Ice dam risk in Gloucester, MA
Ice dams in Gloucester, MA: how often
12.5 dam days a winter
Moderate risk. On an ordinary house in Gloucester, conditions for an ice dam come on about 12.5 days in a normal winter, mostly in February and January.
Gloucester averages 51 inches of snow a year and about 48 days with snow on the ground. Most of it comes and goes within a few days. 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 Gloucester
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 8.5 | Moderate |
| Typical, some insulation, not air-sealed | 12.5 | Moderate |
| Older or poorly insulated, warm attic | 17.5 | High |
Sealing and insulating a typical attic takes out about 4.0 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 17.5 days.
What to do about ice dams in Gloucester
- 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.
Which to spend on first: air sealing or heat cable.
Gloucester winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 16.0 | 14.3 | 4.4 |
| February | 16.4 | 14.9 | 4.3 |
| March | 7.6 | 10.3 | 2.1 |
| April | 1.4 | 1.3 | 0.1 |
| October | 0.3 | 0.1 | 0.0 |
| November | 0.9 | 0.9 | 0.1 |
| December | 8.8 | 6.6 | 1.6 |
Gloucester next to nearby towns
Gloucester ranks 41 of 58 Massachusetts cities here for ice-dam days, behind Pittsfield at 31.3 days.
- Beverly, MA 10 mi, 12.5 days
- Salem, MA 14 mi, 9.5 days
- Peabody, MA 16 mi, 9.8 days
- Newburyport, MA 16 mi, 20.7 days
- Lynn, MA 18 mi, 9.5 days
Where these numbers come from
NOAA 1991–2020 climate normals from Beverly, 8.2 miles from Gloucester. 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.