Toilet flange and tiling questions

I am new here and don't really know much about toilets. I have a few questions:

1. My husband and I are installing a tile floor in our upstairs master bathroom. The toilet was on 1/2 inch press board. We tore that out, and want to lay down 1/2 inch backer board, 1/8 inch thinset, and 1/4 inch tile. This will raise the floor 3/8 inch higher then it was and I think that the flange is too short. What do I do about that? I could put in 1/4 inch backerboard, 1/8 inch thinset, and then 1/4 inch tile but the floor would still be higher then it was. We want to install a new toilet as well.

2. My other question is about laying the backerboard itself. How close to the flange to I want to lay the backerboard? Does it need to fit snugly, or can there be a 1/4 inch space between the flange and the backerboard. How about a 1/2 inch? Do I fill any space with thinset or caulk?

As it stands now, the toilet is removed, the pressboard is gone, and the rest of the bathroom is prepped and in the process of being tiled. The toilet is in a room of it's own.

Thanks! I hope that this all made sence.

Is your plumbing cast iron, copper or pvc?

Sarah,

I had a plumber cut the old flange off, and leave a "stub out" for me to tile around. I installed backerboard and tile, then installed a new PVC (plastic) flange on top of the new tile. You only need to leave enough space around the pipe for the flange to sit flat on the tile. Takes a little trial and error with the flange in your hand to get the idea. The space was not more than 3/8" all around the flange. If the flange is PVC, it needs to be screwed down to the plywood subfloor, therefore you can't cut the hole in the plywood *too* big. Again, if you have a new PVC flange in your hand, you'll get the idea pretty quickly.

Others may have different advice, but what I have described is a 1 hour job for a plumber, should cost you around $40-$60. Money well spent IMHO.

Ideally, the flange should be on top of the finished floor. It is not uncommon to leave it in place and use a couple of wax rings or to attached a flange extender to raise it up, but it is still better to install it as if it were a new installation on top where it should be.

It is good you removed the partical board, as it is death to tile - it swells up at the hint of moisture, not uncommon in a bathroom! But, before you tile, you need to check out if your subfloor is adequate for the tile or you might quickly be dissapointed by cracked tiles and grout. They have the tools over on that site to check this out and can give you detailed help if you need it.

The backer board (cbu) does NOT add anything significant to the stiffness of the floor, so 1/4" on a floor is fine. Make sure you follow the instructions about using thinset under it and screwing or nailing it properly. Do not use any premixed products - use thinset you get in a bag and mix with water, not the junk you buy in a bucket. Same for the grout. Read a little over at John Bridge, and your tilework will come out fine.