All of the Schluter Ditra is down and cured. The instructions said I could lay tile immediately following the adherence of thinset below the Ditra. I am not that quick or prepared. These pictures show the measuring method I used to see how to start the tile laying portion of the project. The room fit the tile very nicely with only minor cutting. The far side of the room only had an inch or two taken off. It just didn't seem necessary to split the difference with so little removed. Especially since the far side of the room will be mostly hidden behind the breakfast nook table. There are quite a few tiles that had to be cut to fit around things on the perimeter. Heating vents, desk supports, stair handrail posts, and bay window angles all had to be marked off and cut out.