[philS]

Googled and searched threads here for "garage floor" but didn;t really find what i need, which is advice on flooring options. I'm willing to buy and install porcelain or ceramic tile, but I'd like it to last and be easy to clean. Tips and other options would be appreciated.

Specifics:

30x30 concrete shop/garage, poured concrete slab, plus 10x15 ft sloped entry apron. Located in tropics, moderately marine environment.

Slab got finished very rough (like max 1/4 " screed marks (don't ask) plus cement dribbles from the plastering) but is otherwise in excellent shape. Poured in 4 parts, 3 inside plus the entry apron. Very fine cracks between the pours but they haven;t widened (4 years). Some paint spills which I can chip off if necessary.

Structure used mainly as shop. Tractor is stored inside when I'm away but so far only a few scatttered oil dribbles. But a material that won't absorb oil if I do spill it would be wonderful.

As I said, the surface is rough and obviously I want to minimize the amount of chipping down I have to do.

Thanks. -- Phil

 

[ccarlisle]

The main issue with tiling on top of a concrete slab is not what it looks like on top, it's what's underneath the slab that will affect the tiling job as much as the job done on the surface. Find out what has been done before the slab was even poured and go from there...the surface dressing and the products sitting on the concrete are well-documented.

 

[philS]

"What's underneath" is easy to answer. Compacted dirt, then compacted gravel. No moisture barrier, if that's what you're getting at. Though a tropical site near the ocean, it is technically desert. Cactus everywhere, mezquite. Rain comes in spurts (19" in 3 hours last fall, which may be a local record), but in between the soil stays really dry. I poured the slab in the dry season so i doubt there was much moisture trapped underneath. No sign of it wicking up the through the floor as exflorescence.

 

[ccarlisle]

Well then great, you're perhaps in an area where the moisture breathing requirement of the slab is minimal, where bonding issues from underneath are less and therefore you can take shot at tiling it by addressing the waterproofing and cracking issues from on top.

Now for this you have two choices: mud bed or thinset. Doing a mud bed is fairly an 'art' not everyone can do a good job at it and the other is more friendly IMO. Now depending on how you've addressed existing or future cracking, both will require some sort of membrane between the tile and the concrete and the use of grout + thinset. Use a quality product in either case.

One method we have used calls for 'Ditra' (a membrane), applied with unmodified thinset onto a clean and dust-free floor, then tiles set on that again with unmodified thinset. Make sure the coverage of the thinset underneatht the tiles is 95% or better...

Otherwise it's epoxy...and that's stressful!:laughing:

 

[philS]

CCarlisle - Thanks for the reply. Today I went by our largest local construction supply house (non big box) and talked with their tile "guy". She and I finally settled on a ceramic tile made by Jarama. (This is Puerto Rico incidentally so most of the tile here is imported from Europe.) It seems like a good combo of some surface roughness but a very sealed/tight finish. She said definitely thin-set (polymer added), not cement, and that I could put the thin-set on as thick as needed to deal with the roughness in the slab. I asked her about membranes and as I suspected no one here uses them.

A little clarification on the slab. It's about 5" thick, 3500# mix, heavily reinforced with #4 rebar (like maybe 18" grid). The steel is tied into the stemwalls, which the slab rests on top of (ie slab doesn;t float). This is earthquake country so we build strong. I really don't expect it will crack unless we get the big one.

I've done three bathroom tile floors with thinset but always on top of backer board, not directly on a slab, so I know a little about it but I've still got questions:

Can I really put the thinset on as thick as I want? If so, should I still use a notched trowel before placing the tile? It's 13x13 tile so would 1/4x1/4 notch be ok?

Can I mix the thinset in my electric cement mixer? It's an Imer and has mixed many hundreds of loads of cement mortar and concrete but I've never tried it with thinset. Any tips? They're 50 lb bags.

Does this sound at all reasonable? What am I not considering? Any other thoughts from anyone on how I might avoid screwups would be very welcome. I won;t start on this until next week at the earliest.

Phil

 

[ccarlisle]

Phil:

That all sounds like a reasonably well-thought out plan; if you decide to go with no membrane, that's fine too, it's your house after all and I promise not to squeal on you...:wink:

In that case, modified thinset is great. The description of the slab would only add to the green light for thinset only. The membrane would be overkill because you're not dealing with the issues it addresses: moisture from below and uncoupling. V-notch trowel is fine, as is the mixer.

Have fun!