Shims/uneven floor causing leak?

Help! Every time I flush my toilet, it leaks. I'm in a condo, above a storage room so luckily no on lives beneath me. I had this problem looked at a year ago, and they replaced a wax seal and put a little wood shim under the toilet. The toilet is on an uneven slate floor, and so not completely flush.

It just started leaking again, and I'm not sure what to do. The wood shim has loosened up and isn't doing anything to help. Is it possible to fix the problem by simply wedging the shim back in and stabilizing the toilet? Or does the toilet need to be reset?

And - should I call in a plumber as well as someone who can perhaps cut the slate out around the toilet? Is there any other way to fix this that wouldn't require carving up the floor?

Help.. and it's the only toilet in my place, so this is somewhat of a problem!

A toilet flange is supposed to set on top of the finished floor. The wax ring (or the waxless ring) if fitted to the horn on the bottom of the fixture so that when the horn is inserted into the flange, the sealing ring forms a tight seal between the toilet and drain. Two tee bolts in the flange secure the toilet to the flange. Sometimes a floor is not perfectly level, so it must be shimmed to prevent the toilet from moving even though it is bolted down. That's all there is to it in a perfect world. Unfortunately, we don't always have the perfect world. If the current floor was laid after the flange was secured to the drain, it could be sitting lower than the surface of the floor which could require 2 wax rings. The fact that the shim is no longer working lead me to believe you should pull the toilet and see just where the flange is resting. After cleaning the old ring off, try setting the toilet on the flange without a ring and see what shimming is necessary. Then install the toilet with a ring or rings and apply the shims as your test indicated.

If the toilet moves at all once installed, it will eventually cause a leak. You may need to stabilize the shims, plus, some of the wood shims are quite soft and will compress, or change size with the seasons slightly. Some peole use a penny, dime, nickel instead of a wood shim. You might also want to put some caulk around the toilet once you get it stable - the caulk should hold in your shims and prevent any misses from getting under the toilet. My unprofessional opinion.