Need suggestions for how to level subfloor for tiling!

[Powers]

Hi all,

I'm in need of some help to make sure I properly prepare and underlayment for new bathroom floor tile.  My only problem is I'm not exactly sure the best way to get the floor level and ready for tiling.  I live in a 90-year old house, and there are some interesting quirks to this subfloor that didn't come up in any youtube tutorials.

You can see from the first attached picture that instead of having wood planks on top of the joists, they are just butted up against them (see the two 2" pieces running perpendicular to the rest of the wood)

Those two vertical pieces are slightly higher than the rest of the wood butting up against them. From that high point, the floors start to dip down to the left and right back by the tub. Additionally, there are a few imperfections you might have already noticed -  like a small hole by the toilet flange (2nd attachment) and a pipe with random pieces of sheet metal that apparently doesn't go anywhere (3rd and 4th pictures).

I am planning to put down some plywood over this to begin tiling. What should I do between the plywood and this uneven subfloor? Should I ignore that hole because it is so small? Should I shim up the plywood at all of the low spots? Maybe just put the plywood down then put self-leveling compound on top of that?  How would you address this?

Thanks for any help you can provide!

[Joggernot]

I used self-leveling cement.  Works great; just make sure you get more than you think you'll need and mix it per instructions.  Will also level out the floor around the toilet so it sits level.

[Greg]

In a case like this you'd be best served to re-frame that area and install new 3/4" or thicker subfloor, then 1/2" cement board, then your tile system.  I say "system" because you may want to look into system like Schluter.

If you can't or don't want to reframe it, I'd recommend 3/4" to 1-1/8" plywood, glued and screwed to the existing materials. For best results you'll probably want to remove the baseboard to provide access to the edges.

The idea is to create a very stable and strong underlayment for your tile work.  If you work over something too flexible, the tile work will fail.

[sleepyguy]

That's a small enough area that it will be super easy.  Pull up old stff and SCREW down 3/4 plywood.  Make sure the build up is correct to stay level with the outer flooring.

I had to do the same but for an ENTIRE floor before I laid down hardwood!  Haha that's what happens when you buy a 1960s place :)

[Boz86]

Good info here, just for future reference there's a great tile forum: http://www.johnbridge.com/

[Bourbon]

Good info here, just for future reference there's a great tile forum: http://www.johnbridge.com/

Second this. 

[paddedhat]

Thanks for that first pic. Thirty years of swinging a hammer and I never saw anything like that. My take on it would be to sawzaw all that short crap out of there, then start again. I would hit the tops of the joists with a palm sander and some real aggressive sandpaper to clean them up, then glue and screw a new layer of 3/4" T&G subfloor plywood. Next would be the bright orange Ditra isolation membrane. Now you have a tile substrate that will perform well for the next 90 years.

[former player]

Looks to me like someone made this bathroom by taking out an original wall where the middle of the room is and then taking a strip of each room to the side to make the bathroom.  But however it happened, tiling over it isn't going to work.  Personally, I'd take the easy route out and get some very good quality cushioned linoleum: this method has the added benefit of preserving the archeological history of the house.  But if only tiles will do, I'd take up the lot and start again, and this does have the added benefit of being able to check whether there is any rot underneath that collection of problems.