cement prep/how paranoid?

[browen]

Hey all,
I've done quite a bit of tiling around the house and now it's time for the living room. The nasty old carpet was pulled out two years ago and it wasn't long before the cement dust really started "collecting". Thinking I'd replace everything with carpet again, I applied a sealer to the bare concrete (JASCO seal & gloss). One year later I now have found a deal on some 18" travertine that will go in instead of future nasty carpet :^). For all the other tile installations I have done, including the travertine in the bathroom, I have used the latex modified thinset (versabond) and I plan on using this same product on this job. The floor is reasonably flat and the only cracks are very thin, flush, and haven't moved at all since exposed two years ago (slab is 20 years old).
Anyhoo, do I need to worry about removing the sealer? If so, what do I use? In the bathroom I used a belt sander to get rid of old vinyl, but this is about 300 sq-ft (ugh). Should I just plop down some of the thin set and see if it sticks? I'll probably use the same stuff as a leveler where needed. I'd hate to use stripper or other chemical means due to the fumes.

Thanks people!
-Bruce

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[John Bridge]

Hi Bruce, :)

Yep, remove the sealer. I'm going to move you to where our floor restore people can get at you. :)

[kemguru]

Hi Bruce :)

Jasco is a bear to remove. Methylene Chloride is the cheapest, quickest chemical that will take it. Makes your lips turn purple, though. :D

Since you don’t want the fumes, and it’s a concrete slab that will be tiled over, go at it mechanically. You can rent a scarifier from some rental stores. Call up a concrete supply store if you’re striking out at rental shops, they should know something. I prefer a scarifier, but other grinding/scratching/sanding equipment works great as well.

This will remove the seal and give you a wonderful surface profile. :)

[browen]

Blue lips never stopped me before javascript:smilie(':D')

So if it's a choice between the paint remover or mechanical means I guess I'll go mechanical. Rental is out due to my location so I'll probably go with a belt sander. I borrowed one for my bathroom and it worked excellent. Besides, I can't turn down a perfectly valid excuse to purchase a new power tool can I?

Thanks guys!

[John Bridge]

Bruce,

Three hundred feet of concrete floor with a belt sander? I'd rather take a whoopin'. :)

[flatfloor]

I'm thinking with the dust he mentioned and a belt sander taking it down, that isn't concrete, maybe gypcrete. Whats under the "concrete"?:shades:

[browen]

Excuses to buy new tools come far and few, I'll use any excuse I can! Besides, my sister in law has a belt sander and she keeps challenging me to races.

It's Gen-U-Whine concrete but it seems to cut with out too much effort when using a good belt. I also have a small area with some remains of old thinset that I'd rather cut down than chip out.

If I do go the chemical stripper route, how much cleanup will be required? The stripper usually can be washed out with water but do I need to go further? How about a followup with some acid based etcher?

-Bruce

[kemguru]

Bruce,

I recommend doing a light solvent wash after using these paste strippers. They contain wax and other thickeners that can interfere with thinset bonding. Paint thinner or lacquer thinner. A good acid wash is great after all this is said and done. You need to rinse well and neutralize after the acid. Modified thinset hates a low pH surface.

Use a wet-vac after each step, to ensure maximum removal. Extraction is key. ;)

[stullis]

That methylene chloride is NASTY stuff. HD doesn't even carry it anymore if that tells you something.

[browen]

It is nasty!

I can still find it, in fact the last can I got about a year ago was from HD. The key is reading the lable and confirming the contents.

I might give the stripper a go and try to find another way to clean up the stripper residue besides petro solvents. The house is heated with a wood stove and it's kinda cold outside to be leaving things open while the house airs out!
I was thinking I could sop up the mess with my wast collection of sawdust and just rinse the he!! out of it.

Another question, In the past whenever I tiled an area with a crack in the slab I was lucky enough to be able to place a grout line over the crack (and use caulking in place of the grout). The room I'm planning for has a long hairline crack that runs diagonal to my layout. I agree with someones sig line here that the only way to rest easy is knowing the job was done right. The crack will not "move" in my opinion, but it may expand/contract ever so slightly. Aside from covering the entire area with Ditra, can I just straddle this crack with a strip of Ditra wide enough to effectively allow the tile groutline to hide any movement? Basically I mean just use enough of the Ditra to allow several full rows of the tile to be isolated from the slab.

BTW, I really commend you guys for the effort you put into answering questions here! I know these type of boards get a lot of repeat questions yet based on some of your membership dates you have been answering stuff for years
Thanks!

-Bruce