It's Monday in Vancouver and a long weekend. I thought I would try calling Schluter Head Office USA and ask my questions on this new install I saw featured in Mike Holmes magazine. Schluter Systems L.P. 194 Pleasant Ridge Road Plattsburgh, NY 12901-5841 Tel.: 1-800-472-4588 Fax: 1-800-477-9783 I called and was transferred to Paul in Customer Service/Tech Support. I asked Paul about the installation and described it to him. Paul told me that Schluter does not have a rating for the use of Kerdi Board for floors. Paul added that they won't anytime soon. Before I called Schluter I gave Nu Heat another call and as luck would have it got a hold of Ava working the long weekend shift. Ava was not aware of any private testing with Kerdi Board but suggested I call back tomorrow and speak with Pat Mann. Pat I'm told is the guy with all the answers. Ava suggested I ask Schluter for a fire rating with the Kerdi Board. Ava told me that if Kerdi Board is rated for 88 degrees Farneheit (82 F for laminates) we would be OK. I asked Paul at Schluter about the fire rating of Kerdi Board and was told that it is not yet rated - and no ratings are available at this time. Looks like to me that this "Showcase" of building bathrooms better is a "Concept" and one yet backed by Schluter International. The R&D team at NuHeat tests their product with all of the industries top products and Ava told me that 1/4" cork is one of the best products to use with their heating system. 1/4" cork. That's what is installed in my basement. I'll call Pat Mann of Nu Heat tomorrow and get some more insight. Perhaps Nu Heat can do the testing for Schluter on the Kerdi Board and speed things up. JW John Whipple North Vancouver

You don't need to insist for it to be installed on the ceiling. The only time it's be required would be for a steam shower where all six sides of the shower cube would need a barrier. For a tub surround it's perfectly appropriate to Kerdi the walls and just paint the ceiling. If you want to tile the ceiling, then you could Kerdi and tile the ceiling, or cement board (no Kerdi and no green board) and tile the ceiling. To seam Kerdi, one sheet can overlap another (2" minimum for any overlaps) or the sheets can be butted together and then the butted seam covered with a strip of Kerdi or a strip of Kerdi Band.

MDLN, in our first shower we built, we did not use any membrane. We had leakage issues that were surprisingly solved by sealing all the grout. But for awhile I thought we were going to have to tear it out and start over. This time around we are layering tile, redguard, durock, original plaster Here is a link that might be useful: Greenboard - not for showers!

Everything always has a bit of natural "drying" ability. Spill a little water on your floor and it'll evaporate. Set up a slow drip and if the rate of accumulation outpaces the rate of evaporation you'll end up with water damage. Same with moisture in house walls. Moisture vapor can be driven into wall assemblies, mostly via air movement. Some insulations are better at restricting air movement than others. Foam and dense-packed cellulose are great air infiltration barriers, fiberglass is not so good. When moisture vapor does get into walls, some wall assemblies can "hold" the moisture better than others. Cellulose can hold moisture fairly well, fiberglass insulation not so well. Same with liquid moisture. Liquid moisture can get into walls via a leak in the plumbing, cracked grout, a roof leak, etc. When moisture gets into an assembly, it needs a way to escape. It usually escapes via the same path it entered. Moisture is accumulated during a wetting cycle, and given up during a drying cycle. If the wetting exceeds the drying, then over time you get water damage. Rot, mold, etc. Building science generally recognizes the idea of wetting and drying cycles. It recognizes that some materials hold moisture better than others. It recognizes that moisture may get into assemblies. Because of that, we also want to provide a back door through which it can escape in case it can't exit through the way which it entered. That's why building code prohibits two vapor barriers in a wall assembly. Moisture that gets in could be trapped between the two barriers, creating what's referred to as a "moisture sandwich." There's a way in but not enough of a way out. I certainly understand there are all sorts of "but what if..." and "but how could it..." on this subject. But that's the short long answer. The long long answer is really long...and evolving. Just like building science.