bathroom remodel toilet flange and subfloor question

[krogers]

I am remodeling a small half bath. Demolition removed the tile, mortar backing and 3 inches of cement. Very old house, so there is no subfloor. I am putting in a 3/4 subfloor and then durock cement backer board and then tile. My question is about the toilet flange. Does it need to be supported by the subfloor or backer? The flange is cast iron and one piece connected to the drain pipe. Can I drill a hole large enough to fit over the flange and drop the subfloor over it? This would leave the flange unsupported by the subfloor. I could then slip the durock under the flange in two pieces.

Also what should the finished height of the flange be? Is it flush with the finished tile floor, or should it be above it? Thanks in advance. - Kevin

[master53yoda]

you need to put the sub floor under the flange or the toilet weight will set on the piping instead of the floor. the top of the flange needs to be within 1/4" of the finished surface of the tile. ?? is the toilet flange in good enough condition to use or does the flange need to be replaced. I would think that if it is that old you may be better off to replace the ;flange etc after the sub floor is installed.

[pecker]

The flange should sit on top of the completed floor, if possible. There should be holes in it to attach it to the floor beneath it with screws. If you don't have anything solid to drive the screws into, the whole assembly may flex up and down in use.

As long as you don't have a 350 pound brother in law coming over, it will probably maintain a seal, though.

I'd be concerned that if it flexes much, over time, the cast iron might crack where it joins the main waste line.

[conwaygolfer]

Toilet Flange

If you use a sawsall and cut the cast iron flange off, you can then use a "Fernco" fitting to reattach a new PVC flange to the old cast iron pipe. If you can cut the cast iron pipe low enough, attach the fernco and then a small section of 4" PVC pipe into the fernco. After you install the subfloor, just glue the new PVC toilet flange into the 4"pipe to set and screw it into the new subfloor. It is quite easy as I do it all the time.
Glenn

[pecker]

If you use a sawsall and cut the cast iron flange off, you can then use a "Fernco" fitting to reattach a new PVC flange to the old cast iron pipe. If you can cut the cast iron pipe low enough, attach the fernco and then a small section of 4" PVC pipe into the fernco. After you install the subfloor, just glue the new PVC toilet flange into the 4"pipe to set and screw it into the new subfloor. It is quite easy as I do it all the time.
Glenn

When I had to do this, I was able to cut off the old flange and pipe, just an inch or so below the subfloor. The BORG had a PVC flange with a slightly undersized stub coming out of it. There was a neoprene seal around this stub. You just slid the whole thing down into the cast iron, then fastened the flange to the subfloor. Something like this:


Cutting that cast iron with a reciprocating saw was a real PITA, though.

[conwaygolfer]

Toilet Flange

When I had to do this, I was able to cut off the old flange and pipe, just an inch or so below the subfloor. The BORG had a PVC flange with a slightly undersized stub coming out of it. There was a neoprene seal around this stub. You just slid the whole thing down into the cast iron, then fastened the flange to the subfloor. Something like this:


Cutting that cast iron with a reciprocating saw was a real PITA, though.

I did not know that was available. Next time I do one, that looks like the route to go. How far down into the old pipe will the new tail piece go? Is there much room for error? (not that I ever make them - HAHA)Thank you.
Glenn

[chopnhack]

For what its worth, for the couple of bucks that the 4" fernco costs, its well worth it to know that even if the cut on the cast pipe are off (which they will be cutting at an angle) the fernco will still seal everything in. It might be just me, but I would be uncomfortable knowing that that short stub was all that was between me an a ruined weekend!

[krogers]

Thanks for info

I have said it before, but I will say it again. I can always count on you guys for ideas and help.

So based on your advice, these are the steps I am going to take:
1. Cut off old flange and cast iron pipe just below the new subfloor.
2. Install 3/4 ply subfloor with 4" hole over cast iron drain pipe.
3. Install 1/2 durock over subfloor with 4" hole over drain pipe.
4. Install new flange in drain pipe, screwing the flange to the durock and subfloor.
5. Tile up right up to flange.

