5/8 CDX is a good standard grade for subflooring. However, under either hardwood or tile, I would recommend that a floor should be two layers of 5/8 T&G plywood screwed and glued. For hardwood, this provides a needed high-grip nailing substrate that will lead to much fewer problems with squeaks down the road. With your 1^12 subflooring, one layer of 5/8" t&g screwed and glued is fine. For tile, if you do not want movement and grout cracks, you need a very rigid substrate. If the tile is for a wet location, I would cover your subfloor with of 5/8 or 3/4 inch T&G plywood with 3/8" or 1/2" of concrete backer board above it-- again screwing and gluing all sheet goods is really important. As long as you maintain the minimums, you can adjust materials thickness to achieve a match of finished flooring. For example: 3/4" t&g + 3/4" oak matches 5/8" t&g + 3/8" concrete board + 1/2" tile very well. As mentioned above span of the 2^10s is important. For anything over 12 feet, 2^12's or 12" TJI's are called for to prevent bounce. What is important is not the size of your room but the span of the floor joists which you can determine by going into the basement or crawl space. Of course your statement about 1^12 subflooring makes me think your house is old. If that is the case the 2^10's may actually be much stronger than today's are.** One thing that confuses me, however, is that plank subflooring was normally laid diagonally to provide better shear resistance and to allow normal layout of the finish floor. With the way your subflooring is laid, you really need to use plywood above, since otherwise you may be tempted to lay the flooring parallel to the joists to avoid ridges in the hardwood at the joints between planks-- that would be a really bad idea. Will ** The roughsawn 2 by 10s in use 100 years ago are actually twice as strong as today's 2 by 10's if made of the same wood species since the bearing strength of a joist is proportional to the square of the thickness and the cube of the depth of the joist. (2/1.5)**2 x (10/9.5)**3 = 2.1

When we go a front loader I read of problems some of them had on anything but a concrete basement floor. We had a carpeted sub floor on a crawl space with normal joists. To improve stability I merely cut a 4x8 piece of A-C grade exterior plywood to fit under both the washer and dryer. i figured it would srpeat tha weight over more joists and add stability. We had it installed over the very short napped carpet with ring nails and then put a Hardy board underlayment on both the rest of the carpet and our "island". Then we had porcelain tile installed. This has worked just as we expected and is doable and cheap.

Engineered is real wood and if you look around, you can find unfinished engineered, so you can have it finished in place and not have the bevels if that is important to you. I didn't look at the videos provided so this might have been covered but here in Texas almost all houses are built with slabs at grade level and most of the new ones have wood on the ground floor.. There are several acceptable ways to do it: Plywood subfloor nailed to concrete and solid wood nailed to that (solid wood probably not as good in your case, these slabs all have vapor barriers under the slab, which you won't) or engineered glued to the plywood subfloor Engineered wood glued to slab (do a calcium chloride or other approved moisture test first) Vapor barrier and engineered wood floated over that. Many of the engineered woods allow floating installation, you have to glue the tongue and groove together. Different products are labeled for different types of installation, you have to be sure to check what they are labeled for. Find a reputable, knowledgeable NWFA installer, get them to do the moisture tests (the glue down a piece of plastic is not considered reliable) and then have them spell out your options. Now guess how I know all this? :-)

Apologies if this is thread highjacking, but this discussion struck me as the most appropriate for this inquiry. When we were taking bids from contractors for our new construction house, one of the contractors specified a mud job for the master bathroom (both floor and shower) and kitchen/mudroom and Schluter Ditra for all other bathrooms. In talking with a tile installer at a flooring store this past weekend, he said he couldn't think of a situation in new construction where a mud job (as contrasted to Ditra) would be appropriate. Is that right? We're not likely to be using any natural stone but we will likely be using large format porcelain (or possibly ceramic) tiles in some of the bathrooms (12x12, 8x24, etc.) We will have electric radiant heat pads in the floor of two of the bathrooms and hydronic radiant heat in the kitchen and mudroom. We're flexible at this point and want to do whatever will make the installation safest and sturdiest for the long run even if it costs a little extra at this stage. Thanks in advance for any advice.