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How high should the toilet flange be?

HONewbie's picture

How far should a toilet flange extend above the subfloor?  I am renovating a bathroom that had a mud-bed tile floor, and I am wondering how much I am going to have to build up the subfloor so that the flange will be in the right place after I install my concrete backer and tile.


(post #61542, reply #1 of 20)


Ideally you should remove the existing flange, complete your new floor and then reinstall a new flange screwed through your finish floor.  The flange sits on top of the tile or whatever you are using.

If access is nearly impossible, then try to achieve the same affect with your underlayment height.  However, in that case, you must make sure that when the old flange is screwed down through your new finish floor that you are not putting stress on the waste pipe by forcing it out of alignment.  You'll also need to slide the tile or whatever else under the flange and get a perfect fit.  Not easy or likely.  Better to remove and reinstall.

J. Painter

(post #61542, reply #3 of 20)

The flange is already firmly attached to the subfloor.  I'm not sure how well I can describe it, but the flange is tall with cast-in "bushings" for lack of a better term that the screws go through down into the subfloor plywood.  I'm no expert, but I assume it was done that way so that the flange could be firmly secured to the plywood while still leaving room for the mud bed (1-2" thick) and tile.


(post #61542, reply #5 of 20)


Hmm.  Lets start over.  As I understand it you are putting in a tile floor.  If you were building this new, you would typically have a plywood subfloor over the joists.  Next would be cement backerboard, followed by the thinset and tile.  Once all that is installed, the flange would be installed over the tile and screwed down with brass screws that reach all the way down to the plywood.  (There are some that will say the flange should be level with the tile, but that controversy is settled, I think.)

So, here you are with an existing flange.  The best way to fix this would be to remove the existing flange leaving only the 3 or 4 inch pipe.  That means having access to the pipe to cut it.  (PVC, cast iron and copper all have different issues, of course).  Then you would build your floor as you want, and re-install a new flange on top of the finished height when you are done.  You could hire a plumber to do this for you if you want.  If access is impossible, then the next best thing is to plan your finish floor height so that it comes exactly under the existing but unfastened flange.  Then you would screw it down through the new layers.

If this isn't making sense, then maybe we are missing some information?

J. Painter

(post #61542, reply #6 of 20)

I will try to take some pictures tonight....I think we're on the same page, except for the "unfastened" part.  This isn't a thin flange that sat on top of the tile.  It is a realtively tall piece of cast iron that rests on the subfloor and extends up to a height that was slightly above the previous finished floor.  I have removed all of the old tile and mudbed, and the toilet flange is still firmly planted to the subfloor.

Based on what you are saying, I would add additional layers of plywood such that the finsihed tile surface will be just below the top part of the flange.  Right?

Replacing the drain assembly isn't really an option.  The house is a ranch with a full basement, but the main floor cantilevers out beyond the basement wall by a couple of feet.  This toilet sits out on that cantilever.  The only way to get to the drain would be to tear out the soffit under the overhang, and that's a little more than I want to get into.


(post #61542, reply #8 of 20)

Unless someone here knows exactly the situation you are describing, I am not sure that anyone here can help you. Was the previous toilet fastened to the flange, bolted to the floor or supported in some other way? My advice is to get a plumber on the scene and ask him what to do. If you don't know a good plumber already, you should get to know one. All the plumbers I know appreciate being asked by a diyer how to properly do a job. After all, they will eventually be the ones to come and fix a major screw up. They will be able to tell you how to deal with your problem in less than ten minutes. Whether you will like their answer is another issue.

(post #61542, reply #10 of 20)

You have it right - the BOTTOM of the flange should touch the TOP of the finished floor.  That's the height to build to.  A little low is better than a little high, since the wax ring will take up the slop.  I have even seen a second wax ring used where the flange is too low caused by someone tiling around a flange without bothering to re mount the flange.  Works, but cheesy.

Hope this helps.  Rich.

Hope this helps.  Rich

(post #61542, reply #12 of 20)

Well if you like cheesy...

I had to put in a stool on an old cast iron flange that someone had added a plywood floor atop the old t&g without taking up the old stool. They had cut the ply to fit around the old stool and butted up to the old baseboard. Roar!



(post #61542, reply #13 of 20)

Trust me, the toilet is up!  I didn't have a chance to take pictures last night, but it sounds like I have the answer I need.  I'll probably try to get a picture up tonight just to confirm that this thing is in fact mounted right before I go building up around it.

