Frozen Roof Stacks

December 13th 2010
Frozen Roof Stacks

A common question that comes up every winter season from homeowners across western Canada is the issue of frozen roof stacks. The vent stack takes all the moisture and exhaust from within your homes water supply, like sinks, Showers, toilets, floor drains and all sanitary drains, and exhausts them through your roof cavity.

The warm vapor moving up the stack must be exhausted, and as the moisture hits the sub zero outside temperature it condenses, freezes, and continues to build up until eventually, the roof stack will plug shut.

Some suggest that insulating the vent stack within the attic cavity will fix the problem, but the attic is not where the problem lies. Others suggest installing one of the various styles of sewer vents that resist plugging and are available from hardware stores and building centers, but these vents are costly, and you can fix the issue without buying any alternate materials.


The higher the roof stack rises above your roof line, the more condensation to take place and build up within the pipe, so the easiest solution to prevent this from happening continually, is to cut the vent stack shorter, giving the moisture a quicker route to dissipate into the open air. Be sure to cut the roof stack no shorter than 6 inches from the roof line and re-cap it with the appropriate vent cover.

It's Just that Easy!