I just had (and paid for) 2" of spray foam on my crawl space walls. I checked the thickness today and it is rarely 2" thick, usually just under 1.5", and sometimes just 1" thick.

Is this normal? Or should I be requesting a 25-ish% refund?

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    Not sure what you mean by "or are measurements like with wood," unless you're referring to finished lumber like a 2x4 being 1.5" x 3.5" (or a 2x6 being 1.5" x 5.5"). Of course, lumber is that way because it's saw cut to, say, 2" x 4", then planed smooth, taking 1/4" off each side. But with the foam, if you were promised 2" for the insulation R value, I personally would want it fixed so it's at least 2", or I'd want a refund, I suppose. On the other hand, if the promise was the sealant properties of the foam I think you're probably okay. That space is completely sealed against drafts. – Craig Jan 22 '15 at 17:08

No this is not normal. Spray foam (or XPS/EPS foam) provides a specific R value per inch in absolute terms. It is not at all related to how framing lumber is measured.

Rather then ask for a refund, I would ask the contractor to add more foam to meet the agreed upon thickness. Otherwise, you are trading efficiency and long-term savings for a short-term refund. Additionally, it would be difficult to calculate how much of a refund is appropriate. Easier to just fix the problem.

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