You can get a reduced echoey sound with something like Floor Muffler, but no, it will never sound quiet like a glue down floor.

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.

It is highly dependent on the AGE of your slab. If it is older than mid-1980's build, then you have a HIGH chance that you do not have a vapour barrier underneath. That means your glue costs just when up. You have to move to the big boys of glue = $2-$3/sf just for the material. The labour costs will keep going up. A floating floor can be stabilized by leveling the subfloor and using something like 6mm cork underlay to help with the 'solid' feeling under foot. A properly installed floating hardwood floor with cork underlay should feel as solid as a glue down floor. I've seen it time and time again. Start with the age of the slab and then make your decision from there.

Please do NOT install over hardwood. I don't care if it is glued down over concrete or nailed to plywood. Vinyl and wood FINISHES do NOT work together. In fact the chemical transfer (and this is the LEAST of your worries!!! ahem!) from the wood finish to the vinyl is almost 100% guaranteed. That chemical transfer = heavy staining of the vinyl. And heavy damage to the wood floors underneath. Which renders BOTH floors unusable. And if the new owner finds out about the damage to BOTH inside of a year (or two...depends on your State's liability laws) you will STILL be on the hook for the damage/removal/replacement. The BIGGEST issue is NOT the staining - when dealing with glue-down hardwood over concrete. The BIGGEST issue is moisture damage and mold/mildew contamination. Concrete breathes and gives off moisture. The adhesive used to glue the wood is a moisture barrier but it never really 'cures'. It stays flexible. When you put vinyl over the wood you CAP the moisture. You TRAP it. That bit of moisture in the GLUE then soaks into the wood...that wood stays soaked and NOW you have huge amounts of mold growth. The chemical staining of the vinyl then SPEEDS UP. Instead of taking 5 years to stain the vinyl (over plywood subfloor) the soaked wood causes the chemical staining to occur in 1-3 years. That's when you pull up your vinyl to find the soaking, molding, useless mess. Now you have to do it all over again but this time with MOLD REMEDIATION costs added in! It's your call. But the installation instructions clearly state not to do it. They don't do this to p!ss off customers or to cost the homeowner more money. They do this to PREVENT irritation and to PREVENT greater costs later on. You wanted vinyl. You currently have hardwood. You will need to pay the piper to get this done properly. Of course if you used laminate you wouldn't have this issue. You could have run the laminate right over top of the hardwood without issue....just sayin'.