i'm about to put down the tile on my floor and was wondering if its appropriate to put the toilet flange on top of the tile (as opposed to on top of the cement board). the flange i have is a pvc base that fits inside the 90 elbow, with a metal flange.

the flange will fit either way, i just don't know how i'd screw down the flange if i put it over the tile.

thanks in advance

 

You can put the flange on the cement board. You didn't say how thick the tile is. You can always use a flange extender if it will be too low in the floor. These have an adhesive and then are screwed down using the holes in the existing flange. They come in 1/4" thicknesses and can be stacked if necessary. Good luck.

 

I'd recommend below the tile on the backing surface. If it's flush with the floor and the top of the tile comes about even with the top of the flange, this gives you the proper clearance for the wax seal between the toilet spout and the flange. If it ends up a little low because of thick tile, you can always install an extender as previously recommended, and there are double-height wax seals as well. I would also recommend using a wax seal with a urethane sponge on the inside, it tends to seal the gap better in my experience and resists oozing in super-hot weather over time.

Having completed this same job not too long ago, I discovered a few pros and cons. The previous owner, some decades ago, installed the flange way too high, on top of tile, over linoleum, over tar paper, over the original fir floor. So when the insufficient gap between the spout and the flange squeezed out all the wax from the seal, I was left with a little chamber of funk to capture the splashes and run them between the various flooring layers. To compound matters, the toilet was sealed completely at it's base, so there was no indication from above that there was a problem. Only when I decided to replace the toilet with a taller model to accommodate my 6-1 frame did I discover the horror underneath, as 12 inches of tile on all sides came up as I rocked the toilet loose. I screamed so loud when I saw what I had to deal with, that my housemate came down to see if I'd just cut off a finger.


The lessons I learned were thus: better too much space than too little, you can always use a spacer or a thick seal; if you choose to seal the outer perimeter of the toilet, leave a little gap at the back so if there is a leak, you'll detect it before there's extensive damage; trying to drill holes through floor tile will kill carbide and diamond bits, it's much harder than wall tile; a diamond wheel either on a tile saw or on a Roto-zip makes quick work out of the floor tile when cutting the tile to inset the flange on the backerboard or subfloor; and finally, an annual crawl under the house to peer up at your flange (if accessible) is worth dealing with the spider webs.

One last recommendation: use the biggest appropriate screws to fasten the flange to the floor. The tilting of the toilet puts a lot of torque on the flange, and if the toilet is allowed to rock, this will eventually work loose the seal and cause leaks. There are plastic wedge shims available that you can use to level and snug the toilet if necessary, but make sure not to tighten the toilet to flange bolts so tightly that you risk snapping the toilet.

I hope my experience can come to some good by helping you with your project.

--Karl

 

great info, thanks for the responses. unfortunately i was very impatient and i laid the tile before reading your responses (my project is going on 3 weeks at this point, and its our only bathroom).

i think my only problem was that when I inserted the flange into the waste pipe, it was too high to sit flush with the cement backer. as it turns out, the tile fills the gap perfectly, so i installed it on top of the tile, and it is flush with the floor. the tile isn't particularly thick, its 1" octagons, (i'd say its about 1/4" thick?).

i will definitely leave a gap behind the toilet to monitor any issues. the bathroom is on the 2nd floor, but I do have access to directly underneath the toilet, so that will give me another way to keep track of it as well.

if there are issues, will i know right away, or is it possible that issues with installing the flange this way won't manifest until later?

thanks again...

 

Good for you for grinding through the job. (I think I spent over 3 months with a hole in my floor, as my tile was extremely old, irregular and impossible to match, so chiseling old adhesive off of 117 tiles wasn't exactly a quick walk in the park.) I applaud your decisiveness, a toilet isn't exactly a wait forever job much of the time.

From the flange you describe, I think its height is a little slimmer than the plastic jobby I used to mate to the old cast iron sewer, so you should be fine. I can only speculate that if there were an eventual leak it would take a while (Unless you are flushing Niagara falls directly into an elbow to generate considerable splashback, in which case it would be more apparent). But I think your lower profile flange will work like a champ.

I would still recommend you use the wax seal with the embedded polyurethane gasket, it has come highly recommended and should just about eliminate any likelihood of leaks. make sure you set the toilet straight down on the seal (not at an angle), and then push down evenly with your hands parallel and in line with the flange bolts. You can then carefully sit your body weight down at the rear of the seat in the same place, and that will seat the toilet nicely.

I hope this reply is still timely enough to catch you before the job, but it sounds like you are right on track regardless.

Cheers.