How to install a new toilet on an uneven basement floor?
June 14, 2022 7:12 PM Subscribe
I'm replacing an old, cracked toilet. The problem is that it's in the basement and the floor is sloped. Should I level the floor or the toilet?
My 94 year old house had a toilet in the basement under the stairs (it's a thing around here). It was very old and the base was cracked and leaked when flushed, so I removed it. I would like to use the existing plumbing to add a new toilet, which I am not afraid to do myself.
The basement floor is sloped towards a drain in the center, which is nice, but it makes the basement a difficult place for activities. Preliminary measurements with a spirit level show a 3/4" drop from the left side to the right side of a potential new toilet, and about a 1/4" drop from back to front. This seems like too much for a shim to handle.
What is the best solution for potty stability? It's a tiny space, only about 3' by 4', so would self-leveling compound be a good idea? Or should I build some kind of sub-floor on top of the concrete?
I'm not trying to add resale value to the house with this, as it's not even a half bathroom, so any suggestions are welcome.
My 94 year old house had a toilet in the basement under the stairs (it's a thing around here). It was very old and the base was cracked and leaked when flushed, so I removed it. I would like to use the existing plumbing to add a new toilet, which I am not afraid to do myself.
The basement floor is sloped towards a drain in the center, which is nice, but it makes the basement a difficult place for activities. Preliminary measurements with a spirit level show a 3/4" drop from the left side to the right side of a potential new toilet, and about a 1/4" drop from back to front. This seems like too much for a shim to handle.
What is the best solution for potty stability? It's a tiny space, only about 3' by 4', so would self-leveling compound be a good idea? Or should I build some kind of sub-floor on top of the concrete?
I'm not trying to add resale value to the house with this, as it's not even a half bathroom, so any suggestions are welcome.
Best answer: I just finished a project like this. I used floor leveling compound and it worked great. I had to buy a toilet flange extender but those are cheap and easy to find at any hardware store. Put the extender in place prior to pouring the leveling compound.
posted by mezzanayne at 8:17 PM on June 14, 2022 [1 favorite]
posted by mezzanayne at 8:17 PM on June 14, 2022 [1 favorite]
Could you use an extra thick wax toilet ring, then squish down the toilet in an uneven manner that "compensates" for the unlevel floor?
posted by Dr. Wu at 8:39 PM on June 14, 2022
posted by Dr. Wu at 8:39 PM on June 14, 2022
That would really only work if the desired end result is a cracked new toilet with a leaky seal.
What mezzanayne said. Self levelling compound is a product designed for exactly this kind of use case.
Also, if you can get a rubber flange seal kit that fits your plumbing, use one of those instead of faffing about with wax.
posted by flabdablet at 9:30 PM on June 14, 2022 [1 favorite]
What mezzanayne said. Self levelling compound is a product designed for exactly this kind of use case.
Also, if you can get a rubber flange seal kit that fits your plumbing, use one of those instead of faffing about with wax.
posted by flabdablet at 9:30 PM on June 14, 2022 [1 favorite]
Self-leveling is fine if you want to do the whole room, but you could use sand typing compound (4:1 sand:cement) just where the toilet base is, and level it manually.
Self-leveling is a liquid, you'll have to dam the areas you don't want it to go and you'll have a lip at the entryway.
posted by flimflam at 10:28 PM on June 14, 2022 [1 favorite]
Self-leveling is a liquid, you'll have to dam the areas you don't want it to go and you'll have a lip at the entryway.
posted by flimflam at 10:28 PM on June 14, 2022 [1 favorite]
It also includes a polymer component that both makes the thin bit on the most uphill edge less likely to crumble and flake than a simple sand/cement mixture would, as well as improving adhesion to the underlying wonky floor.
posted by flabdablet at 12:33 AM on June 15, 2022
posted by flabdablet at 12:33 AM on June 15, 2022
Measure the distance from the flange to where the toilet will sit and get the correct rubber extension. It's much, much more pleasant than wax. Plus it is more forgiving even when your floor is "level" because the foam will expand to fill the gap, if any. You may need longer bolts, those are cheap, they snap or hacksaw off.
