How do you stop a toilet from always rocking in a cabin on a lake. The ground is heaving.?

Question

I have replaced the floor and set the toilet and its fine for a year or two but its back to rocking.

Answer 1

sounds like you need  to shim up the toilet and secure the bolts a little better.you may have a leak somewhere too

Answer 2

If it's not leaking from underneath, and the bolts are snug, you can find some small white shims from your local plumbing store. If there is caulk under the toilet at the floor, this will have to be removed. Insert the shims in several places where there is space, then recaulk . This should stop the rocking.

Answer 3

Either the commode bolts need re tightening, the flange is broken, or the floor is rotted.  Hopefully it is the first.