MaryAnnKacz said:
Would the big box stores carry the spacers? If I made one out of plywood, how would I do that, and which would look better?
Here's how I would make the platform:
1. Buy a piece of plywood, the thickness of which matches the space between the subfloor and the bottom of the toilet flange.
2. Rough-cut the plywood so you have a smaller piece to work with.
3. Use a compass to measure and trace out a circle in the middle of this plywood that is the same size as the outer diameter of the flange.
4. Use a Dremel, rotozip. or jigsaw to cut out this circle.
5. Place the plywood over the flange and "dry-mount" your toilet over the flange (without the wax or bolts.)
6. Use a pencil to trace out the base of the toilet on the plywood.
7. Remove the toilet and plywood.
8. Use a jigsaw to make the cut-out.
9. Install platform. Install toilet.
10. Caulk base of toilet to make it look nice.
11. You're done.
I wouldn't worry about the wood deteriorating from water damage. There shouldn't be any leakage if you install the toilet properly. Also, it would act as a shield for your sub-floor if you did develop a leak. And, it's a hell of a lot easier to replace the platform than to replace your subfloor.