Ice dam risk in Martinsville, IN

Ice dams in Martinsville, IN: how often

5.1 dam days a winter

Moderate risk. On an ordinary house in Martinsville, conditions for an ice dam come on about 5.1 days in a normal winter, mostly in January and February.

Martinsville averages 17 inches of snow a year and about 19 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 Martinsville

Attic	Dam days	Risk
Air-sealed and well insulated	3.0	Low
Typical, some insulation, not air-sealed	5.1	Moderate
Older or poorly insulated, warm attic	7.7	Moderate

Sealing and insulating a typical attic takes out about 2.1 days a winter here. It drops the risk from moderate to low.

What to do about ice dams in Martinsville

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.

Which to spend on first: air sealing or heat cable.

Martinsville winter, month by month

Month	Snow (in)	Days on ground	Dam days
January	6.3	7.6	2.4
February	3.8	4.9	1.3
March	2.1	1.4	0.2
April	0.1	0.1	0.0
October	0.1	0.0	0.0
November	0.4	0.3	0.0
December	3.9	4.3	1.1

Martinsville next to nearby towns

Martinsville ranks 76 of 88 Indiana cities here for ice-dam days, behind Plymouth at 15.9 days.

Mooresville, IN 13 mi, 7.0 days
Bargersville, IN 15 mi, 6.0 days
Bloomington, IN 18 mi, 5.1 days
Plainfield, IN 19 mi, 7.0 days
Franklin, IN 21 mi, 6.0 days

Where these numbers come from

NOAA 1991–2020 climate normals from Martinsville 2 SW, 1.3 miles from Martinsville. 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.