Ice dam risk in Lawrence, IN
How often ice dams form in Lawrence
8.1 dam days a winter
Moderate risk. On an ordinary house in Lawrence, conditions for an ice dam come on about 8.1 days in a normal winter, mostly in January and February.
Lawrence averages 27 inches of snow a year and about 30 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 Lawrence
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 4.6 | Low |
| Typical, some insulation, not air-sealed | 8.1 | Moderate |
| Older or poorly insulated, warm attic | 12.6 | Moderate |
Sealing and insulating a typical attic takes out about 3.5 days a winter here. It drops the risk from moderate to low. An older house with a warm attic should expect closer to 12.6 days.
What to do about ice dams in Lawrence
- 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.
Lawrence winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 8.4 | 11.4 | 3.6 |
| February | 7.2 | 9.2 | 2.5 |
| March | 3.6 | 2.4 | 0.4 |
| April | 0.2 | 0.1 | 0.0 |
| November | 0.6 | 0.4 | 0.1 |
| December | 6.7 | 6.6 | 1.6 |
Lawrence next to nearby towns
Lawrence ranks 50 of 88 Indiana cities here for ice-dam days, behind Plymouth at 15.9 days.
- McCordsville, IN 4 mi, 8.1 days
- Fishers, IN 7 mi, 8.1 days
- Indianapolis, IN 10 mi, 7.0 days
- Carmel, IN 11 mi, 8.1 days
- Beech Grove, IN 12 mi, 7.0 days
Where these numbers come from
NOAA 1991–2020 climate normals from Castleton 2 S, 3.4 miles from Lawrence. 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.