Who is paying for the flooring installation? If you want it glued you pay him to glue it. The glue will not be inexpensive and the labor will be more money for sure. Did you discuss the installation method with him prior to hiring him? What subfloor prep is he including?

If he doesn’t want to do it get another contractor. IMO when someone does not want to do something it is rarely done well.

Probably doesn't want to glue it down as Patricia alludes to. Keep in mind, if it is glued properly it's going to be a bear to repair or replace.

Wood subfloors are nailed or stapled for the most part.

Concrete subfloors are glued except for floating floors.

That was the vibe we were getting from them! They hinted at it just being more labor intensive (which in turn would cost us more). What WE kept trying to explain to them was that we didn’t care what the cost difference is...we just want the best method. I also felt that they weren’t familiar with that process, which is also why they would just rather nail it. And as Patricia said...we basically would get what we pay for if we had them do something they “don’t want to do”...end of day...we are in the market for a new contractor 🤣

Celadon we have 1 1/2” wood subfloor (had to be built up to meet pre existing floors from adjoining rooms) 3/4” then another piece on top of that)...is glue down common with that as well? Or just slab?

HU, my engineered wood floor was installed with glue assist (a glue snake under every board), and nailed. It feels very solid, no movement with the seasons and fluctuating air moisture.

Nail down over wooden subfloors unless, you have wide planks. Then it can either be glue assist for 5-6 " planks and nail assist for 6" up.

G & S Floor Service they are 6 1/2” ...so sounds like we can’t go wrong either way?

You want to do nail assist. Which is a full spread of adhesive assisted with a few nails.

What's the top layer of your subfloor? Is it OSB or is it real/nice plywood?