of 11 Maine cities here for ice-dam days, the worst in the state.
- Augusta, ME 15 mi, 30.3 days
- Lewiston, ME 40 mi, 33.3 days
- Auburn, ME 43 mi, 31.3 days
- Bangor, ME 47 mi, 29.5 days
- Westbrook, ME 67 mi, 22.4 days
Where these numbers come from
NOAA 1991–2020 climate normals from NEW Sharon, 17.8 miles from Waterville. 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.