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I am wanting to stiffen existing plywood subfloor in anticipation of a tile or stone (on mortar bed) finish floor.
is there any reason to favor adding more floor joists, vs. sistering existing joists ?
Applying glue to top of new joists before install would be a mess, would ring shank nails thru subfloor be good enough to prevent squeaking ?
Existing joists are 2×6, about 10-12 ft long (there is a beam in center of the 20 ft wide room).
There is plenty of crawl space under the first floor room, and relatively few obstructions.
Thx in advance for any advice.
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Adding more joists would lessen the span of your floor sheathing, but working on 8 or even 12" centers under an existing floor can be difficult. You will probably need a palm nailer. Sistering will be easier and will result in slightly stiffer joists, but won't improve the sheathing spans. I wouldn't worry about squeeking under a mortar bed, simpy screw (or nail) the existing sheathing to the new joists.
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tom h- you don't say what centers your joists are on, but if they're 2X6 DF-L @16", 10-12' span, you're beyond L/360 deflection. Sistering with 2X6 will do little to stiffen the floor. And, as Mike says, working in crawl space to install new joists will not be fun. Screwing your existing subfloor to the existing joists will help, adding add'l structural underlayment using adequate screws and/or construction adhesive could help also. If you really want to stiffen the floor, string line the existing 2X6's, jack at midspan to remove the deflection caused by the existing load, sister 2X8's to the 2X6's and remove jack. 2X8's, DF-L @ 16" are good for better than 12' at L/360.
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I am wanting to stiffen existing plywood subfloor in anticipation of a tile or stone (on mortar bed) finish floor.
is there any reason to favor adding more floor joists, vs. sistering existing joists ?
Applying glue to top of new joists before install would be a mess, would ring shank nails thru subfloor be good enough to prevent squeaking ?
Existing joists are 2x6, about 10-12 ft long (there is a beam in center of the 20 ft wide room).
There is plenty of crawl space under the first floor room, and relatively few obstructions.
Thx in advance for any advice.