SJ McCarthy, Oana, Thank you both. I did some more research, including calling Kahrs USA and a few local flooring companies. Here is what I learnt - - Kahrs customer service sounded fairly confidence that as long as my total dimension is within the numbers in that installation specification (40feet, 1/2 inch clearance at perimeter) no t-moulding is needed. - Local floor companies also expressed this(no t-moulding) isn't going to be a problem, as much as they are familiar with the business, they are not installation contractors. Then I sketched a my floor plan and drew expansion direction in each room and hallway. I have concluded this is going to be recipe for disaster, unless the expansion rate is really, really small, which i think isn't the case given the required 1/2 gap at the walls : - Assuming each area (rooms, hallway) expansion happens from center and towards walls, I'd have room expansion force, hallway expansion force going against each other at the door, given bedroom is much deeper, likely the stronger expansion force will push the boards in hallway towards the wall opposite of the bedroom, so the movement would be > 3x of the movement if hallway is expanding independently. - I have another room on the other side of the hallway, about 6 feet down, same thing would happen there, only on different side, this would push the hallway into a slight 'S' shape, which would be pretty visible given the hallway is pretty narrow. - Above only count for expansion perpendicular to board direction, the force along the board direction would also be different given hallway is much longer, it might not be a problem if the 'click lock' system allows adjacent board to 'slide' , but if that's not the case, the forces in my case, could rotate the boards at the door for contraction, things would be the same but at opposite direction. combine the seasonal expansion/contraction, my guess would be that in a couple of years I'd either see gaps between boards or the locking loosened. Now I understand why a expansion gap at the door is necessary, basically it absorb opposite movements in different directions. Given we don't want to see the speed bumps on our floor, looks like float-in installation isn't an option for us. Thanks! X.T.

The carpet should not have been cut back so far and the wood should be cut straight across, not jagged like how it's shown in the photo. A simple Z bar would have fixed this issue without having to purchase a wood transition that could break over time due to people stepping on it. And yes, it can break if one side of the transition is on the wood (hard surface) and the other side is on the carpet (soft surface). The soft surface will allow flex in the transition which will cause it to crack and break. A Z Bar is installed under the carpet and allows one end to be tucked leaving a clean finish bumping up to your wood. Photo shows carpet to tile but gives you an idea of the finished layout.

Marble, but it should match the marble in the bathroom and not be something completely different.

Please don't. The warranty will specifically state that the subfloor must be clean flat and smooth. The warranty/installation instructions will clearly state that if you are going over top of an 'old floor' it must be (clean, flat and smooth) well ADHERED to the subfloor. A floating floor is just that...floating. It is not adhered to anything. It should take 30 minutes to remove the old vinyl floor. You will also want to pop off the trim on the walls (probably quarter round or shoe mold) before you install the new floor. Once the old floor is gone and the new floor is installed, you will then reinstall the trim. And don't forget that the new vinyl will TELEGRAPH anything sitting underneath (like bevels from the old floor underneath) as well it will raise the floor height which means you will have to have a NEW transition strip created for the doorway. If you simply rip out the old floor, you will likely be able to reuse the old transition strip currently sitting in the doorway.