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sagechickie 04-17-2009 10:51 PM

what substrate to use?
i want to remove a sheet vinyl floor in a bath and replace it with ceramic or porcelain tile. When we remodeled this bath 10 years ago, we put a particle board subfloor in over the original floor because of bad areas where the toilet and sink were. the floor in the adjacent hallway and living area are the original red oak flooring which we had refinished. My question is, will i need to remove and replace the subfloor with cement board? If i go over the wood subfloor it will make it quite a bit higher than the flooring in the adjacent area. any suggestions?

Just Bill 04-18-2009 06:22 AM

Ceramic tile requires a VERY rigid floor, min 1 1/4". If it is not rigid/stiff, you will have cracking tile and/or grout. If there is still particle board, get rid of it, it makes a poor substrate for tile. What is the subfloor?? Usually 1/2 or 3/4 plywood. If 1/2", add another layer of 1/2" glued screwed to the first, with seams in different locations, then add 1/4 duroc or hardibacker set in thinset and screwed. If 3/4 subfloor, add 1/2" backer as above.

The biggest probelm with adding thickness to a bathroom floor is raising the toilet flange. It should be flush to 1/4" above the finished floor.

sagechickie 04-18-2009 08:38 AM

i misspoke about the subfloor. It is OSB over plywood and not particle board. We put that in over the existing bad subfloor. I can deal with the toilet flange issue. my concern is that i will have a large offset between the bathroom floor and the adjoining hardwood floor in the hallway after the tile is in, especially if i have to put the cement board over the existing substrate.

jaros bros. 04-18-2009 09:45 AM

Strip down the unnecessary layers and damaged layers. Make sure you stagger new underlayments. Without knowing your joist size and spacing no proper determination can be made for required layers. Sometimes 3/4 alone is sufficient but not always recommended. 3/4 plus 1/2 is great. Think about using Ditra. It's a lot thinner and has a much better record than cement board.

sagechickie 04-18-2009 06:46 PM

Thanks. i'm not familiar with that product but i think i know what it is. The subfloor is sound, i'm certain. this bath was remodeled about 10 years ago and i'm confident it is structurally sound. I am just concerned about the additional height off the adjoining floor if i have to put this cement board-type stuff down on top of my existing floor. There will be close to an inch or maybe more, of height difference.
Also, is it recommended to take out the cabinets and put the flooring under there? These are quality base cabinets.

ccarlisle 04-19-2009 07:49 AM

The cement board recommended for floor is only 1/4" thick...1/2" goes on walls and neither offer any real structural support. Ditra is another 1/4" tops - so you have room.

sagechickie 04-19-2009 09:04 AM

ok i get that. add another 1/8 for the tile on top of that and there is 3/8 plus the 1/2 from the subfloor we put under the vinyl.
Nobody has told me how to deal with the big offset between this new flooring and the adjoining original floor level in the hallway.

ccarlisle 04-19-2009 10:01 AM

You mean you need more height? Just add 1/2" underlayment under the Ditra.

jaros bros. 04-19-2009 12:44 PM

You will have to put a tapered threshold in.

sagechickie 04-19-2009 01:38 PM

I don't need more height! i have more than i want. Are tapered threshholds easy to come by? or do they have to be made? The guy who refinished my oak floors made one for the transition to the kitchen floor which is higher also and for the same reason.

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