Flooring Tile - tile on uneven floor.

i have a porch that is about 12x20. apparently it used to be half that size. it looks like the previous owner has another 12x10 slab poured to make it the current 12x20 size. there is a "seam" where the two slabs meet. there is a variation in height of the two slabs. not much, but enough that i can tell it won't work well for tiles along the "seam". any ideas on what i can do to either get rid of the uneven seam, or just tile over it? i'd hate to have one row of tiles that are tilted to one side because of the height difference. and i'd hate to have to lay down a self leveling mix over that entire area.

any ideas?

thanks,
mitch.

You gave the two options!

You could grind some of the higher part off to make it less noticeable and give it more gradual slope at the seam.

You can feather up the height difference with a variety of products but you MUST respect the seam between the 2 slabs.

It appears that you have a "cold joint" between 2 different pours of concrete. They will always behave differently and move in 2different directions at 2 different times.

The Tile Council of America calls for an expansion joint directly above the seam.. The easiest way is to put a "grout" joint over the seam---- but don't grout it. Fill it with silicone caulking to allow the 2 different slabs to move at their own pleasure.

If you cover the seam with a tile it WILL crack-- count on it.

so you're saying to fill the crack with silicone, and then just tile as normal? or fill it, and then make sure that the crack falls on a grout line (in between the tiles)?

IF the cracks can be leveled and the slab stays inplane there are crack isolation membrane's that can bridge the crack, that will allow the tiles to be set over the crack.
The TCA STATES -There are sheet and liquid membranes recommended by mfg. for installation of tile by thin set method over concrete which has or will crack. Follow mfg. written directions.

Is this area outside? What are the weather conditions? What part of the country do you live in?

Yes you could try the membrane method of covering the joint or you could use the expansion joint method.. If the seam in the concrete is an open crack of 1/4" or more you can put "backer rod" in it. Place your tiles so a grout joint is directly over the joint and caulk the grout joint with silicone.

it's a covered porch. i'm in florida... i don't think it's 1/4 inch crack, just an un-level joint. i gotta peel back the carpet to be sure.

you can quite often by a coler match caulk -Urethane is recommended however silicone is also excepted. The tile handbook spells out details.

That joint must be honored!

Even a membrane over that area is sketchy.

As WJS_SR51 states, The tile WILL crack along that cold joint. No if's, and's, or but's about it.

Movement is a tiles worst ememy. Those two slabs are going to move differently.

A grout joint must fall along that cold joint.
If a custom pattern is desired, then the tiles must be cut along a straight line above this joint and the joint filled with Sanded caulking of a color to match the surronding grout.

I would float the low side to be level with the higher side. Use the high side to screed off of, out the full 10 ft. or at least 6 ft.

Check out a crack isolation membrane. if it dosnt work, then you have what is being recomented a joint where you dont want it. however if it stays in plane it will most likely work.