Engineered truss joists and marble floor

[sbradbury]

I just started a bathroom remodel thinking I knew what I was doing with the tiling and then I came across this site, started reading and realized I really have no idea what I'm doing.

So, I have engineered truss joists, 19" on center, and as best I can measure 16' runs. The subfloor is 23/32 OSB. I had planned on laying 1/4" hardibacker ontop of the OSB with thinset, and then the 12x12 marble ontop of that.

Is this sufficient, or is there more I need to do? I know you guys are probably tired of answering the same newbie questions over and over, but I've been reading through here the last few days and don't see much talk about the engineered truss joists.

[jadnashua]

A couple of things...you need to go read the ID info on the joists and probably call the manufacturer to find out what their rated deflection is...unless the plans called for stone tile, they are probably not rated for stone tile. If you can find the manufacturer's marks on the joists, one of the people here (probably Bob) can look them up and let you know.

A stone install also calls for a second layer of ply (at least 3/8" and I think I'd want more with your spacing), and even if it was ceramic, might be a good idea since the spacing is larger than normal.

[sbradbury]

It's actually going to be 12x12 ceramic, I've had marble on my mind all day and typed the wrong thing in there.

Here's some pictures of what I'm working with... all the manufacturers stamps I can find and blurry and unreadable.

[bbcamp]

Those open-web trusses look to be at least 12" deep, so they should be fine for your 16 foot span and ceramic tile. It also appears that there is an interior partition wall supporting the trusses. If so, you can consider the span to be much shorter. Take some time to shim any of the trusses that are not fully supported by the wall. This will make your floor feel much stiffer and eliminate any potential for squeaks.

[sbradbury]

they're 18" tall. It also looks like every 3rd or 4th joist is doubled up, including the main one that runs underneath my bathroom, which is only about a 5'x8' area that's getting tiled. I'll make sure to shim the trusses up.

So I'm feeling pretty good about the floor for my tile now. Thanks for the comments guys.

[John Bridge]

Hi Strad, Give us a first name.

I would screw down the OSB to the trusses. I know nails were probably used, and there are probably voids.

[sbradbury]

Steve is my name.

Yes indeed nails were used. I will screw the OSB down before laying the backerboard. Thanks