New construction subfloor for tile & hardwood

[barbmac]

My first post! We're getting ready to build a house which will have a daylight finished basement with a concrete slab floor and an upper main level with either a truss floor or dimensional lumber joists. The depth of the house is 28 feet. One contractor would span the entire 28 feet with 24" deep trusses while another contractor would use a girder down the length of the house (54 feet) with 2 x 10 dimensional lumber joists resting on the girder. Joist lengths would be 13.5 feet and 14.5 feet since the girder is slightly off-center.

It's the flooring for the upper floor that I'm concerned about. We want mostly hardwood but there is an entry hall and two bathrooms that would get ceramic tile. Since we're able to plan the subfloor in advance, how can we best design the subfloor so that it's stable enough for tile installation but also so that the tile and hardwood floors are the same height?

I looked at the deflecto tool (great idea!) and it appears that 2 x 10 joists will be adequate for tile if they are 12" oc. But ... does this assume there will be ply or backer board on top of the joists? How thick?

Say we use 1/2" ply on top of the joists and 3/4" hardwood. Would we then use 1/2" backer board on top of the 1/2" ply plus 1/4" thick tile to get the tile floor the same height as the wood floor? Thanks!

[cx]

Welcome, Barb.

Given the opportunity to design in advance I'd always plan for a mud bed in the tile areas. That would involve dropping those areas below the adjacent subflooring, then mudding them back up to exactly the desired height come time for tile. Dropping the tile areas 1 1/2" below the adjacent subflooring gives you plenty room for more than the minimum requirement of 1 1/4" of reinforced deck mud.

There are many manufacturer's of tiling substrates who will accept nothing more than a 5/8" layer of plywood over 16"oc joist spacing. I don't like minimum requirements, much, and I like that minimum even less. Not sure why you are planning for 12"oc joist spacing, but that does help in the subflooring arena.

If I elected to have only subflooring and a more contemporary tiling substrate I would plan for a 3/4" subfloor topped by another layer of 1/2" subflooring. Then my CBU or membrane of choice.

My opinion; worth price charged.