posted by wnissen at 11:35 AM on June 15, 2022
posted by wnissen at 11:35 AM on June 15, 2022
I agree with flimflam. Mix up some mortar and create a level base for the toilet. I would cover the bottom of the toilet with tape, dump the mortar on the floor and push the toilet down on top so that it sits level (may need to be wedged to hold it up if your mortar is a bit thin, but mixing it fairly dry should give it enough integrity to hold the toilet up), screed the mortar off around the toilet base so it only covers the area under the toilet itself then, when the mortar is dry, lift the toilet off and remove the tape. Then just fit the toilet as usual. Think about whether you need to extend the pipe before doing that and you may need longer bolts/screws.
Floor levelling compound is great if you want to level the whole floor and if you want to tile the floor or something, go for it, but think about where you are going to end the level floor and whether that creates a problematic step or water trap. If you just want to fit a toilet and want to keep the current drain in the floor functional, I wouldn't go to the trouble of levelling the whole floor.
posted by dg at 4:19 PM on June 16, 2022
Floor levelling compound is great if you want to level the whole floor and if you want to tile the floor or something, go for it, but think about where you are going to end the level floor and whether that creates a problematic step or water trap. If you just want to fit a toilet and want to keep the current drain in the floor functional, I wouldn't go to the trouble of levelling the whole floor.
posted by dg at 4:19 PM on June 16, 2022
I wouldn't go to the trouble of levelling the whole floor
Neither would I.
I'd use pieces cut from a waxed corrugated cardboard fruit box to make a formwork to define the edge of a base just big enough for the toilet to sit on. I'd design for at least an inch of base extending outward all round the bottom of the toilet, giving it enough meat to stop the toilet breaking chunks off the edge of it under load. I'd also include a little dam around the outside of the existing flange.
I'd use gaffa tape to stick the formwork down to the floor, around the outside of the outer formwork and the inside of the flange dam. Then I'd pour just enough self-levelling compound into the space between the outer formwork and the inner dam to make it end up a little under quarter of an inch thick at its shallowest point.
Once the compound had set up I'd remove the formwork, then chamfer away all the sharp edges with a scraper, then paint it.
Finally I'd use a rubber - not wax - flange seal kit that includes a suitable extender to seal the bottom of the toilet onto the flange.
posted by flabdablet at 5:10 PM on June 16, 2022
Neither would I.
I'd use pieces cut from a waxed corrugated cardboard fruit box to make a formwork to define the edge of a base just big enough for the toilet to sit on. I'd design for at least an inch of base extending outward all round the bottom of the toilet, giving it enough meat to stop the toilet breaking chunks off the edge of it under load. I'd also include a little dam around the outside of the existing flange.
I'd use gaffa tape to stick the formwork down to the floor, around the outside of the outer formwork and the inside of the flange dam. Then I'd pour just enough self-levelling compound into the space between the outer formwork and the inner dam to make it end up a little under quarter of an inch thick at its shallowest point.
Once the compound had set up I'd remove the formwork, then chamfer away all the sharp edges with a scraper, then paint it.
Finally I'd use a rubber - not wax - flange seal kit that includes a suitable extender to seal the bottom of the toilet onto the flange.
posted by flabdablet at 5:10 PM on June 16, 2022
I'd also be happier with a thin and somewhat resilient gasket between the bottom of the toilet and the top of the poured base, cut perhaps from a piece of vinyl flooring or car inner tube. The design intent would be to spread and thereby reduce the most extreme of the crushing pressures that can occur under the edges of something as exceptionally rigid as a toilet when asymmetric loads are applied to the top.
But I would not fit such a gasket if I'd gone against my own advice and used a wax seal, because wax seals are just bad at coping with even very small amounts of repeated movement.
posted by flabdablet at 5:29 PM on June 16, 2022
But I would not fit such a gasket if I'd gone against my own advice and used a wax seal, because wax seals are just bad at coping with even very small amounts of repeated movement.
posted by flabdablet at 5:29 PM on June 16, 2022
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posted by amanda at 8:01 PM on June 14, 2022