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Unread 10-24-2020, 07:22 PM   #19
risotttto
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Join Date: Oct 2020
Location: Queens NY
Posts: 17
Excellent structural info, jadnashua!

I finally got a peek into the subfloor using the remote camera, as I suspected it looks like the joists are engineered "Silent Floor" brand stamped on the side, with Laminated Veneer Lumber in the center, not OSB. They are 16" high, around 2" thick at the top and bottom, thankfully just a few holes for electrical cable. I'm taking the span should be around 20 feet for the entire width of the building.

So the Deflecto is still technically no good as it does not work with engineered lumber, but would the engineered joists be stiffer than the SYP or Doug Fir of a similar size? I get L/678 using the same dimensions and spacing on the Deflecto.

Also trying to reverse read these tables for a similar joist, and looks like the lightest-duty 16" joist at 22' span would give you greater than L/480 according to the table at 19.2 spacing...

I also just found that the "Silent Floor" was a system trademarked by Truss-Joint, who is now owned by Weyerhaeuser, so that table is for the current version of the product. Who knows if it was the same in 1991 when the building was built.

Still too sketchy for slate with 1.5" of subfloor and underlayment?
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Last edited by risotttto; 10-24-2020 at 07:52 PM. Reason: found joist manufacturer
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