Wet Basements and Radon in Kingston: What Limestone Bedrock Means for the Room Under Your House

Radon: test first

Radon enters a house through cracks in the slab, the gap around the sewer pipe, sump pits and the joints of a stone foundation, and it accumulates in the lowest level. You cannot see or smell it; the only way to know is to test. Health Canada recommends a long-term test of at least three months, ideally over the heating season, using a kit from a hardware store, the Lung Association or a certified professional. Its guideline for action is 200 becquerels per cubic metre; some homes in the Kingston area test many times that.

If the result is above the guideline, a mitigator certified by the Canadian National Radon Proficiency Program can install a sub-slab depressurization system, a sealed pipe and fan that draws gas from under the slab and vents it above the roof. Most systems bring levels down by a large fraction within days, and the fan is the only moving part.

Damp basements on limestone

A Kingston basement dug into rock has water finding its way along the rock surface to the walls, and a stone foundation from the 1800s is porous by nature. Groundwater arrives at the wall-floor joint and through the mortar after rain and in the melt; sewer backup arrives at the floor drain during a storm and smells like sewage; and the old sewers under Sydenham and the Inner Harbour surcharge in summer thunderstorms. Photograph where the water first appeared and when.

For a stone foundation, the honest fix is exterior excavation, a membrane and new drainage where the lot allows it, and where it does not, interior drainage to a sump, repointed mortar and a dehumidified, uncluttered basement. Combined with a radon system, the sump pit must be sealed with a gasketed lid, which a mitigator will do.

• Radon test result and date
• Foundation type: poured, block or limestone
• Where water appears and when
• Camera inspection of the lateral if drains are slow
• Sump pit sealed if a radon system is installed

What the drainage fixes do, and who owns which pipe

A backwater valve is a one-way flap on the sanitary lateral that closes when the sewer surcharges so sewage cannot flow back into the house; while it is closed nothing in the house drains. A sump pump with a pit collects groundwater from the foundation drain and pumps it outside, with a battery backup for the outages that come with the storms. Utilities Kingston owns the sanitary and storm sewers beyond your property line and the water supply; the lateral on your property is yours, and a camera inspection with a locate tells you which side a fault is on. Utilities Kingston has offered protective plumbing programs at times; check the current page.

Heritage, contractors and who to hire

Radon mitigation is not a licensed trade in Ontario; look for C-NRPP certification, which is what Health Canada recognizes, and ask for a post-mitigation test to prove the result. Waterproofing is unlicensed too; ask for liability insurance and a WSIB clearance, and for a stone foundation, for examples of similar work in the old city. Many Kingston houses are heritage-designated, which can limit exterior excavation and visible changes; ask the City’s heritage staff before planning exterior waterproofing. Plumbing work needs a licensed plumber and a City permit for layout changes.