You can have the same flooring throughout...you just have to accept a tiny transition strip between the two floors. You can use cork underlay (3mm) on the wood side of the house to lift your new floor 'up' to match (or come very close) to the level of the concrete. That allows you to use a regular 'T' moulding.

Have fun.

Thank you. Are planks orthogonal to the step as in my figure out of the question if everything is made level? I really would love the open floor effect

It is intensely difficult to get a new concrete slab and an old floor to sit level. The concrete has to be poured that way...and the old wood floor has to be pulled and made level.

To do this the way you want, you would have to put down a new subfloor over top of BOTH. Who is doing the work? And how much ceiling height to you have to lose?

3mm Cork underlay = $0.39/sf. The T-moulding = $15/linear foot.

Cost of a new subfloor = $5/sf.

It's your call. What type of budget do you have?

mmm I had 2 installers that came over and said they can do it without transition just by making the wood subfloor level with the concrete subfloor. One said that for tiles he would bolt 1/4 concrete boards over the old hardwood that is on top of the wood subfloor. And then use mortar to smooth out the 2-3 mm transition between concrete and wood subfloor. No transition tiles needed on the opening he said. Should I trust this?

Is one of these the same guy who told you no problem on the pool table or the cabinets directly on a floating floor?

^^^HA! Snap! Millworkman hits it on the head...AGAIN!

Your 'dude' (sigh...I'm telling you the guy with 2 years of experience has yet to have a MASSIVE fail that costs him his HOUSE!) is not making allowances for the gap (vertical gap....between the old house and the new house = gap between the wood and the concrete). That gap is going to move.

Actually it isn't the gap that moves...it is the WOODEN side of the house that moves. Wood expands and contracts in the presence of moisture. That means between the seasons that gap will expand (in the dry winter months) and contract (during the humid summer air).

Tile is NOT happy with this type of expansion and contraction. There will be issues with tile in the breeze way. I guarantee it. I would get this in writing.

It will say, "I, Joe Schmoe floor guy with 2 years of experience, hereby promise to remove and replace all flooring that fails because of my installation technique. I promise I will not leave the town, state or country upon notice of complaint. I will guarantee my work for five (5 years). After such time I will offer prorated discounted repair service for the next 10 years should this floor fail due to my installation techniques."

I can guarantee the installer will not agree to this. Because several hundred square feet of failed tile work could bankrupt his little business.

This only works if you FLOAT a wood over a FLOATING wooden subfloor like Dricore ($1.35/sf + $1.65/sf labour = $3/sf). This STILL REQUIRES the two floors to be leveled out. This is a MAJOR renovation to get your vision to work.

Again, you've been given the limitations of your situation. What you 'want' is not something your budget NOR your installer can handle. Go ahead and get 3mm cork underlay over top of the wooden floor...now float a wood floor over the concrete and over the cork. You will have to leave drop in a T-moulding at the gap...and you are DONE. This is what the HOUSE is able to do.

Just because you 'want it' doesn't mean it is feasible. You could spend $10/sf on this area. You could hire a TOP flooring pro - not a well meaning 2 year pro. You could also shrug your shoulders and say, "Nah. I'll just to it the way the HOUSE wants it done. It's easy and FULLY ACCEPTABLE in the world of design and flooring."

Go ahead and ask your installer, point blank, if he can AFFORD to pay for a complete redo of your home's flooring WHEN his plan fails???? If he looks shocked and angry, you know the answer is "Hell Naw!"

You can swim upstream against the current and curse it every time you have to paddle harder or you can float with it and end up on the other side without any physical (or financial) exertion at all...other than keeping your beer from falling off the inner tube!

It's your call....but the house has spoken.

I got another guy over yesterday, 14 years of experience. He said it can be done with no transition (tiles or wood orthogonal to the door). Honestly, I am with you, it seems very weird that tiles would last that way. I guess here in Gainesville it is hard to find a good installer. I have a 3rd one coming over on Monday and I see what he says. Both the installers who came so far (the 2-year and 14-year guys) said that using a backer board over the subfloor transition wood-concrete (after made level) will be enough to withstand wood expansion and a few mm of differential settlings. They said no problem for sure with floating wood running over concrete and hardwood (made level). Again I am with you, you convinced me, it seems strange to me that subfloor and old hardwood expansion would not cause damage to tiles. I am not sure about floating wood though. Can you convince me? (always talking about going orthogonally and continuously with planks as in my figure with no transition). Thank you very much for your invaluable help, I think this post and your suggestions will be of help to many people with the same type of subfloor combinations.

I would build up the lower wood subfloor and apply patch compound to smooth out the transition between the two spaces. Glue down the engineered flooring on the concrete side and nail it on the wood side.

"G & S Floor Service", are you saying that by using a flexible patch compound I can go orthogonally to the door with the engineered planks? What about tiles, can I do it with them (using staggered concrete backer boards orthogonal to the door)?

The patch compound needs to bond and not flake off. The wood floors will need to be stripped of the finish to bare wood. The existing hardwood floors also, need to be fastened down and stiff. You would use a quality silane base flooring adhesive for it's flexibility. Glue to the concrete and patch compound. If, the patch compound is thin enough you can nail it.

I cannot answer for tiles, not a tile expert.

An update: I finally went for 8" wide white oak, rift and quartered, select, 4 mm wear layer. The installer just made the wood subfloor level with the concrete slab by removing the old solid hardwood and adding a moisture barrier plus 3/4" plywood. See picture below, not wood subfloor is just 1-2 mm lower, and he said he will grind progressively the concrete slab to make it level (it is higher close to the transition anyways). He will glue everywhere. He sees no problem with having the planks running perpendicularly to that transition line between concrete and plywood. The only thing I can think of is vertical thermal expansion of subfloor or differential subsidence, but I think the latter is unlikely, and the first minimal. What do you guys think? The install will be under warranty, I need to ask for how long and to have it written down.