Hi everyone, New to this forum and new to tiling in general. I am looking at replacing the laminate flooring in our bathroom with a tile floor. I was hoping to use run of the mill ceramic tile (Home Depot stuff) about 12"x12" or 18"x18". I want to make sure that I minimize the risk of the floor flexing and cracking my tile and/or grout. I have 2"x8" joists, on 16" centers, with a span of 11', and 5/8" OSB. The house was built in the mid 80's. I was wondering if I could apply mortar, a layer of Ditra 5M, mortar and then tile. Would that be sufficient to have a solid tile floor and low risk of flexing and cracking?

The mortar I found in Home Depot said it could withstand movement of 1/8". It was called MegaLite Premium Mortar.

Thanks for any input in advance.

I think this is the mortar that I saw at Home Depot. Even though the bag looks a little different and the name is slightly different.

http://www.custombuildingproducts.com/Pr...diy&lang=en

When I was at Home Depot, I specifically jotted down "MegaLite Premium Mortar". Further down on the bag it mentioned the 1/8" movement thing.

If you're talking about Ditra XL, the 5/8" OSB does meet Schluter's minimums for the subfloor. However, 5/8" subfloors scare me even if brand new and installed to specs. Is it t&g? If it is you may be ok.

However, I not sure about your joist system yet. You didn't say what species and grade those 2x8 are. I checked several species using #2 at 50/20 and you failed. Check that info and report back.

MegaLite is a newer formula mortar and work well in many cases. But, you shouldn't use it over Ditra and the 1/8" spec does nothing for you. That refers to horizontal movement as in shrinkage & expansion, not vertical movement.

Jaz

the Ditra5M stuff is not the XL stuff, it is the regular 1/8" thick Ditra

I believe the OSB is t&g

I have a little bit of access to the underside of my floor in my laundry/mechanical room. I will look to see if there are any markings on the joists. I am afraid that there won't be and I will not know what species and grade they are.

I'll check tonight and report back

thanks

ok, so I double checked some stuff this evening

the OSB is 5/8" and t&g, however I could not see any marking on the joist and unfortunately I can not identify it by looking at it. I do know that the pressure treated green lumber I used to build my deck was marked with SPF, which the guy at the local lumber yard told me stood for spruce-pine-fir and was a common lumber type in our region (atleast according to him)

OK, the 5M you mentioned has nothing to do with which Ditra. The 5M is the size of the roll, 5 meters long.

If you can't tell me which species and grade your joists are, I can't tell you much more. Generally however modern houses meet L360 deflection at 40/10 live/dead loads, sometimes just barely. With tile L360 is the minimum standard, but I like to meet that at 50/20 live/dead load. You can refer to the span calculator above left to see what I mean.

You might check any other joists in your house, or a neighbor if built at the same time by the same builder. Your town's building department may also know the species and grade.

Jaz