I am replacing the toilet in my house, and after removing the old toilet, I can see that the flange is not bolted to the floor. Also, it sits up off the finished floor about a quarter inch. Do I need to add any supports underneath to fill the gap, and do I need to drill holes and bolt it down to the subfloor before installing the new toilet?
Does the toilet flange need to be bolted
flangetoilet
Related Solutions
There isn't much allowance for raised flanges in most US toilets I've seen. The critical feature is how much higher the under toilet "ceiling" is than the bottom perimeter base that sits on the finished floor. Since this dimension is intended to work with a standard wax ring, there's little chance a 3/4" protrusion will work. Not only do you need physical clearance between the flange and the "ceiling", there also must be room for the wax sealing ring.
The other potential conflict is the outlet horn and how it fits into the small bevel of the flange fitting. Again, there needs to be room for the wax to fill this gap. You do not want any direct physical contact between the flange and horn.
Simply supporting the flange is not enough. The perimeter base must be fully supported. If you try to install the toilet as things are, the toilet will be balanced on the wax ring. It will wobble every time it is sat upon, eventually forcing all the wax out until the "ceiling" is bearing directly in the flange. While the wobble will diminish at this point, it will still wobble. The seal would obviously be compromised.
Whatever you do, the perimeter base must be solidly supported. The obvious solution is lower the flange, though very difficult in your case. Another solution would be to raise the floor, which I imagine would be undesirable. The only other possible solution would be to raise the support of only the toilet base, such as setting it on a grout bed. Depending on the nature of your flooring and the actual final thickness of the grout, this may not be too bad a solution. You would need to spend enough time finishing the exposed grout around the toilet base so that it is smooth and easy to clean.
For Future Viewers:
Right idea, but WAY too complicated for minimal support & no screwing for the flange. With NO FLANGE in place, build a frame first, not piece by piece in the floor. With a Flange in place you'd build it without the right side's {bottom} joist attachment so you can dry-fit everything & finish inner attachments to then LASTLY screw to the joists.
Stand up 2x4's to be attached to joists LAST. Then, bridge the Stand-Ups with 2x4's On-Flat. You screw through the Stand-Ups & into the ends of the On-Flats (do just the left Stand-Up {top} configuration if a Flange is in place).
Then, you bridge the On-Flats with a shorter On-Flat. First, screw that in from the left Stand-Up to hold it in place & toe-nail screws on either end at the Flange side. Also, toe nail what can fit On-Flat on the right side {bottom} of the Flange Finish by just screwing outward (& angled upward for this Askers I-beam pictures) through the Stand-Ups & into the joists.
This should be snug to the Flange's underside collar or the drain pipe, depending on your subfloor elevation. The On-Flats even allow you to cut or drill the platform frame for an actual tight fit complete circle. Of course, adjust this proven design to your actual application.
Best Answer
The bottom of the flange needs to be sitting flush with (or not more than 1/8" above) the finished floor or else the toilet will rock. The flange should be fastened to the floor. Dry fit the toilet to make sure it doesn't rock. If it does rock, use shims to prevent rocking - just tightening the bolts probably will not stop the rocking but will risk cracking the toilet or breaking the flange.