Replies

1. 
   unclemike42 | Nov 18, 2020 10:17am | #1

   This is why tile guys use self-leveling compound.

   You could shim below the flooring, but this would reduce contact between the subfloor and joists to the shim locations.

   I think you will get better results if you glue and screw the subfloor to the joists, then use self leveling compound to get the floor level and flat.

   https://www.finehomebuilding.com/forum/tile-work-self-leveling-compound

   Are you planning an isolation layer under the tile?

   My sister had her bath done, and they used an isolation layer with integrated in-floor heat. (she took out a radiator which was needed when the bath was on the outside wall, but seemed not to be needed after an addition closed it off from the outside)

   https://www.schluter.com/schluter-us/en_US/Floor-Warming/Schluter%C2%AE-DITRA-HEAT/p/DITRA_HEAT

2. 
   pulper_11 | Nov 21, 2020 02:51pm | #2

   Thanks Mike for your reply! Sorry for not thanking you earlier.

   Regarding your reply, I'm more concerned with flatness instead of level. Of course it can't be out of level by a good amount, but it doesn't have to be perfectly level (i don't believe). But, to handle a tile job without the tiles cracking or without lipping, the floor has to be flat. Or, so i've read. What do i know?? lol.

   I do like your idea though of putting down the subfloor first and then making corrections. I think that does sound a little easier than doing it on the joists.
   My plan was to use the 22/32 advantech, then 1/2" durock or other cement board, and then the tile. I have seen the schluter stuff before but am interested in your thoughts on it. I believe that it takes the place of the cement board. That certainly saves on lifting! If I'm doing a small section of my bathroom with heated flooring than this might be an option. However, it's hard for me to make out what it is I need to do this. There are so many options for their stuff and I'm still learning, so that it isn't easy. But it seems everyone who uses it online, after dealing with the expense, really likes it.

   Maybe something like this:
   https://www.amazon.com/Schluter-DHEKRT12056-Touchscreen-Programmable-Thermostat/dp/B00K1I8TY0/ref=sr_1_6?dchild=1&keywords=Schluter+DITRA+HEAT+DHEKRT12040+26.7+SF+120V+Kit&qid=1605988047&sr=8-6

   One question on the advantech. along one of the walls where the tongue would land, do I trim off the tongue from the tongue and groove?

   Thanks again!

3. 
   unclemike42 | Nov 21, 2020 04:35pm | #3

   Last time I checked, level would also be flat.

   You can get flat without level.

   I have not personally used the self-leveling compound, but watched the tile guys do this.

   (when I remodeled my wife's bathroom, my wife did not trust me to do the tile, so we had it hired via the local home despot. they did an ok job, but forgot to put the thermostat for the heated floor in under the tile. We used an earlier in-floor heater, which came in a mesh that was placed between cement board and tile embedded in the thinset. these guys used self-leveling compound, and topped with cement board, and then the tile (over the in-floor heat)) This was almost 15 years ago. I think they bedded the cement board to the self-leveling compound with thinset, but don't quote me on this.

   My sister had her bath done early this year, and they used the isolation layer with the heater I linked to.

   the layout of in-floor heat really calls for a scale drawing, to figure out how to route the wire on the floor, so you get enough. they sell heat elements in certain lengths, and you have to come up with a route for the heat cable that fits criteria. (something like between two and three inches apart, with specified turns and avoiding things like toilets and sink cabinets) You don't have to heat the whole floor. so can put a smaller one where it does the most good for toasty feet. (keep in mind if you use mats, or have slipper wearers in the house, it might not really do any good. My wife started wearing slippers all the time, and the heating in her bath is now turned off. Besides, you already have a great heat duct in the room.) In-floor heat calls for a dedicated circuit, and you can run to either 120 volts or 240 volts.

   You can use cement board over self-leveling if you need more height, or need more stiffness.

   I think the utility of the isolation layer depends on the tile you plan to use. It seems like a good idea to me. I defer to the real floor experts to provide more info. The Canadian home improvement tv star used to swear by it.

   I would cut the tongue off the tongue and groove at the wall.

4. 
   pulper_11 | Nov 22, 2020 01:06pm | #4

   Thanks Mike again!

   No wife here so if I screw it up, only myself to blame (and no "I told you not to do it"). lol.

   One of the links in your previous post was to a discussion on using SLC instead of the cement board. Like you said I could use both if I need added height. Not sure that I will though. Will look into after I learn more about the subfloor.

   the in flooring heat is not necessary but i think i'll do it. my bathroom is only 6x9 and
   i'm planning on a full width shower, so the area heated will not be a lot. therefore, as you suggested, i'll have to do a good amount of planning before buying. one thing i learned by watching some videos is that you can't cut the heating element to make it fit. if you have too much, you have to figure out a way to use it.

   I have watched Mike Holmes use the ditra a lot. i'm assuming that's who you're referring too. i've lived in canada and we have a few good diy people on tv that have also rec'd a good deal of tv exposure in the US. i believe that bryan baeumler also uses an uncoupling membrane too, although i'm not sure it's ditra. it's not cheap but if i look at the kits that include the ditra as well as the heating stuff vs buying all separately, it might not be too bad. and if it works better, then that's great.

   thanks again for your reply. very helpful.

5. 
   ASwissCarpenter | Nov 23, 2020 10:48pm | #5

   I work on a decent amount of prewar houses and I've seen this many times before (particularly in bathrooms where early plumbers went nuts on joists). What we do is pull a string line to find the high and low joists in the plane of the floor. The high ones we snap a chalk line along the side to get "flat" and take the high spots down to the line with a planer. For the low ones, we sister on some 2x stock to match things up with what we planed down. Once its reasonably flat we, fasten down 3/4 OSB with 2" screws every 8". The resulting floor is very solid and much flatter than before. 90% of the time our tile guy is fine with it - sometimes he'll use leveling compound, but its not that often.