"franz fripplfrappl" wrote in message
...
I have a small cabin 20x24. The floor joist system is comprised of
2x8x10 joists resting on outside wall and a center beam. The ends of
each joist are notched with the equivalent of a 2x4 tongue resting on the
walls and center beam.

Joists are spaced 24" o.c. for the most part. Subfloor is 3/4" plywood.

I would like to reduce/eliminate floor deflection sufficiently that I
will be able to install ceramic tiles with an appropriate backer board.

1) 10' isn't examply a "super long" span. You might actually run some
tests whereby you actually measure the deflection. You might consider
added another 1/2" to 3/4" of plywood on the top. This would give you
"bullet proof" support in the 24" between the joists.

2) This isn't "standard" but you might consider adding a 2x4/10 to the
bottom of your existing joists. This isn't "sistering" but actually
converting the bottom of the joist into a "half I-beam." The connection
between your added 2x4x10 and the existing joist has to be good. You might
consider "glue and screws." The 2x4x10 has to be good stuff without
significant knots. Just increasing the debth of the joists will reduce
deflection by more than 1/3 (the strength increase with the equal of the
height). With the extra wood, there might be even less deflection.

I have thought of installing additional 2x8x10 joists with all joists 12"
o.c. Unfortunately the availability of good 2x8's just is not the case.

I'm looking for options:

1. Instead of 2x8's positioned between existing joists, could I use
2x6's?

Compared to the 2x8's the 2x6's are useless.

2. Could I sister 2x6's with existing 2x8's?

Huh?


3. Would sistering 2x4's with 2x8's provide sufficient stiffening?

Huh?

Thanks.



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Franz Fripplfrappl


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