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Stiffening Existing Floor Joists

Stiffening Existing Floor Joists

Stiffening Existing Floor Joists

I was recently asked to stiffen an existing floor system. They are planning on adding expensive tile, and are worried about cracking. The floor framing is 2x10 joists @ 16" o.c. with 1/2" and 3/4" sheathing spanning 15'3" and are way under for deflection. The product specs recommend l/720 to eliminate any cracking, which is difficult given the span and crowded nature of the basement (increasing depth would be difficult with wiring and duct work). Sistering on one or both sides does not meet the deflection criteria. Any recommendations on stiffening the floor, or avoiding tile cracking?

RE: Stiffening Existing Floor Joists

Add top and bottom steel plates? Or flitch plates? A little steel goes a long way.

RE: Stiffening Existing Floor Joists

Light gauge steel "C" joists.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

RE: Stiffening Existing Floor Joists

What about sistering with engineered lumber?

RE: Stiffening Existing Floor Joists

Adding a flush or drop beam to shorten the spans.

Mike McCann, PE, SE (WA)

RE: Stiffening Existing Floor Joists

most cost effective would probably add a LVL beam mid span (msquareds solution), and if that doesn't give the desired result laminate another D.Fir 2x10 to every joist in addition to the beam

RE: Stiffening Existing Floor Joists

Expanding: The tables I set up for 2x joists show 15'3 is max span of 2x10@16" with L/360 - cut the floor joists down the middle and add in a beam (make sure it isn't a continous span, you just want half length trib widths

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