Should I install a sump pump in my new addition's foundation in Ottawa?

Often, yes, but the right answer depends on your soil, groundwater and how the addition connects to the existing house's drainage. Many Ottawa lots have clay soils, which drain slowly, and some areas see high groundwater during spring melt and heavy rain. A sump pit with a pump is a common way to deal with the water your new perimeter drainage collects around the addition's footings. Your designer or contractor will confirm what the foundation drainage needs to be for your lot.

The typical setup is a sump pit at a low point of the new foundation, connected to the perimeter drainage pipe around the footings, with a submersible pump that discharges the water away from the house. Pump size depends on how much water you expect; your contractor can recommend a unit based on your site and on how the existing house's sump, if there is one, has behaved. Another option is tying the addition's drainage into the existing system, but ask whether that system has the capacity.

Soil type matters. Clay and silt soils are frost-susceptible and can heave, while sands and gravels generally don't. If the addition sits on sensitive clay, including Leda clay, or on filled ground, the Ontario Building Code requires footing sizes to be engineered, and your engineer will consider drainage as part of that design.

Winter is a real concern for the discharge line. A line that runs above ground can freeze, and water dumped too close to the house can find its way back to the foundation. Ask your contractor how they will route and protect the discharge so it drains away from your home and your neighbour's property all year.

Power outages are the other risk. A backup pump, battery-powered or otherwise, keeps the pit from overflowing if the power goes out during a storm. Ask your contractor about backup options and how long they can run. The pump needs a proper electrical supply; electrical work needs an ESA notification and is done by an electrical contractor licensed by ESA.

Installing a pump during construction costs far less than dealing with a wet addition later, so ask for the drainage, pit, pump, backup and discharge to be itemized in each quote. If you're unsure about permit requirements, Building Code Services can help (buildingpermits@ottawa.ca). You can browse addition contractors in the Ottawa Construction Network directory at justynrookcontracting.com and compare quotes.

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