Canadian Underwriter

A drastic (but effective) way to keep water out of the basement  

June 2, 2021   by Greg Meckbach

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A foundation membrane could cost a homeowner client $15,000, and it is probably not something your clients should try installing themselves, but it is “often the most effective method” of waterproofing a basement, a author suggests.

A foundation membrane is a thick sheet of rubberized asphalt on waterproof polyethylene film that goes outside the foundation, Tom Scalisi wrote in How Much Does Basement Waterproofing Cost? Basement Sealing Budgeting Guide, recently published on Acton Media Inc.’s site. Bob Vila has hosted several do-it-yourself television shows such as This Old House.

A foundation membrane is rarely a do-it-yourself job, Scalisi warned.

Other ways your homeowner clients could reduce basement flood risk include adding interior paint coatings, cutting drains into the floor, and re-grading the exterior landscape, wrote Scalisi.

An inch of water in the basement can cause damage of up to $25,000 or higher, warns Insurance Jack, a division of Petley-Hare Limited, a brokerage with 12 Ontario offices.

Causes of basement flooding include improper sealing on the flooring and walls, hot water tank failure, sump pump failure, water supply line failure, sewer backup, or a clogged gutter system, Insurance Jack noted in How to Prevent Basement Flooding, an article published recently on its website.

Some homeowners do not understand how gutters keep the basement dry, Scalisi wrote for

“Without gutters, the massive amount of rain that a roof can collect in a rainstorm will drip down the shingles and land no more than a foot from the foundation walls — a perfect recipe for a wet basement,” wrote Scalisi.

“Ensuring that your gutters are pitched correctly and free from clogs and debris is essential, or else water will back up over the brim of the gutter and drop in front of the foundation.”

To stop water from penetrating basement walls, the homeowner can repair either the outside or inside of the foundation.

“If the foundation is in rough shape, no amount of waterproofing will work, and the structure can actually be unsafe,” Scalisi wrote. “In that case, you’ll need to have the walls repaired before you can move forward. The foundation repair cost will be extra, depending on how extensive the repairs are. But these repairs are crucial to ensure a waterproof foundation.”

Scalisi advises homeowners to ensure downspouts send water at least eight feet away from the foundation.

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