As snow turns to rain, how to keep the water outside

A week after London was buried by two large snowstorms, today's weather forecast is calling for up to 10 millimetres of rain and a daily high of 4 C. 

With so much snow on the ground, it's a weather combination that should have homeowners paying attention to potential water infiltration problems in their home.

"If it rains as much as they're calling for now, we're expecting some basements to have water issues," said Ken Moss with Best Plumbing and Drainage Contractors.

Contractors who spoke to CBC News said snow packed against a house foundation can spell trouble when it melts.

"You want to get the snow away from the foundation as much as you can," said Randy Weir, a project manager for Winmar Property Restoration. His company repairs homes damaged by everything from fires to floods. 

Weir said it's particularly important to shovel snow away from openings such as windows, doors and drains. 

He admits its not an easy task with so much snow on the ground. As the temperature rises, so does the moisture content in the snow, making it heavier to shovel. However he said any volume of snow you can pull away from the foundation will help.

Both contractors also said it's important to check snow-covered downspouts to ensure they're not clogged with snow, ice or debris. 

"It's good to try to keep that open so when it does start melting, the water has a place to run away," said Weir.  

Another thing to watch: Make sure any outdoor vents connected to heating equipment inside the house — such as a furnace or gas-powered water heater — are clear of snow and ice buildup.

"If those get covered with snow, it can turn your furnace off," said Weir. "We've had a lot of calls already for that." 

On the roof, ice damning is another problem that can come after a heavy snowfall. Ice dams form when snow on the roof is melted by warm air escaping from inside the house. As the water flows toward the end of the roof and away from the escaping heat, it re-freezes. The process continues until a damn is formed. Ice dams can damage gutters and lift shingles, causing leaks. 

There are ways to deal with ice dams but Weir doesn't recommend home owners try to deal with it themselves.    

"I wouldn't recommend raking it off yourself," he said. "Just leave it in place and if you don't have an issue inside the house, just let it melt naturally." 

As for fears that heavy snow could collapse the roof, Weir said most houses are built to handle significant snow loads. 

Sump pumps could be another source of trouble in a heavy melt situation. These pumps remove water from basement catchment plumbing. They're an essential line of defence against water infiltration and if they go down, the basement could fill up.

"We do sump pump inspections so if people know there's a melt or a rain coming, they can ask us to check them," said Moss. 

Any sump pump discharge lines that run to the surface should also be checked to ensure they're not clogged, said Moss. 

Ben Bates, owner of Advance Plumbing systems, recommends homeowners test their sump pump if rain or a snow melt is in the forecast and if it's been dry for a while. 

"Make sure it's plugged in, lift the float and make sure it comes on, or just put a few buckets of water down to see if it comes on," said Bates. "

Bates also said it's a good idea to have the sump pump inspected regularly, because if a storm or snow melt starts flooding basements, a contractor appointment can be hard to come by. 

"It's better to call before everyone else starts calling," he said.