subfloor strength???

maronha243 · March 23, 2007, 03:44 PM

Myfloor joist are the following:

SILENTFLOOR TJI/PRO 120 TS, WHICH ARE 1 3/4'' WIDE BY 11 7/8'' TALL.
They span 17ft and are 16'' OC

I have 3/4'' osb on the floor. The floor joing the bathroom is 3/4'' hardwood. I don't want to be to much higher that the hardwood, but i guess i can alway put some sorta threshold there.

My shower kit is here, and I have done most of the replumbing to how I want it.

thanks mark

cproader · March 23, 2007, 04:37 PM

Ok Mark, we're gonna need alittle more info on what it is you are asking.

maronha243 · March 23, 2007, 05:02 PM

cproader said

Ok Mark, we're gonna need alittle more info on what it is you are asking.

Oh sorry i missed saying i would like to know about my floor deflection

Do i need more plywood over my 3/4'' osb?

I am wanting to use travertine tile, I will be using the kerdi shower kit.

Hope that helps a little.

mark

maronha243 · March 23, 2007, 06:00 PM

Let me add that my bathroom is 12'x12', but my joist run out to a bearing wall about 5'.( there is a hallway on the other side of the wall)

So is my longest span 12' or is it 17' like i said in my first post?

mark

stullis · March 24, 2007, 01:01 AM

Sounds like your span is 12'. Try the jump test. Does it feel solid. I have a kitchen floor that is a 15' span and I wouldn't put tile over my floor. Way too bouncy for my liking if I wanted ceramic.

A second layer of plywood is required for stone and is a good idea for ceramic.

maronha243 · March 24, 2007, 08:07 AM

stullis said

Sounds like your span is 12'. Try the jump test. Does it feel solid. I have a kitchen floor that is a 15' span and I wouldn't put tile over my floor. Way too bouncy for my liking if I wanted ceramic.

second layer of plywood is required for stone and is a good idea for ceramic.

I will say my floor feels really solid. I thought i was thinking about adding more plywood them using the detra membrane intead of the backerboard.

Bud Cline · March 24, 2007, 08:38 AM

Stone tile floors require double the strength (L/720) of that required for ceramic tile floors (L/360) and your actual deflection can be calculated by the manufacturers of the floor joist system. The conditions you state are minimal and they surely meet the lessor of the two deflections mentioned but don't techincally qualify for the stone application at this time in my view. The addition of 3/8" plywood and DITRA would most likely solve the problem.

maronha243 · March 24, 2007, 03:34 PM

What grade or kind of plywood do I need to use for the 2nd layer??

1) Any suggestions on a threshold or how to go about the floor differance . I have 3/4'' now so after another 3/8'' of plywood, 1/8'' for the detra and the tile is 1/2'' that will leave me about 1/4'' higher than my hardwood floor.

2) Is the detra generally only used for the floors only or is it good for using around the tube.

mark

stullis · March 24, 2007, 03:58 PM

I would use 3/8" arctic birch which is 7-ply stuff although you could probably get by with at least a BC or higher rated plywood.

A nice wood reducer finished to match your wood floor would look good.

Ditra could be used around the tub as well.

maronha243 · March 26, 2007, 05:34 PM

stullis said

I would use 3/8" arctic birch which is 7-ply stuff although you could probably get by with at least a BC or higher rated plywood.

A nice wood reducer finished to match your wood floor would look good.

Ditra could be used around the tub as well.

I looked at every stack of plywood in HD and only seen one stack of 3/8'' plywood which was primed on one side. Do most stores carry what i need?? I guess I need to get to lowes they always seem to have more selection arond here.

Nick Arrera · March 26, 2007, 06:23 PM

The box stores around here carry the low end of plywood . Did you try a lumber yard ?

maronha243 · March 27, 2007, 10:42 AM

No I did not but now that you said that I will just do that instead. I have a few around here.

Bud Cline · March 27, 2007, 06:37 PM

Exterior Grade Exposure 1 Plywood Underlayment should be available at all of the box stores.

maronha243 · March 27, 2007, 07:16 PM

Well I have plenty of stores/lumber yard around here so not to worry i will get my 3/8 plywood.

Any certain screw better than other for fastening the plywood?

When I lay the plywood it goes perpendicular to the joist just like the first layer of 3/4 correct?

Should I use glue also?

Jim Carlin · March 27, 2007, 08:15 PM

Bud is giving you extremely good advice.
The only thing I can add is, call the manufacturer with the markings on the joists. They will need it. Since they designed the truss joists, they are the only ones who can tell you with certainty if it is rated for tile or stone.
Jim