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Bcoleman6 02-21-2008 12:20 PM

Sister floor joists or build support wall?
I have two projects in the works. The first is building a bedroom in the basement below the kitchen and the second is to tile the kitchen floor. The joists are true 2 x 8, 16" OC with a 12' span. According to John Bridge's deflection calculator this is borderline for ceramic tile. Currently the sub floor is 1 x 8 boards which run at an angle.
So what to do? When I build the bedroom it will include a wall perpendicular to the joists, is it possible to build this wall to be load bearing? If so it would make the span 10' or should I just sister the joists? If i do either of the above can I just use 1/4" hardibacker on top of the current plank sub floor, or do I need to rip out the planks and put down 3/4" ply and 1/4" hardibacker or leave the planks and put 5/8" ply and hardibacker. Not doing the kitchen floor until next year but if I need to sister the joists, now is the time.

Sorry for the long post.


Rehabber 02-21-2008 12:37 PM

If you are going to build that wall anaway, that will be sufficient support to reduce the deflection

Bcoleman6 02-21-2008 12:41 PM

Thanks for the quick reply.

Will a 2 x 4 header be enough?

Rehabber 02-21-2008 01:06 PM

If you line up the studs below the joists, that should be fine

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