Thinset over paint?

[Gofor]

Hello. My given name is Mark, Most people call me "Go". Either is fine with me. I am soon to attempt tiling for the first time. Project is two kitchen backsplashes (one over stove and one over sink). Have read through about 25 pages of posts yesterday after finding this great site. Based on that and previous research, I submit the following plan for your review. My ultimate question on this post is would it be a good idea to spread a skim coat of thinset over the painted drywall before I start tiling?
Game Plan:
Tile: Lowes 4 x 4 Venetian Stone (a color through porcelain tile almost 3/8" thick at the center. Appears to have either a clear glaze or is polished somewhat.
Layout - 45 degree diagonal
Spacing; 1/8"
Intended Adhesive: Laticrete 317 (White) with 333 admix
Intended Grout: Laticrete 1500 series Sanded Grout with 1776 admix
Trowel: 1/4 x 1/4 square notch
Substrate: Latex painted Drywall about 2 yrs old.
Wetsaw: HD $88 Workforce (I have tweaked it with a dremel tool, so table is now square and fence is parallel to blade). Cuts the tiles but don't know how many blades I will go through having about 200 or more cuts to make.
Tools on hand: Wetsaw, Trowel, 2 x 5 smooth margin trowel, Tile nippers, Sponges, buckets, mud mixer for the drill.
Materials: Have about 40 tile on hand, but have yet to purchase the remaing 225 tiles, thinset, grout, admixes, grout sealer, etc.
I plan to skimcoat the wall first to get a feel for the mixing and troweling. If I do, should I skim coat it with or without the admix? Am I correct in assuming the admix will reduce the amount of water needed in both the thinset and grout mix.
Sources for tools and materials are very limited locally (Lowes and a couple builder-supply warehouses that have little in the way of tiling supplies different from Lowes. (The nearest Home depot is a 40 mile drive each way). The only tile stores near are storefronts with samples.

I have pictures of the intended backsplash areas and one of my scale drawing layout. Will post if you want but don't want to clog up anyone on dial-up. I don't know your protocol on number of pics, etc.

Thank you for a very informative forum. I hope that I am not stepping onto a very steep slippery slope with this tile endeavor, but with a Mother-in-law, 5 sister-in laws, several nieces, etc here, I may be in trouble if this turns out good!! :lol2:

Any advice and comments will be appreciated.

Go

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[Davy]

Hi Go, welcome. :) I would sand the paint to rough it up real good. A skim coat won't hurt anything.

You might want some plastic wedges or tilespikes to shim the tile with. :)

[Gofor]

I have some Tavy spacers. With this heavy a tile, would the spikes save me some grief?

Go

[Rob Z]

Go

If using 333 in thinset or 1776 in grout, you will not add any water to the thinset. The only liquid it gets is from the latex admix. :)

[Gofor]

THANK YOU Rob. I would have made a mistake on that. At the store, the admix says"see the thinset instructions" On the thinset, the mix directions are unclear. I guess its the consistency that's the key, as the directions do have a +- sign by them. Makes sense now that I think about it.

Go

[rebeccatoner]

This is Andy rebecca's husband. I would not use thin set and sanding the paint is a mess. If it was me I would wipe the surfaces down with a non rinse T. S. P. cleaner. It will dull the finish of the paint so do not get it on the areas that you are not tiling. I would use a pre-mix mastic. You can find it at Lowes. If you read the back it will say for areas such as sheetrock and painted surfaces. Your tile saw will work but since it cuts under the tile first instead of from the top it likes to chip a lot. If you are going to down a lot of tiling in your house I would recommend a better tile saw. With the money you save on not hiring a tile setter its worth the pay and you will get professional results. I would recommend a saw that will last a long time and it small and compact. It will also cut 18" tile. Take the drive and go to home depot for it. It is a husky THD950L 7" tile/stone wet laser saw with stand. I purchased one for my small jobs. It cost about $300. If that is to much, your saw will work.

[Gofor]

Sink area: Tiled: Grout to be done in next day or two

[Gofor]

Stove area is tiled and grouted. After waiting 3 days to seal, should I seal and then put the silicone caulk on the bottom edge, or caulk first?
Thanks

Go

[Rob Z]

Go,

Looks great! :)

We usually caulk first and then seal everything.

[John Bridge]

Looks great, Go. :) You can seal any time after 24 hours. :)

[Gofor]

Thank you for the compliments and the info. Second wall is now grouted!! The info I gained from reading through the posts on this site were invaluable in me getting this far with no major disasters.
I did follow my original plan and used the materials I listed.
Some "Lessons learned"from a newbie:
1. Next time I will use TileSpikes instead of or augmented with the Tavys I have. The tavys fall out when you move an adjacent tile (at least with the thick rough beveled edge type tile I used).
2. If you use the Laticrete grout, buy more 1776 admix than the minimum. I ended up using more than the standard ratio (standard ratio gave me a crumbly mix. Probably used about 10% more than the standard). The shade we chose dried lighter than the color chart, but I had no problem with splotching using the admix. Next time I will start a shade darker than what I want and buy a small bit to do a sample.
3. If you skim coat a painted wall, realize than the thinset will start setting up immediately (the wall sucks the moisture out of it I guess). There won't be much time to try and level it out. I did notice that it improved the adhesion (had to pop a couple tiles off that moved. One in a small area without the skim coat and one main field tile. Both were removed about 1/2 hour after intial setting. The first one popped off with all the thinset on the tile, and none stuck to the wall. The second left almost all the skimcoat on the wall, and was much harder to pop off. After that, I made sure all areas were skim coated first.)
4. Professional tile setters have nothing to fear from me, and have my utmost admiration for the work they do!! :tup1:

Andy, thank you for your advice, and I did not discount it, but I wanted to get experience with the thinset. If I read this forum right, the thinset can be used for about every application, and the mastic for only a few. Also, my wife cooks some mean soup and chicken pastry, so the backsplash will get exposed to a lot of steaming goodies, therefore I went with the thinset + admix.

Thanks again

Go