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Unread 12-22-2019, 10:47 PM   #8
Dun Wright
Registered User
Join Date: Oct 2019
Posts: 18
Deflection test? Situation too funky to calculate on JP calculator

Working on a kitchen floor which had 12x12 natural stone tiles on top of 1/2" hardibacker which was over 3/4" x 6" diagonally ran plank subfloor which was on top of 1 1/2 x 5 1/4 floor joists from the 1950s. 3 tiles in the whole kitchen were cracked and that was directly over a hardibacker joint and in a weak spot in the floor (could feel the "squish" when bouncing lightly).

Tore it all out down to the 1 1/2" x 6" x 12' long floor joists. YIKES. Talk about undersized floor joists! The 2x6's run 12 feet (unsupported) and are 12" on center. I sistered 1 3/4 x 5 1/2 Microlam 2.0 LVLs to each joist and then added 2x6 blocking every 3 feet. I then covered with 3/4" (height restrictions to old floor) Advantech subfloor.

The floor is about 32234234 times more stiff than it was before based on my scientific fat man walking/bouncing tests. The wonderful John Bridge Calculator wont work in my situation. Is there a test I can do to see if natural or ceramic tile will indeed be ok? I have laser levels, a lot of fat friends, and many tape measures if that helps any....
Thanks in advance, love this place.
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