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Unread 05-10-2019, 09:34 AM   #5
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Join Date: Dec 2015
Location: Berkeley, CA
Posts: 1,097
FWIW, there's a simple formula for determining deflection when you have sistered two different types of joists. Namely, if joist type 1 alone would have deflection L/A, and joist type 2 alone would have deflection L/B, then together they have deflection L/(A+B).

So if your original joist and their sisters have slightly different dimensions, or are different species/quality, you can run the deflectolator twice and add the denominators.

Cheers, Wayne
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