How clean is clean before putting down porcelain

[wesalexleft]

Okay, I know this is a vague question and I'm likely to get any number of answers, but just looking for advice. I've pulled the trigger and have 500 sq.ft. of 18", PEI IV, porcelain tile stacked and ready to put down. The concrete it's going over is a 40 y/o pad and the concrete is the texture of sidewalk (rough). It's reasonably clean with a few oil spots that I plan on spot cleaning with mineral spirits, etc, but they're not beading water now. I pressure washed the concrete in the fall, and will do so again before tiling. Is there anything else I'd need to do? I don't want a weekend tiling project to become a week long concrete scrubbing,but of course I don't want to have tiles popping loose either. I will be using the Kerabond/Keralastic. Also, after washing, how long before tiling? I see some advice saying to wait days, while other sites say to pre-wet concrete to avoid flash drying of the thin set.

thanks,

 

[duneslider]

If the water will absorb into all areas of the slab it is clean enough. You say it is a rough texture, this is a GOOD thing. It will give it more grab and make a better bond.

Don't use mineral spirits. I would use an acid etcher and/or hit it with a diamond blade grinder wheel to make sure clean concrete is exposed. If you use the acid make sure to wash good after.

As long as you don't have puddles it is dry enough. I wipe concrete with a damp sponge right before spreading thinset.

Burn the thinset into the tile and the concrete floor. Do this by spreading a thin layer of thinset with the flat side of the trowel. This forces thinset into all the nooks and crannies and GREATLY increases the bond. I would say you probably will need a 1/2"x1/2" trowel for tile that size. You want 100% coverage, what this means is that if you lift up a tile you don't want to see any trowel marks!!!!! Very important!!!!

Kerabond/Keralastic is a fantastic setup but might be overkill. If you will be seeing freezing temps it is probably good to go that combo, if it won't ever freeze then I wouldn't spend that much money.

I highly recommend honoring any control joints in your cement floor.

 

[Bradford]

According to your thread my suggestion is that...As long as you don't have puddles it is dry enough. I wipe concrete with a damp sponge right before spreading thin set.

 

[wesalexleft]

Thanks for the input so far. I hope to pressure wash Friday evening and start laying tile Saturday morning. The tile has a raised grid on the underside. I will skim coat the back of the tile to fill the voids (backbutter). I hadn't thought of skimming the slab to force in thinset, but will now do that as well before going with the notched coat. I'll spot clean any oil spots as I go. I will seat the tiles with twisting motion followed by rubber mallet to seat them and level them. Any other tips?

 

[myslow2002gt]

I think you have it all covered now.

As mentioned, burning in the thinset as well as backbuttering will yield a very impressive bond. Follow that procedure all the way through and you'll have a very durable floor for many years.

 

[machine_punk]

There is a new method recommended by the tile folks...use the notched trowel in a straight line (not swooping curves) and

This video is well worth a watch, before you tile. The video is a little on the dorky side, but has good information and demonstrations on how and why to apply thinset...

YouTube has a bunch of videos on laying tile...was quite helpful to me, before starting my tiling project.

I just tiled a bathroom floor...I'm not sure how you are going to have time to spot clean WHILE you are tiling. Once thinset is mixed, you've only got about 4 hours before it starts hardening significantly. I think I would have the floor COMPLETELY ready to go, before starting to lay tile.


OH...and lessons from the trenches...

- Get yourself a pair on knee pads...you will still be sore, but you won't have bruises.

- Get yourself a good tile cutter. At least get a manual tile cutter...the one with two, long bars (like a paper cutter). DO NOT try to score and cut tiles with the things which look like pliers. Those might work for small mosaics, but they stink for laying any sort of real tile.

- 'Shuffle' your tile...to make sure the tiles are all random die lots. Open all of your boxes of tile and mix them up with each other, so you don't have any significant color changes over the floor.

- I liked mixing the thinset in a 5-gallon bucket, with the rotating mixer you get for the drill. They sell semi-transparent buckets with the markings on them. Get one of the smaller graduated buckets for adding water accurately to your thinset.

- I got a smaller pointing trowel for moving thinset around. Put thinset in the hard to reach areas first, then pull it out to the open areas. Then push it into the floor with the flat edge of the trowel and go back over it in STRAIGHT LINES with the notched edge of the trowel.

Kev

 

[Dakota00]

The garage floor should be degreased and washed at least a day before any tiles are laid.

Once the kerabond/Keralastic is mixed you don't have a long working time before it starts setting up. Do not over mix, mix the thinset let it rest for 1-2min and give it a quick spin again. Read the instructions!! It's not like regular thinset where you have time to play with it.

 

[wesalexleft]

Thanks again and keep'em coming. Looks like I won't be tiling this weekend after all as the temps are getting revised downward with new highs around 55-60 but lows still in the 30's. Definately need to get knee pads. I've done about 600 sq.ft. inside, and now that you mention it, I remember really wanting a pair over the foam kneeling pad. Already have a mixer, good scoring cutter and a wet saw.(Can't beat the metal Harbor Freight model for $50.00). I'll be sure to degrease/wash again the day before tiling. I really don't have much oil..just a few spots from leaking rear main and a leaking rear seal repaired just recently. I haven'tworked with the Keralastic before, so I'll be sure to follow the directions on it. I've used another latex modifier indoors though and it went well. That tile is still stuck to the 70's mosiac ceramic tile beneath it. I'll check out the YouTube vids as well.

 

[duneslider]

I haven't noticed the K/K open time to be really short. Not as short as Rapid set anyway. If you are moving slower, just mix a half bucket at a time.

 

[machine_punk]

Yes...there are certainly ways to get around shorter set times...I really just meant that you cannot expect to be doing other things (stopping to clean a spot on the floor), while you are actually putting down thinset and tiling. That is all you are going to have time to do (absolutely all floor prep should be completed before tiling).

Kev

 

[Shea]

There are a lot of great tips here. The one I didn't see that I would highly recommend for a large floor is to use a 6' level to insure that you are getting a nice flat and even surface (though not necessarily level). It really comes in handy and works much better than just sighting it in.