Ice dams are one of the most common winter roof problems around Lake Tahoe. The good news is that the cause is well understood, and most of the fix happens in the attic, not on the roof.
Why ice dams form
Warm air from the house leaks into the attic and warms the roof deck. Snow on the upper roof melts, runs down to the cold overhang and refreezes. The ridge grows, and water ponds behind it and works up under shingles. Tahoe’s deep, long-lasting snowpack and frequent freeze-thaw cycles give that process plenty of time to work.
Step 1: Air seal the attic
The U.S. Department of Energy’s Building America Solution Center and University of Minnesota Extension both put air sealing first. Common leaks: recessed lights, plumbing and wiring holes, chimney and flue chases, duct runs, top plates and the attic hatch. An energy auditor or insulation contractor can find them with a blower-door test.
Step 2: Insulate
Once leaks are sealed, add insulation to bring the attic up to recommended levels. Insulation without air sealing is much less effective against ice dams.
Step 3: Ventilate
Clear soffit vents and use baffles so insulation doesn’t block airflow. ENERGY STAR and Minnesota guidance note that ventilation helps keep the roof deck cold, and caution against powered attic fans, which can pull conditioned air into the attic.
Step 4: Ice barrier at the eave
Ice barrier membrane under the roofing helps keep backed-up water out. South Lake Tahoe’s building criteria require it, and Truckee’s code requires it from the eave to 5 feet past the interior wall line and 30 inches along each side of valleys. If you’re re-roofing, make sure it’s included.
Step 5: Manage snow at the edge
- A roof rake from the ground can pull snow off the lower few feet of a single-story roof. Never climb onto a snowy roof.
- Snow retention on metal roofs prevents dangerous slides and protects gutters.
- Clean gutters in fall so meltwater has somewhere to go.
Step 6: Heat cable where you need it
Heat cable at chronic problem spots keeps a drainage path open. It’s a useful backup, but guidance from Minnesota Commerce and Extension describes it as a temporary mitigation that doesn’t address the cause.
If you already have an ice dam
Don’t chip at it with tools or throw rock salt on the roof. Professional steam removal cuts channels safely. See ice dam removal.
Cathedral ceilings and older cabins
Vaulted ceilings without ventilated cavities and older cabins with little insulation are the hardest cases. Solutions may involve exterior insulation or venting during a re-roof. Get advice from a roofer or energy professional.
Request a free estimate to talk with a trusted local gutter pro.
Tahoe Gutters connects Lake Tahoe homeowners with an independent local gutter and roof-edge contractor. Work is performed by that contractor, not by this website. Cost figures on this site are general estimates from published national cost guides, not quotes.
Frequently asked questions
Will more attic insulation alone stop ice dams?
Not by itself. Air sealing comes first; insulation and ventilation follow.
Are ice dams a sign of a bad roof?
Usually they’re a sign of heat loss into the roof, not a bad roof covering. Ice barrier underlayment limits the damage.
Should I add more roof vents?
Not necessarily. Clear existing soffit vents and seal leaks first. Adding vents or powered fans can backfire.