replacing all above joists in bathroom reno... - DIY Chatroom

Bob the blunder · 12-02-2008, 11:51 PM

Howdy: I have demolished everything in my upstairs bathroom, all the way down to the studs and joists. My plan is to replace all floor materials and finish with ceramic tile or stone. What materials do I need to put down (including thicknesses) prior to laying the tile or stone. The joists are 2X8 on 16" centers and in very good condition. The floor dimensions are approx 8 1/2' by 10'. The floor will support a corner shower base/glass enclosure, a whirlpool tub + sink & toilet. Thanks in advance for the help.
Bob

JazMan · 12-03-2008, 01:00 AM

Hi Bob,

OK, you have 2x8 joists @ 16" o.c., what is the unsupported span? I recommend that you start by sistering those joists since the floor is open. But you should anyway because of the added weight the tub and in case you decide to install natural stone tiles. You also need to add additional joists or blocking to support ends of plywood that were cut, and so do not have t&g.

Your base subfloor should be 3/4" subfloor grade exposure 1. If you go with stone tiles and the joists are stiff enough, you will add a second sheet of plywood, I recommend at least 3/8", prefer 1/2" or thicker. You then install either a tile backer board or a membrane like Ditra. Then the easy part, the tiles. You may not need the second sheet of plywood if you stick with ceramic or porcelain tiles, but it would give you a better floor. The more plywood the better.

Measure and post back with the unsupported span and see if you can read the species and grade stamped on some of the joists.

Jaz

Clutchcargo · 12-03-2008, 10:40 AM

I'll be doing the same thing to my bath. You may be able to get away with a single 2x8 depending on the span. From what I've researched, you need to get an L/480 for tile or a L/720 for stone.
Use the span calculator here:
http://www.awc.org/calculators/span/...rcalcstyle.asp
I use Spruce-Pine-Fir #2 for the calcs.