Properly formulated and installed spray foam does not meaningfully shrink - it's dimensionally stable once cured. When you see shrinkage (foam pulling back from studs, gaps at edges), it's a symptom of an installation error, not a property of the product.
What actually causes shrinkage
- Off-ratio mixing - the two components must meter precisely; a bad ratio produces foam that cures wrong and can shrink or pull away.
- Wrong temperature - spraying on a too-cold substrate (a real Alberta risk) disrupts the reaction.
- Too thick per pass - closed-cell must be applied in controlled lifts; over-thick passes overheat and cure poorly.
Why it matters
Shrinkage opens the exact gaps the foam was supposed to seal - defeating the air-seal you paid for. It's preventable entirely by correct application.
The prevention
A CUFCA-certified installer working to CAN/ULC-S705, minding substrate temperature and lift thickness, produces foam that stays put. See signs of a bad install and certifications.
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