I am double posting this (from Design Dilemma) because I hope for professional flooring advice and also suggestions from people who've done this. We live in the Pacific Northwest (rainy winters and dry summers). Our house is 13 years old with ¾” OSB subfloors on joists 16” on center. We want to remove the carpeting in the dining room, living room and hallway (above grade) and downstairs hallway (on grade), and replace the carpeting with wood flooring. We also want to keep the height difference between these rooms and the adjoining tiled kitchen to a minimum. Because of this requirement, I am leaning towards 1/2" engineered wood rather than solid 3/4" wood. The new flooring would be professionally installed. Am I correct to say that OSB does not hold nails/staples as well as plywood for nail-down installation, nor does it provide a suitable surface for glue-down engineered wood flooring installation? Would glue-down installation avoid the squeeky-squeeks that might result from a nail-down installation? We have heard that installers recommend having an underlayment put down over the OSB to provide a better adhesive surface for engineered wood flooring and we would have that done. I don't think a floating floor would be an option because of the upstairs room size (50' x 15') and high ceilings (possibly too noisy). For glue-down engineered wood flooring, what underlayment would be best between the OSB subfloor and the engineered wood floor? How thick would it need to be? Thank you Mary

The acclimation you've been recommended to use is generally how we've done floors forever EXCEPT when using wider planks. As was noted above, have the plywood and wood checked. If they're too far apart the area can be dehumidified to bring the plywood moisture down and/or the wood will add moisture if it's particularly dry. Make sure the contractor is putting a vapor/moisture barrier (not retarder) between the concrete and the plywood. I don't recommend any barrier between the wood and plywood. Some pros have been burned using (probably cheap) water based finishes and refuse to use anything other than oil based. Others think you should use only the newest technology finishes and exclusively use water based. We use both. With a stained, hand-scraped White Oak, I would choose oil based polyurethane. No water based finish compares to the durability of oil modified. Considering the cost, it's a no-brainer unless you have special circumstances. As to staples vs. nails, we've used both and seen little difference in the performance. My preference would be for nails but the industry seems to have moved more toward staples.

And just to be helpful (probably not...but here we go), a 5" wide hardwood needs "glue assist" with a nail in place install. So there must be some gluing going on. The extra cost of the sound reducing membrane isn't what is driving the cost up. It is the two layers of glue (yes the acoustic underlay must be glued and then the hardwood glued over top = double stick) and the extra labor to do everything "twice". Twice the labour, twice the glue = twice the budget. A glue down hardwood is the most expensive form of hardwood install we have. Nailing is the cheapest. A floating method is between the two. A glue assist for a wide plank (ahem...5" ranks as wide plank = needs glue assist) is more expensive than a float...but not as expensive as a full spread glue down install. Check to ensure the quote for the nail down includes the glue assist. If it doesn't, then they could be missing a step. The 1/4" cork underlay (from iCork Floor) = $0.66/sf. Some shipping costs (maybe $0.45/sf) brings it to about $1.10/sf for the cork. The other $5/sf is the glue (assume $1/sf per layer = $2/sf) and the extra labor to do all this gluing. The material only adds $3/sf. The labor is the other $3/sf. $3+$3 = $6/sf for this install. If you MUST HAVE acoustic insulation + solid hardwood, then you must have the extra $6/sf. There is a possible solution: floating hardwood. Yep. Float the hardwood (very few solid hardwoods are allowed to float...so you need to look at engineered for this) and you FLOAT the cork underlay. No glue = reduce the material costs by $2/sf. Since floating a hardwood is just SLIGHTLY cheaper than a "nail + glue assist" install, the cost of labor for the floor itself won't change. Switch to an engineered hardwood that can float and then add the 6mm cork underlay. It will add $1 - $2/sf to your current quote. My calculations indicate you have 2500sf of flooring. The cork underlay will only add $2500 to your material costs. Compare that to $15K for the double stick total. The solution = floating engineered hardwood. You can have your cake and eat it to.

Before you glue to the concrete, I would like to know a few things: 1. Is the slab on, above or at grade (on the ground, above the ground or below the ground)? 2. How old is the house/slab? Old homes have issues with moisture (moisture barriers were not consistently used until the late 1980's - mid 1990's (depending on where you live). As someone who is overly cautious with hardwoods and concrete slabs, I like to be QUADRUPLE sure that a glue down is an option. And even then I would consider floating if I am not 100% sure of moisture readings. As an aside, I've read the technical specifications of this floor. I would say they are underwhelming at best. This is a 9.5mm engineered hardwood with 1.2mm wear layer. It is 5" wide (which could indicate 'glue assist' would be a good idea). This floor consists of short lengths. The longest plank will be LESS THAN 48" (states 47" as the longest plank) with an average plank length of 29.5" (less than 3ft). At $2.25/sf, it will cost more to install the product than the product is worth. I hope your installer is aware of all these shorts. Shorts make for a LONG install. And the longer it takes to install the product, the higher the price you pay the installer. I wish you luck. I really hope the 1.2mm wear layer stays attached to the 9.5mm thick plank. To do that, you will need EXCEPTIONAL humidity control. As in you need a super-duper high-end HVAC system that can have humidity added/removed with the touch of a button.