Days 5-6: Floor Prep

Tile Selection and Layout

We decided to tile the whole unit. We chose a "Roman Noce" style, and decided that we didn't want to do it in a boring, regular rectangular grid pattern, just to make things interesting, so we decided on a "hopscotch" (also called a "pinwheel" pattern). We looked into the cost of having a contractor install (and remove the old tile). It was going to be expensive: $5000 for the tile + materials (grout, thinset, etc), and something like $6500 for removal, floor prep, and install. Since we were doing everything else, we decided that I would do the strip, prep, and install, to save a bunch of money. As of today (Jan 19 2010) I have installed about half, so I'm going to describe the tips and tricks I've learned so far. Previously, I described how I removed the old tile and thinset and carpet. So now I'm left with a blank, but messy concrete floor.

Floor Prep

I read over and over again that floor prep is the most important part to a successful tile install, so I wanted to do it "right". I did a "water test" where I sprinkled some water on the floor in various spots, looking for a good rate of absorption. Apparently if the water beads on the surface instead of soaking in, then it's not going to bond well with the thinset. So I decided to attempt to "scarify" or rough up the floor. Plus it seemed that the floor that was under the old carpet was really smooth and maybe had some kind of sealant or other coating on it from the original pour.
Finally, there was a bunch of paint on the floor, especially near the walls where the baseboards were spraypainted, and the overspray hit the floor. The original painters also used the floor to paint closet doors, and other various things. I was pretty sure the thinset would not bond to this at all, so it needed to come off. Also, there were some spots where I missed the thinset with the jackhammer, so I figured some hard sandpaper would take that off.

Floor Buffer

Enter a big "floor buffer" which is the giant heavy rotating head that you see janitors using to wax or buff shiny floors. I attached some 20 grit sandpaper to it and went to town on the concrete. It was a dusty mess, and didn't seem to be doing much, but I kept at it, going over every square inch I could. Since the buffer rotates (I'd guess around 500 rpm or more), every time I'd bump against a wall the thing would shoot left or right. Eventually I got the hang of driving the thing, but in tight corners it was an interesting pinball bounce effect :)

Unfortunately, driving over the paint didn't magically bring it up in many spots, as the paint has had 14 years to sit. If you just press hard on the floor buffer to attempt to get it up, it will shoot fast one way or another, so the trick is to get it going fast one way, then press down on it on the side of the buffer that cancels out the speed in that direction. You can really press down hard to cancel out its lateral speed, but you have to time it so that when you press down on it, you're over the spot you really want to grind down. So I was able to get up "most" of the paints in the center of the room and in the doorways with this technique. For the paint nearest the walls, I found the best way was to use a small razor blade paint scraper, that did the trick (using several blades, and the concrete wears down the blades pretty fast). Also, watch out for any tack strip nails you may have missed. Hitting that with the floor buffer usually results in torn sandpaper.

After sanding twice, I vacuumed up the dust with my shopvac. The fine dust will clog your shopvac filter pretty fast, so I would open it up and beat on the filter to clear it as best I could. Had to do that 4 or 5 times across all 1800 sq ft. Make sure to turn your A/C off and open windows, etc etc. Tons of dust. You will look like a ghost as will everything inside.

I was unable to get into the really tight spots (like behind the toilet) but figured these areas would see virtually no foot traffic ever, so it's not super important that the tile be 100% solid there. Same as against a wall. No one walks within 6" of a wall unless it's in a hallway or something. I also am counting on the small holes left from tack strips will give a nice solid bonding spot for tiles near the walls.

I also made sure to go around the cabinets and walls where the tile used to be, to remove as much old tile as I could so I can butt the new tile up against the old. I removed the "kickboards" under the cabinets (they usually just pull straight off, as they were nailed with some cheap nails or staples in the first place). I tried not to move the tile directly underneath the feet of the cabinets, as that is what is supporting the front of the cabinets. I also took out the fridge and oven and removed the tile from there.

After 2 days of sanding and vacuuming, I had a sanded floor with most of the paint removed. On to making the floor level!