What type of flashing should be used at the base of stucco walls in Ottawa?

Base-of-wall flashing is one of the most critical — and most commonly botched — details in any Ottawa stucco installation. This is where water that gets behind the stucco (and it will, every spring) needs to exit the wall assembly. Get the flashing wrong and you're looking at rot, mould, and stucco delamination within a few years.

Proper Base Flashing for Ottawa Stucco Walls

The base-of-wall detail in Ottawa should include two components working together: a weep screed and a flashing membrane.

Weep screed: This is a perforated metal channel installed at the very bottom of the stucco wall, at least 150mm (6 inches) above grade per Ontario Building Code requirements, and at least 50mm (2 inches) above any hard surface like a patio or walkway. The screed serves as both a termination point for the stucco and a weep channel that lets trapped moisture drain out. Use galvanized steel or PVC weep screed — avoid plain steel that will rust and stain in Ottawa's wet conditions. A 10-foot length costs $8 to $15 depending on material.

Flashing membrane: Behind and beneath the weep screed, a self-adhering flashing membrane (like Grace Vycor Plus, Blueskin SA, or Resisto) should extend up the wall sheathing at least 200mm (8 inches) and out over the foundation ledge. This membrane catches any water that drains down behind the stucco and directs it outward through the weep screed openings. Self-adhering membranes run $1.50 to $3.00 per linear foot and are essential in Ottawa's climate.

Why this matters so much in Ottawa:

• Spring snowmelt against foundation walls can push moisture upward through capillary action. The base flashing creates a capillary break that stops ground moisture from wicking into the stucco- Ice damming at the base of walls (snow piled against the house all winter) means the bottom 12 inches of any Ottawa stucco wall sees the most moisture exposure. Without proper flashing, this zone fails first- The freeze-thaw cycling at grade level is more severe than higher up the wall because of splash-back from rain and snowmelt

Common mistakes Ottawa homeowners should watch for:

• Stucco carried all the way to grade or below grade with no weep screed — this traps moisture with no exit path- Weep screed installed but caulked shut along the bottom edge — defeats the entire purpose- Flashing membrane omitted behind the screed — water drains down but has nowhere to go except into the sheathing- Landscaping or mulch piled above the weep screed — blocks drainage and holds moisture against the stucco

Budget: Proper base flashing and weep screed installation adds roughly $8 to $15 per linear foot to the stucco job. For a typical Ottawa home with 150 linear feet of wall base, that's $1,200 to $2,250. It's a small fraction of the total stucco cost and arguably the single most important detail for long-term performance.

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