Hi guys. I bought 3/8" -5" wide engineered hickory from Bruce hardwood floors. I have 2 different conditions in my house: (A)concrete slab, and (B) wood sub floor with crawlspace below.
Crawlspace condition:
The crawlspace has wood joists and 1x8 planks (at 45 degrees) on top of them. We removed the old wood floor so now we need to install the new one. We are going to have a company come in and spray 2lb high density foam to the underside of the floor and joists. This will create a moisture barrier. I called Bruce and they said if we do that we could basically install the floor 1 of 3 ways:
1. float on their "quiet comfort" underlayment and use a bead of everseal adhesive to glue sides of boards.
2. Glue down. We would probably need to add plywood first for this as the existing 1x8's have gaps between them.
3. Staple the new floor directly to the existing 1x8's

The guy from Bruce said that people prefer glue down or staple down so we are leaning towards the staple down. We are going to screw down any of the 1x8's that are loose but i am worried that they may not be level in some areas.

If they are not level how would I fix that before we staple the new floor?
Do you guys agree with the staple installation method?

Concrete floor condition:
For the area of the house with the concrete we will probably glue or float.
Any recommendations on which is best? If we do glue down is it a pain to replace the floor in the future?

thanks

Personally I would do 3/4 plywood over top the 1x8 just because they are dimensional lumber which is not always flat and your using a prefinished engineered and not a sand n finish solid. Not sure why Bruce didn't mention that.

Gluedown on concrete is always harder to remove and then theres many hoops to jump through.

Be sure to check for flatness in the existing floor. Use an electric hand planer after you recess screws or the existing nails. Read the instructions to find the requirements for sub-floor flatness. Your warrantee depends on it.
You can grind a slab with a diamond disc on a heavy duty body grinder.