Ceramic Tile on basement concrete (with some cracks)

The safe way is to put a membrane down. If the crack is truly stable you could use flex mortar but if that crack moves it will usually transfer through the tile

Can you recommend a specific example of membrane? Something available at a big box store?

Decouple the tile with Ditra.

Something like this. I am not sure if the BORG has it but a tile wholesaler will

Hmm... I reviewed the installation video. It suggests placing this decoupl ing membrane over the -entire- basement floor, not just the immediate area of the crack(s). Are you suggesting to use it over only the cracks and fea ther up to it as needed? Is that common practice? Sorry for so many quest ions, but I'm not really sure what to do ...and I really don't want to end up with popping tiles.

Ditra from Schleuter?

Use it as designed to decouple the tile from the ENTIRE subfloor.

They generally do the whole floor.

i would install a interior french drain around the entire basement perimete r so you will KNOW water will never ever be a problem, have the existing fl oor ground to remove all traces of paint, install the decoupling membrame, then tile. drain to daylight is excellent.

If water has not been a problem and the exterior drain is working well, adding an interior "french drain" is just an expensive answer to a question that has not been asked - an exopensive solution? to a problem that doesn't exist, and a good way to screw up an otherwise good floor. If the water is collected outside the foundation perimeter it should never get into the basement. The only exception would be if the house is built on a spring - and if that was the case the water problem would already be VERY evident. I don't get the fascination some people have with destroying the integrety of a concrete basement floor to install what usually ends up being a totally useless extra problem.

I agree. My sister had a wet basement and was talked into a drain system with a pump. The pump pretty much ran all the time, just recirculating the same water I imagine. They finally plumbed it into a sewer (illegally) and fixed the problem.

Bulk water is really not a problem, and so I've no interest in another peri meter drain. I'm just frustrated that these products seem to suggest I have to cover all 800sf of basement with an isolation membrane. That's close to $1k investm ent that I wasn't expecting, but I may have to resign myself to. My house i s 60+years old, so I don't expect new cracks to form where none existed. I' m wondering if there is any type of isolation membrane that can be feathere d up to and span over just the cracks (or maybe 18" on either side of crack s). Thoughts?

An "isolation membrane" that does not isolate the WHOLE floor cannot do it's job, If you want to play, you have to pay - to do the job RIGHT a decoupler of some sort is pretty well a requirement - and the isolation membrane is about as simple as it comes. After all the cracked tile I've seen in buildings where the tile was installed directly to the concrete, there is NO WAY I'd accept that kind of tile installation. Same with tile over wood sub-floors. It's not cheap - untill you compare it to the cost of redoing a tile floor every couple of years because of cracks.

You are really worrying about the slabs shifting relative to each other. The membrane isolates this movement but it needs to do more than just span the gap.

You might look into something like this although I have no experience with it.

It's my basement and I want to do this ONCE, so I totally get what you're saying.

Thank you all for the very informative repsonses.

its far easier to be proactive by installing a interior french drain ideally draining to daylight so no pumps are needed.

than to install a tile floor only to find water issues later

my moms home had a water problem. i spent 8 grand and was the laborer on the job to save money......

installed a exterior french drain, all new downspout drains , all new re sloped yard, new sidewalks. it was a thing of beauty. nice dry basement. installed a vinyl tile floor..

inside looked great too, till the basement had water troubles again.

destroyed the nice tile floor.

had interior french drain and floor redone.

sold he home..

i have the experience of been there done that and got the diploma:(

once that tile floor is in, its forever.....

will your basement be dry forever?

Unless the basement isn't dry forever

Please see above ;-)

Definitely better than nothing, but not the same as something like Ditra.