Tile Over Control Joints in Basement Slab

[ToadJones]

I have been reading a lot on the ole' internet about crack isolation membranes for tiling over "cracks" in concrete slabs to isolate "in-plane" movement to keep cracks from propagating up through the tile.

Is it necessary to honor a Control Joint that was cut in the slab strictly to control cracking?

The cuts in my basement slab have not moved since they were cut 5 yrs ago. Since it is below grade, I have a hard time believing that they ever really will. The slab confined on all sides by CMU walls. The only movement I would anticipate would be from water pressure below and that would cause "out of plane" movement and that can't be helped with any membrane.

Thoughts?

 

[OHIOMatt]

At 5 years in a conditioned space, the slab should have shrunk as much as it is going to. You have a relative constant temperature so thermal movements should be very small. I can't really see where it will be a problem.

 

[hokie66]

Use a flexible floor tile adhesive. You only need a tile control joint where there is a location such as a reentrant corner or narrow section like a door where a stress riser can occur.

 

[ToadJones]

So, you guys think I'd be safe to simply use a flexible thinset (I have used Laticrete with the latex additive in the past) and tile right over the joints?

 

[cvg]

you might check out this reference

http://www.tcnatile.com/faqs/24-crack-isolation-membrane.html

 

[ToadJones]

same vague information as everywhere else!

As far as I see it, these control cuts have long fulfilled there purpose and since the slab is some 7 ft below grade, and at a nearly constant temp I cant see thermal being an issue.
The 'crete has been curing for 5+ yrs...can't be shrinking too much anymore.

As I said above, water could be an issue if somehow it cause the slab to lift, but at that point no "Crack isolation" is going to help anyway.

 

[OHIOMatt]

If it were my house, I would tile right over the joint with the flexible thin set. To be on the safe side, I would buy some extra tiles for the "just in case" scenario. Will not cost too much and is a little insurance if there is a problem.