Ice Dam Sunday

[trevier]

correct venting and correct insulation will prevent that. Also a correctly done roof will also help.

[nightfighter]

Originally Posted by trevier

correct venting and correct insulation will prevent that. Also a correctly done roof will also help.

I agree with what you are saying, but some weather conditions can still wreak havoc. My house has an eight year old roof, and is properly vented. I could use more insulation. That said, the north, northwest sides of many houses locally have ice issues. I had even used a snow rake to remove snow from the bottom 3 feet. Still had a leak and still saw ice below the snow where I had raked the day before. To say "prevent" implies some sort of guaranty in my eyes.

[Liv2Fish]

The attic has to stay the same temp as the outside air. It will if you over insulate. Roll R19 across the existing R30 and put an insulation tent over the scuttle hole stairs. Careful of pot lights. Make sure they're IC rated. THey should be if they're in the a ceiling below an unheated space, but you never know who put them in.

Venting is as important but can be rendered useless but some type of venting. I always install soffit vent where possible instead of vented drip edge as the vented drip edge gets iced over and blocked. If it can't vent, the heat from the day combined with lost heat from the house will allow the layer of snow against the roof to melt and run down to the edge, where it hits the ice and freezes.

Temps just below freezing during the day are when we have the issues. As NF says, it's almost always the N or NW side that has the issues since there very little direct sun on that side this time of year.

[trevier]

I built my house in 2001-02, a 3 bedroom 2.5 bath cape. It has a full shed dormer in the back with 2 a dormers on the main in the front, never had any problems with ice dams and have never gotten up there and shoveled snow at all. Course it has 2x12 rafters on the front roof and 2x8 on the rear dormer with 5/8 plywood on the whole thing.