Thanks for the help, and keep an eye out for a picture.


(post #61542, reply #16 of 20)


Yeah, pictures would be good.  I'm thinking maybe you don't have what we all consider to be a "standard" flange.  Now you've got my curiosity up though!

J Painter

(post #61542, reply #2 of 20)

I'm not sure that you asked what you really want to know. Set the flange at the level of your finished floor. Measure your CBU plus the tile and that's what you want.

(post #61542, reply #4 of 20)

Help me out, what should I have asked?  The flange is already there, secured to the plywood subfloor.  I'm not moving or adding a toilet, I am just redoing the floor around an existing one.  The flange sits an inch or two above the subfloor, and it sat a little bit above the old finished floor.  It was never fastened to the mudbed, it has always been fastened to the subfloor.  I should have measured how much it was above the finished floor before I did my demo, but it had to have been between a quarter and a half an inch.

I hope I am making this a little more clear.  It wasn't flush with the finished floor before, but if that is how far I need to build up then that's what I'll have to do.

(post #61542, reply #7 of 20)

What jpainter said. But what you're describing I believe is not what he and I are calling the flange. The flange is a circle upon which the wax ring sits in the middle. Around the circumfrence are slots on one end of which are slightly larger diameter holes through which you add T bolts to hold down the toilet. Pictures would help because my experience is not enough that the cartoon idea bulb is not going off over my head with your description.

(post #61542, reply #9 of 20)

Bart, you may be able to leave the flange where it is, and just get a wax ring with a neoprene funnel that will allow the water closet to seal perfectly to the waste (flange and pipe) even tho the toilet will now higher than it it used to be. --or-- Could you remove the screws that presently fasten the flange and maybe flex the pipe and flange assembly the 3/4 inch or so up? If it's pvc or copper you may get by. If it's cast iron, better get the plumber we all know we should have called in the first place. Good luck.

(post #61542, reply #11 of 20)

The ideal situation is if the bottom of the 1/4" thick flange is flush with the top of the finish floor (ie, as if the flange were mounted directly to the finished floor). "OK" is anywhere from having the top of the flange flush with the floor up to having it maybe 3/8" proud. If the flange is just flush or below flush then you generally need a thicker wax ring. If the flange is any higher than about 3/8" (depends on the particular toilet) then the toilet won't fit flat on the floor.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #61542, reply #14 of 20)

am I reading this right ...

is your "flange" ... the part that has the holes thru which it's screwed tight to the sub/ply .... thicker than 1/4 inch?

sounds like yours is tight to the subfloor/ply ....

yet the top sits 1 1/2 inch above said subfloor/ply.

if so ...... I've never seen one like that.



Buck Construction, llc   Pittsburgh,PA

     Artistry in Carpentry                

    Buck Construction

 Artistry In Carpentry

     Pittsburgh Pa

(post #61542, reply #15 of 20)

I think it's screwed to the floor through spacers of some sort.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #61542, reply #18 of 20)

Dan, you hit it right on the head.  I just went and took a much closer look, and what I thought was a solid piece is really just what I assume is a standard flange that is screwed to the subfloor through pieces of tube that are being used as spacers.  This is what you get when some dumb homeowner tries to describe something he doesn't know much about.

It is still very solid, so am I okay building the subfloor up so that the finished floor will come just under the flange?

(post #61542, reply #20 of 20)

If the height is right for you, it sounds like this is a good setup. You should try to work mud under the flange to fully support it, of course -- the spacers probably don't provide very good support.

One important thing, when doing a floor in a bathroom, is to get the area around the toilet as flat and level as humanly possible. If the floor is flat enough then you hardly need bolts to hold the toilet down -- gravity will do most of the work. But if the floor isn't flat and the toilet rocks even a little then all the bolts in the world won't keep it from "walking away".

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #61542, reply #17 of 20)

After the toilet is bolted in place, flush it, you should not hear any flushing noise from underneath.  Sometimes the wax ring is not seated, and you will hear it.

Then chaulk the base of the toilet to the floor.  Two brass bolts alone will not hold the toilet down when a 300 lb friend is on it, or when you got a leg braced on the wall.  SOme will not chaulk the back to see if the wax ring is leaking, but it wont leak if the base is chaulked so the toilet dont rock.

(post #61542, reply #19 of 20)

Thanks for the advice, I will definitely do that.  I'd hate to tell Bertha that she can't use my toilet.