House Works: Your questions on a stubborn leaking roof, rooftop snow, fan condensation
Solving Mysterious Water Leak
Q: What’s causing a stubborn water leak around the entrance to our house? Water most often comes through our front entrance light box and/or through the popcorn ceiling at the entrance or in the den to the right or living room ceilings to the left. We’ve brought in roofing people, a structural engineer and even replaced the roof over an ice and water membrane. The leak still happens.
A: Sorry to hear about your trouble. Leaks like this can be a real worry and disruption. Do these leaks happen most often in the spring, as winter temperatures warm up? If the leaks never happen in summer, then it’s almost certain to be caused by melting wintertime frost inside your attic or an unheated storage area, not a water leak through the roof. This dynamic often fools even the experts because they’re not looking for frost to be the culprit.
If warm, indoor air is allowed to enter a cold area of your home such as an attic or crawlspace, it’ll condense then freeze as frost on surfaces. The longer the cold spell continues, the larger the buildup of hidden frost will become as warm air keeps condensing and freezing.
When the weather finally warms up, all that frost will melt over the course of a day or two, creating the illusion of a roof leak. Sometimes people have multiple leak events over the course of a winter as cold weather changes to warm and back again. If your leaks happen when it’s not raining and never in winter, then you’ve got a frost problem for sure. The solution involves sealing the area where indoor air leaks are happening. Most often this involves the use of spray foam.
Dealing With Rooftop Snow
Q: What can I do about lots of snow that slides off the main roof of our house onto a relatively small part of the verandah roof?
A: Does your verandah roof show signs of stress from the extra snow? It might be okay to leave things as they are. If you’re concerned, one approach approach would be to install hardware to keep the snow from sliding down the main roof. In the photos you sent your roof appears to be covered in asphalt shingles. Normally this doesn’t allow snow to slide, unless the roof is steep like yours. Hardware is made to keep snow from sliding off metal roofs, and that would be useful in your case. These are usually metal brackets that fasten to the roof and stick upwards, giving something for the snow to hang on to.
If you can keep the snow on the main roof, there’s no chance of overloading the verandah.
Bathroom Vent Condensation
Q: What’s causing the yellow stains on the bathroom exhaust fan vent at the eaves of my house? There are stains on the snow below, too.
A: This is probably due to condensation forming inside the duct during cold weather, then running down and out of the vent. This may have been happening other winters and you didn’t notice it, or it may be worse this year because of the long periods of cold weather we’ve been having. If the metal duct isn’t insulated as it runs through unheated areas such as an attic, condensation will definitely occur.
One way to check is by watching the outdoor vent while someone is showering with the fan on. If my hunch is right, you’ll see liquid water dripping down.
A little bit of condensation like this in the duct is no problem, but if the duct is accessible as it runs through cold areas you should add insulation to the outside or replace the duct with a version that has built-in insulation.
Steve Maxwell is wise to the sneaky ways of frost, condensation and Canadian winters. Sign up for Steve’s free Saturday morning newsletter at BaileyLineRoad.com