Ice dam risk in Sanford, ME
Ice dams in Sanford, ME: how often
29.0 dam days a winter
High risk. On an ordinary house in Sanford, conditions for an ice dam come on about 29.0 days in a normal winter, mostly in January and February.
Sanford averages 70 inches of snow a year and about 98 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 Sanford
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 17.2 | High |
| Typical, some insulation, not air-sealed | 29.0 | High |
| Older or poorly insulated, warm attic | 43.7 | Severe |
Sealing and insulating a typical attic takes out about 11.8 days a winter here. It does not move the risk band, but it shortens every dam. An older house with a warm attic should expect closer to 43.7 days.
What to do about ice dams in Sanford
- 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 212 kWh a winter in Sanford, roughly $36 at 17 cents a kWh.
Which to spend on first: air sealing or heat cable.
Sanford winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 18.5 | 28.5 | 9.8 |
| February | 20.1 | 25.8 | 8.7 |
| March | 11.6 | 22.2 | 5.4 |
| April | 2.4 | 4.9 | 0.6 |
| November | 1.5 | 1.3 | 0.2 |
| December | 16.0 | 15.3 | 4.3 |
Sanford next to nearby towns
Sanford ranks 6 of 11 Maine cities here for ice-dam days, behind Waterville at 40.9 days.
- Somersworth, NH 13 mi, 18.6 days
- Rochester, NH 14 mi, 18.6 days
- Dover, NH 18 mi, 18.6 days
- Biddeford, ME 18 mi, 22.6 days
- Saco, ME 18 mi, 22.4 days
Where these numbers come from
NOAA 1991–2020 climate normals from Cape Neddick, 15.1 miles from Sanford. 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.