Sound about right to everyone? The floor tile I am using is only about and 1/8 thick. And I am assuming that the flange doesn't rest on the tile. That would make screwing down the flange through the tile difficult. I did see some pictures on the net with the flange on top of the finished floor, but I think that flooring was vinyl and not tile. Tiling close around the flange would make the flange flush with the finished floor.

[krogers]

Here is a picture of the flange and pipe.

[krogers]

one more question..........

I thought the rough in for a toilet flange was 12". This was and old 5 gal flush toilet that I pulled out. The center line of this pipe is 16" from the studs of the back wall. Is that going to be too far out from the wall for a new toilet? I have the toilet in a box. I will get it out and check the distance. But I thought one of you might know the answer. I might need to move the drain pipe and vent that is attached to it.

[pecker]

I did not know that was available. Next time I do one, that looks like the route to go. How far down into the old pipe will the new tail piece go? Is there much room for error? (not that I ever make them - HAHA)Thank you.
Glenn

Sorry, I don't recall the length. It was probably intended to be used where the old cast iron had an ear broken off, or a new floor would raise the height too much to get by with double wax rings. I don't think cutting through the whole waste line was part of the plan...too much work for most people.

When I cut mine, I tried to get it just below the point where the underside of the subfloor would end up being (the subfloor wasn't installed yet) You might could go an inch lower, but not much more.

[pecker]

I thought the rough in for a toilet flange was 12". This was and old 5 gal flush toilet that I pulled out. The center line of this pipe is 16" from the studs of the back wall. Is that going to be too far out from the wall for a new toilet? I have the toilet in a box. I will get it out and check the distance. But I thought one of you might know the answer. I might need to move the drain pipe and vent that is attached to it.

12" on a modern toilet usually just clears the wall behind the tank. 13" gives a little extra room too clean, or when you need to repaint in the future. But 16" is gonna look a little weird.

Maybe just build the wall out a couple inches. Or cut off more of the pipe and replumb it with modern fittings, like a previous poster suggested.

[JimD]

Instead of having the gasket on the toilet flange, you can also just cut the pipe and use a rubber coupling from the cast iron to PVC pipe and attach the toilet flange to a short piece of PVC pipe. I would do this if it was cheaper or if it allowed me to get the toilet where you want it.

I also think 16 inches is a bit much.

I would probably just screw the flange to the subfloor, however, instead of to the cement board and the subfloor. The cut edge of the concrete board I have used has been pretty crumbly. If it crumbles under your flange, you just lost support. You could mash some thinset into it during tile installation, however, to try and stabilize it. Flange height is not very critical as long as it is not too high to allow the toilet to sit on the finished floor. You can use multiple wax rings if the flange is on the low side (but it is better to get it right). The top of the flange being flush with the finish floor is what I have aimed for when I did this. If you put a straight edge across the bottom of the toilet, you can measure how high up from that the waste opening in the toilet is. It's probably on the order of 1/4 to 1/2 inch - which allows for the wax ring. The rings start out about 3/4 thick. I would rather have another layer of plywood under the flange if necessary to get it to the right height than the cement board.

Jim

[krogers]

Good idea on the crumbling cement board under the flange. But I don't want to screw the flange to just the subfloor. Adding the 1/2 cement board and tile around the flange would leave the finished floor 3/4" above the flange. That seems to be too much. So how about adding a wood ring to the sub floor? A wooden ring out of 1/2" ply would bring the flange up to the correct height. And I could glue and screw the ring to the subfloor. What do you think?

[crokett]

The closet flange ideally should sit flush on the finished floor, or at least on the backerboard with tile around it. If it is rececessed into the floor there are wax ring extenders that take up the gap to the toilet. I would not put the flange just on cement backer board. It needs to have the ply underneath it for support.