Fitting toilet to uneven floor tricky

Hey there, time traveller!
This article was published 04/08/2002 (8473 days ago), so information in it may no longer be current.

Q. I am remodelling our basement bathroom and am ready to set the toilet. However, the tiled concrete floor is not level. When I test-fitted the toilet it could be levelled with shims on three sides (gap ranges from 1/4 inch to 3/8 inch). Is this a desirable situation or should I strive for more contact between the floor and the toilet? Are there other alternatives? Thank you for considering my question.

A. Shims are one way of dealing with the problem. When using shims, don’t use wood ones. Even under the best of conditions, a bathroom can be a rather damp place and wood shims will promptly rot.

Because your gap is greater than a quarter inch, we suggest the following fix. Put the toilet into place and make a pencil mark on the floor around the base of the toilet. Shim it up with plastic shims. They are usually available in the plumbing section of hardware stores. The outside edge of the shims should be held in about 1/8 inch from the pencil line. Remove the toilet and prepare it for installation by installing one or more wax rings at the underside of the toilet.

Next, mix up a small batch of epoxy mortar. Place a continuous mound of mortar between the outside of the closet flange and the inside of the pencil line — making sure not to disturb the shims. Place a layer of wax paper over the mortar, and lower the toilet into place and anchor it. The object is for the wax ring to seat on the closet flange and for the excess mortar to ooze out. Use a damp cloth (wrung out frequently) to remove the excess mortar, leaving a slight recess at the joint. Once the mortar has set up, use a utility knife with a sharp blade to trim the excess wax paper.

Complete the job by installing a bead of latex caulk over the mortar at the joint between the bottom of the toilet and the tile floor.

–Associated Press