You can add another 3/4" plywood for a total of 1.5" of total subfloor thickness. With a total thickness of 1.5", you can pretty much do as you like. The deflection rating of the floor is determined by 2 things: Distance between joists (measured "at centre" to keep things simple) 2. Total thickness of subfloor elements A proper subfloor is at least 2 layers. If you have a single layer of subfloor/underlay, then you probably have to lay new plywood anyway. You might as well "go big" so that you can have the floor installed in any direction you fancy. Assuming you have calculated the final deflection rating (you need to know the distance between joists "at centre") to achieve the right rigidity, you can run those planks in a circle if you like. And just for fun, make sure you are well equipped to deal with 8" wide planks. Anything over 5" wide require gluing as well as metal fasteners (assuming this is solid wood). And that's where the second layer of subfloor comes in handy. It makes it easier to deal with if that floor ever has to be ripped out (hopefully in 80 - 100 years from now).

Perpendicular from the DOOR. The last photo in your latest post shows the planks sitting perpendicular (running "across" the threshold) is the less attractive way to do this. The OTHER thing to take into consideration is DIRECTION OF NATURAL LIGHT. Assuming your home has the same type of windows/natural lighting, you want to run the planks in the same direction as the source of natural light (windows). That means the long beams of light will be the same direction as the long length of the floor planks. Your last photo shows the OPPOSITE to what I'm pointing out. I would run the long length of the plank from the DOOR to the bottom of the stairs (the opposite to what your last photo shows). Going back to your original plans, that means the LONG LENGTH of the plank will start at the door and run AWAY to the back of the home (past the stairs and into the great room). And all the rooms will keep this direction. It will mean the flow of natural lighting is maintained with the direction of the plank - a double bonus.

Here's one part: "DUCHATEAU Hardwood Floors must be installed according to the National Wood Flooring Association's installation guidelines in order for this warranty to be valid. " From this link: https://duchateau.com/documentation/#install " For cementitious subfloors, the moisture should not exceed 3lbs per ASTM F1869 Calcium Chloride test or 75% rh per ASTM F2170 or a suitable moisture mitigating system be used. " And more: " Duchateau accepts no responsibility nor does it ever warrant issues from either too little or excessive moisture, regardless of source unless specifically in written form." DuChateau refers to the NWFA Guidelines AS WELL AS using an NWFA Certified Wood flooring installer. DuChateau is VERY particular about the adhesives used. You have 3 choices (depending on the place of installation) and those are NOT to be replaced by anything else. I can guarantee it. A 7" wide plank is a MASSIVE width (4" or wider is considered 'wide plank'). They carry heavy price tags. The adhesives are expensive. The NWFA Certified Installation professionals are expensive (for very good reason). All of this is adding up to an EXPENSIVE mistake if a wood floor is glued down below grade. And to be clear, the 'calcium chloride' test requirements (3lbs/1000sf over 24 hours) is a B!TCH to achieve below grade. It is considered 'drier than the Sahara'. It is nigh-on impossible to reach these numbers with a slab below grade. Here is a REALLY IMPORTANT OPTION: " Only Duchateau engineered floors 7.5” wide or less may be floated. " If you have 7" wide planks I HIGHLY recommend you float the floor. I really really do.

Thanks! Mine is Coretec Hayes Oak. This is our Florida hone so we wanted something beachy. Kay, this floor is amazing. Drag whatever you want over it, no problem with scratches from the dog etc. They have many choices depending on the look you want. Noble Oak and Calypso are nice too. This is a winter home for us and our time to renovate was limited. I had heard about Coretec and coincidentally our contractor showed us this floor in a home he just finished. Some boards were left in the box under a bed! Honestly it is hard to choose by just seeing pictures of a product so when my husband and I were both on the same page after seeing it we jumped on it.