Remember that Kerdi is 8 mils thick, about 1/125th of an inch thick.

Multiple layers are usually not a problem unless you have too much thinset between your layers of Kerdi.

Often times I'll comb out a regular amount of thinset and use finger pressure to set the tile as I need it to keep the tile in plane. Meaning after setting the tile I'll have the regular amount of thinset between the tile and the single layer of Kerdi, and maybe a little less thinset between the tile and the multiple layers of Kerdi.

However, if your Kerdi thickness is excessive, then yes, you can feather the differential across a couple of tiles, but that will throw your wall out of plane.

Mongo

Thanks Mongo
I think my Lowe's "Floor Adhesive" thinset had some coarser sand in it so the layers are a bit thicker than I would have liked. Not too bad though. This only seems to be affecting the window sill and sides so no worries about the wall plane.
Thanks for the help,

ggoose

terriks, yup, it's portland-based and from Laticrete. Good follow-up though.

yup, it's portland-based and from Laticrete. Good follow-up though.

That's a relief. The word "adhesive" always sends up alarm bells for me.

Me too. :-)