1) Do you guys agree that the floor needs to be glued rather than nailed?

Yes.

2) If so, how would you recommend the installer make this transition from 1/2" engineered hardwood up to 3/4" tile? (ps. Not a fan of the Schluter RENO-U transition strip).

This should have been planned before the tile went down. I know in my house, our concrete slab was poured lower in tile areas than in our engineered wood floor areas. Not sure how they do it if it's not a slab but I would think your GC should have planned for it.

Thanks. We realize that someone dropped the ball, but we have to figure it out now. So any suggestions on how to resolve???

1600 sf on main floor for the 1/2" engineered. I haven't even mentioned we have a similar issue in the basement (concrete subfloor) 1200sf using 1/4" LVP and transitioning up to 1/2" tile due to using Ditra backer rather than cement backer board under tile. Trying to tackle one animal at a time. UGH!!

10 days out from the flooring being installed I would hope it is on site, boxes open and being acclimated. That being said, PPF's advice is certainly worth asking about.

Why not just install a layer 1/4" ply to raise the hardwood floor height - no transition needed.

We had this same problem with wood floor to the tile in the laundry room. My husband found a wood transition strip that matched the wood flooring pretty closely. I really don't even notice that it's there. I'm sure your flooring company could make something that would match perfectly.

...or find a thicker floor while you're considering the spend on the added 1/4".

Well, I am not an expert, but we had a height differential between our engineered wood floor (glue down, on slab) and the limestone tile, which was thicker. I believe that the difference was about 1/4". Our awesome installers ramped up the wood ever so slightly with something (extra glue?) perhaps it was actually a wood subfloor.... (however, I know that they did NOT put a subfloor under the whole square footage of wood floor downstairs--it was something they did near the last foot or so where it meets the tile)

Anyway, it looks perfect. No need for transition strip. I mean, an excellent job. That was a few years ago, and it continues to look perfect.

I did specify in advance that I wanted their best flooring installers, as I wanted no transition strips, and no quarter round. I know it can be done with their expertise.

Edited to add: DH believes they ramped up the slab with some sort of cement-like material.

I recommend the underlayment route. When you need at some point to remove a glued down floor, it is much easier if it is attached to a 1/4 nailed (sometimes stapled) down underlayment. Removing glued floor is a real pain.

We had the same issue. Installed a plywood subfloor under hardwood.

You should at least ask about the same flooring in 3/4".

My suggestion would be 1/4" cork underlayment glued to the wooden subfloor and then the hardwood glued to the cork. This is referred to as a double stick. It works REALLY well for a quick floor height raise. Of course the total cost of the cork + glue = $1.50/sf. Labour costs will be added to that. A 1/4" plywood subfloor won't be much cheaper.

As for the basement floor, there isn't much to be done. The LVP does NOT allow underpad. It is not laminate. A laminate could accept the same 1/4" cork underlay...but LVP will not allow such a thing. The basement transition is probably the place to put the reducer.

If you are trying to get away from a small 1/4" drop, remember that a 1/4" drop isn't much. Regular reducers will deal with this NO PROBLEM. They are $15/linear foot (the wood ones). Each doorway = 3ft. These come in lengths of 8ft or 10ft. For $150 worth of transition strips you can deal with 3 doorways.

If you insist on the flush transition, you are going to be spending $2-$3/sf (includes labour costs AND material costs) do a whole home floor height raise. But that doesn't even begin to tell you how many issues you might create in the kitchen (is the kitchen installed yet?).

And you REALLY need to glue down wood planks that are wider than 5". Even an engineered hardwood will have issues with stability when they are wider than 5". There is no getting around it. You have an installer who has given you the correct advice. That's worth a HUGE amount of heart ache later on.

Being someone who is rather practical on a limited budget, I would go with the reducers any day of the week. Only in situations where there are mobility issues would I consider going the extra mile to get flush transitions. There is something to be said about having money left over in the bank at the end of a build.

1/4 “ sub floor and you are done.