Flooring Tile - Tiling bathroom floor w/ heating

I'm planning on tiling our bathroom and would like to make the floor heated as well. I've read about some sort of alternative to cement board below the tile (kind of a honeycomb or eggshell-like plastic material that's about 1/8"-1/4" thick) ... can that be used with a heated floor or will i have to use cement board under the tile?

Thermal expansion at rates introduced by heat mats/cable systems can create problems if that movement is not given accomodation. Ditra, which you described, does a very good job in that situation.

I don't think you are going to run into problems with a conventional install using cbu and then heat cables in a bathroom providing all the norms for expansion and installation are followed.

More important starting point would be the specifics of the structure first. Post back with the unsupported span of the joists, their spacing and their size. (Measuring the distance below of supporting walls or beams for span, stud finder if the ceiling below is finished, and drilling a small hole in a closet and inserting a piece of wire to measure joist size), what you have for a subfloor including how thick, and every layer on it. We'll guide you from there.

Thermal expansion at rates introduced by heat mats/cable systems can create problems if that movement is not given accomodation. Ditra, which you described, does a very good job in that situation.

yeah, that's it! couldn't think of the name ... we're trying to add as little height as possible since the tile floor meets a hardwood floor in the hallway


More important starting point would be the specifics of the structure first. Post back with the unsupported span of the joists, their spacing and their size. (Measuring the distance below of supporting walls or beams for span, stud finder if the ceiling below is finished, and drilling a small hole in a closet and inserting a piece of wire to measure joist size), what you have for a subfloor including how thick, and every layer on it. We'll guide you from there.

floor thickness: ~ 1 1/2" (sub floor + plywood, each approx 1/2 the total thickness, so 3/4")

joist spacing: 14 1/2"

size: 1 1/2" x 9"

if it helps, here is the layout of the bathroom, incl measurements: http://lloydnet.org/Gallery/House/Projects/BathroomRemodel/Bathroom-Top-Down.png.html

i'm not exactly sure what you mean by "unsupported span of the joists" ... there is a bathroom directly below this bathroom that is a little smaller ... and there's a closet below the proposed cabinet / hamper area (the bathroom isn't quite like that drawing, since that's the first phase of the remodel!), so there are quite a few walls under the bathroom area (the joists run from left-to-right in that drawing) and i'm guessing the longest span b/n walls that are perpendicular to the joists would be about 7ft 7 3/4in (the same as the distance from the door to the right-hand side of the drawing) ... since we rent the basement out, i'm not able to actually go down there and measure right now

thanks!

Anyone have an input suggestions on laying tile with heat based on my previous post? Any input would be helpful!

I didn't gather any specific questions from your last post. Floor structure seems strong enough, set peremeter dams to ensure 1/4" expansion gaps around the room, flange, shower pan/tub, prime the floor, install your heat mats and pour self leveler over top. Install Ditra and then your tile. Post back with anything specific for answers.