Tile over cracks

[hill_fan]

I just poured the hearth for my fireplace yesterday. I am planning on using a vermont red slate (1/4" gauged) and was going to thinset it to the 2" of concrete I poued over my existing slab.

The question I have is that when the concrete dried it had several hairline cracks through out... I know now that I probably mixed it too wet... Can I still tile over this? Will the cracks telegraph through eventually?

I would appreciate any help.

Thanks

[bkrahmer]

Did you use any rebar or wire? If the cracks were perpendicular to rebar, I certainly wouldn't worry about them. If there isn't any rebar, then I don't know...

[hill_fan]

I used mortar and metal lath.....its actually two coats the first I skimmed at 1 inch thinking that would be enough. I later realized that I needed to go an inch higher so I poured another inch..with no lath.

Hope that makes sense..

[dhill]

I doubt hairline cracks are going to be a problem. The thin set will fill some of those. But if they get to be wide cracks then you have problems. How long has the concrete set? Has it had time to settle out and cure to it's strength point? Some cement expert should be able to tell you how long you can expect to wait to see if little cracks will turn into big cracks.

[hill_fan]

Thanks for the help....

Yes, the cracks are small...and Im sure non-structural.

I just was'nt sure if the thinset would keep them from transferring to the tile but thinking it through it seem that if they are from shrinkage...and the mortar is set... then it should be fine.