laundry room tiling on slab - help please

[cyberstever]

I am preparing to start a tile job in our laundry room.

I will be using American Olean Chloe Pinwheel Mosaic Gloss Black Tile & Stone- a 12 x 12 mosaic of 1x1 and 1x2 tiles on a mesh.
see fastfloors.com/lp_18470,0,129467/American-Olean-Tile-Stone/_/Chloe-Pinwheel-Mosaic-Gloss-Black/product.htm

The slab:
At ground level
Has some expansion joints that don't go all the way through
No movement (except in earthquake :-p ).
Mostly clean
About 70 (yes, 70) years old
Has an area or two that need to be filled prior to tiling.
If I leave a plastic bag or anything directly on the slab for an extended period of time, it will get some moisture under it. But there is never any standing water, nor does it feel wet to the touch otherwise.

I will need to transition to wall to wall carpet at the doorway.

I saw someone suggest in another thread to test if the thinset will bite by putting some water on the slab and making sure it gets absorbed. I'll give that a try.

Questions:
1) what to fill the joints with? What to fill the divot with (not a big hole, shown in closeup and almost visible in shot of room at far end right of toilet) ? I have a home depot near me, so custom building products (flexbond, versabond, multiset, etc) are easily available. is FixAll an ok choice?

2) any issues with the moisture i mentioned?

3) suggestions on what to do at the doorway threshold? The rug has a metal edge nailed into the concrete. Do i run tile to it or get a marble threshold and or remove the metal stop?

4) I assume i should fill the holes, etc and let it dry before I start tiling. Or is it ok to do both at the same time?

5) What should i use to bond the tile to the slab (flexbond, versabond, multiset, etc)?

6) I'm not overly concerned about layout since the the left and right sides are mostly covered by washing machines or cabinets. The far end will have the edge covered by baseboard.

7) anything else I should know? I've tiled a countertop, and a fireplace front. So, it's not my first time but I'm not anywhere near an expert...

I attached some images of the room, the area to be patched, the transition.

Thanks for the help!

[cyberstever]

I tried the water test and the water is not quickly absorbed. So, add to my list of questions - best way to scarify or prepare the concrete for tiling. It's about 8' x 12' .

Would really appreciate it if someone could take a look at the original post and give me some advice.

Thanks

[bbcamp]

1) Fill the divot with either brick mortar or a combination of thinset (as a painted on bonding agent) and deck mud. Don't fill the joints.

2) How long was a "extended period of time" and how much moisture did you collect? The test is for 48 hours, and you should see nothing. A calcium chloride test can be performed to quantify the moisture. However, I believe that if you carpet isn't suffering from moisture issues, your tile won't either.

3) Schluter makes a strip that covers the end of the tile and carpet. that may work. A marble threshold will do, too. It's more a design thing than a technical one.

4) Depends on how deep and what you use to fill. You will find it easier to do floor prep as a separate step than tiling.

5) Once you get the slab prepped to accept thinset, any modified thinset will do.

6) I'm not overly concerned, either. Thanks for asking.

You asked about the water absorption: Your slab was probably sealed a long time ago, since water will go away, albiet slowly. Rent a floor scarifier or grinder and remove just the top most bit of concrete, and any high spots you have. You could also use a diamond cup wheel on an angle grinder, too.

You asked about filling the control joints in. You have to install your tile so there is a grout line over each of those lines. Those lines are caulked, not grouted. This allows the slab to crack at those lines if it wants to. If you feel like gambling with your money and labor, fill the lines with brick mortar and tile over them. I wouldn't do it, because I don't gamble willingly.

Let me ask this: have you considered acid staining this slab? Those control joints and some of the patched divots will give your floor a aged stone look that can be very dramatic.

[cyberstever]

1) sounds good. Still considering filling the joints - they've been there for 70 years and there are no cracks in them yet. They only extend about 1/4" into the concrete, so it's not as if they go all the way through. If the tile joints line up nicely with them, I guess i'll just go with it and use caulk. If not, I may pre-fill with mortar and hope all is well. I don't gamble much, but I am just thinking it will be ok since there hasn't been any issues since the slab was put in. But if i really knew what I was doing I wouldn't be on this message board...

2) During the winter when the air is wet around here and the ground is saturated, anything left on the floor will get moist. During the dry summer months (Northern California, SF Bay Area) it's much less of a problem. I didn't do an official test, just telling you from experience.

3) the house is more traditional, so I'd love to get rid of the metal and put in some stone for a threshold.

4) makes sense. I'll have to see if i can rent something locally to do the scarifying.

5) I'll pick up some multiset or versabond since it's readily available

6) -

7) The acid staining is an interesting idea. I assume i would need to scarify first still? if I stain it and then decide i hate it (or if my wife decides that) do i scarify it again before moving on to the tiling? Most likely, to tie it into the rest of the house, we're just going to want to stain it.


Thanks for all the help!

[bbcamp]

Yes, you can scarify the surface, but try not to be aggressive. The concrete surface does not change because you stain it. Any tool marks will still be there. However, if random, they add character to the slab. You do not want to acid etch a slab that will be acid stained. That will remove the calcium based stuff that the acid stain needs to bond to.