Tiling the hearth: prep part 2

Ok.  When we left off, we had demoed the old tile and started preparing for the new slate tile by pouring some concrete, selecting our tile, and cutting both the tile and edging.  We were a bit conservative pouring the concrete, so our pad was still a bit low.  After doing some more research online, I decided that using the Schluter Ditra underlayment would be a good way to bring up the height of the tile while also protecting against any cracks due to expansion and contraction of the wood floor.  Given the previous issue with the tile getting so jammed up against the wood that it created hideous cracks in the floor, taking the extra precaution against any problems seemed like a good idea.  I also figured we should use the underlayment when we do our entrance in the same tile, so why not buy it now and use it both places.  Note: using this for the hearth of a wood burning fireplace may be questionable due to heat issues, but it is fine for a gas insert. 

I installed the Ditra according to instructions (thinset mixed loose but still able to hold a notch, press Ditra fleece backing firmly into it, making sure to add enough thinset for complete coverage).

I attempted to install the tile right afterward.  Yes, attempted.  Did not succeed.  Here’s what happened.  I had everything all laid out and ready to go.  I’d read about how to do it.  I knew I still needed to come up about a quarter of an inch to make my tile flush with the wood floor, so I used extra thinset.  But I had mixed it too thin, and my Schluter edging kept sinking into it. 

I tried letting the thinset set up a little bit, but it was still not working.  I realized that I really needed two things to be different: mix the thinset to the proper consistency (duh) like peanut butter (it actually looks even oozier in the picture than it really was, but it was too thin for sure) and start at the right level so my edging could sit on it and not sink down.  My real problem was that I was trying to make a seamless transition between the hardwood and the tile so it would be level and flush, and I hadn’t created the ideal situation to achieve that.  So I decided to scratch the operation for the day and use what I’d learned to make it work on the next attempt.  Aside from the learning experience, I also got some use out of the thinset by combing it out to a level that would put me at the right height for installing the tile later.  This is my semi-defeated-but-also-semi-relieved-that-I-didn’t-completely-ruin-everything face:

And fortunately, dry (but not cured) thinset easily washes off of tile, edging, wood floors, arms, and tools. 

I put a piece of plywood over it with some random objects to keep dogs from stepping on it.  It did take longer to dry that way, but I don’t think that hurts anything. 

The next day, it was dryish.  I took that opportunity to level it a bit more using our screed from earlier with shims taped to the ends.  I pulled it from back to front, scraping off any high areas.  It worked quite well.

When the thinset was completely dry, I dry set my tile for probably the 7th of 12 times and checked the height.  It was still just a touch high in some areas, but the notches and the fact that it wasn’t cured yet made it easy to scrape down in high areas with the flat side of a trowel.  Here’s what it looked like after the scraping:

… and then I dry set my tile again.  Maybe I was paranoid cautious at this point, but I wanted to get it as close to perfect as I could so my next and hopefully final attempt at setting the tile would go smoothly.  So I taped some string across it and noted any high or low points (these variations were very small at this point).

When I felt that there were no points that were too high, the last thing I did was to lay a straight board across the tile. 

At various points, I measured how much space was between the board and the tile by slipping a shim underneath it and noting how much of the shim would fit.  I made a chart to remind myself where the tile should fit as tight as possible against the base and where I should put the thinset down a little thicker.

Was this all a bit much?  Maybe.  Do I think any of it was wasted time?  No.  I learned my lesson and I was going to set myself up for success in round two.  And I did; it went really smoothly.  I will tell you about it in the next - and final!!! - post in the hearth project series.