I'm sure this topic has been addressed many times but I did not find anything using the search feature, so I will ask again.

I purchased Shaw engineered hardwood from a local Pro Source dealer. I have read the installation manual found on the Shaw installation guide and even called Shaw but I still have a few questions.

Product: White Oak 9/16" 7.5" wide engineered
Substrate: 3/4" new plywood subfloor on ground floor with crawlspace and on second floor. California coastal region--no extreme temperature swings. No vapor barrier due to glue assist.

Questions:
Given the width, this will be a nail with glue assist. Is it recommended to use a trowel on adhesive or a "sausage" application from a glue/caulk gun? I would prefer to use the glue gun type if it is approved. Any particular type or brand recommendations?

What gauge 1.5" minimum fastener is preferred for 9/16"? Are staples or cleats preferred? I have used both 16g and 18g on other installations with similar products. The Shaw installation guide specifies 1.5" minimum staple/cleat but does not specify gauge. I have installed similar products with 18g staples with good results. I would be wary of using larger 15.5g fasteners on a 9/16" plywood base.

Thank you,

Jeff

18 ga. staples are fine. If you are going to be worried about moisture coming from under the floor, then use one of the flooring glues that have moisture protection when full spread. Engineered flooring is more stable than solid flooring, so I think that sausage glue application of two beads at the edges of the flooring and qqlso t butt-joints will be fine. Use at least a quarter inch bead.
Use a poly-urethane floor adhesive from a flooring distributor.

Thanks so much for the information. I now feel comfortable with the 18g staples.

I have installed a few engineered floors with staples but I have zero experience with glue down or glue assist.

For a variety of reasons I assume that the full trowel down application is superior to laying down a bead. I did speak to Shaw and both methods are approved. I have plenty of experience troweling with tile setting but as a novice with hardwood glue, I figured that the bead would be much easier to install but I am willing to trowel down instead. Any thoughts or tips on either method?

The distributer where I purchased the flooring recommended Bostik Green Force ( "Tri-Linking Polymer Technology") or Bona Quantum 851 (silane based). As far as I can tell, neither of these is poly-urethane based. Can you tell me why poly-urethane based is preferred and is there a particular brand that is recommended?



Thanks,

Jeff

Either glue from the distributor will work very well and seal the sub=floor.
You can not go wrong with the moisture cure poly glue, also, just an older technology.