How to prepare my floor to install engineered hardwood?

Question

I currently have linoleum flooring in my kitchen, bathroom and laundry room and carpet everywhere else. I would like to install engineered hardwood flooring throughout my home with the exception of the bathroom and laundry; these areas will likely be tile, but are out of scope for this question.

My home was built in 1956 and has some history, which I'll describe and show with some pictures as background information for my question(s).

• The kitchen's 5/8" thick, plywood floor is lower than the rest of my floor by roughly 3/16" and is roughly 14' x 10.5'.
• The home's old floor was 3/4" solid oak. When the home was renovated before my time, the carpet and a hallway's worth of engineered hardwood was installed on top of the oak floor.
• The oak flooring and plywood subfloor in the kitchen look to rest on top of very thick, tongue and groove boards; probably the original floor of the home. When I inspected the crawlspace beneath these boards, there are no joists (to my surprise). Instead, the boards span large support beams.

Questions

1. Can I install my new engineered hardwood on top of the existing solid oak hardwood?

   • If no, please help me understand why.

   • If yes,

     • What methods are acceptable? Nail, glue, float?

     • What precautions should I take? I plan to check for levelness / flatness and clean the surface of the carpet tacks and any underlayment. Anything else I should do to prepare?

2. Assuming I can do #1 above, then I'd like to raise my kitchen floor to the same level as the oak, so there is no transition. What is the recommended way of raising my kitchen floor 3/16"? My initial research indicates I cannot use self-leveling compound for engineered hardwood because it will crack and generally not be a stable base.

3. Given all of the information here, any tips or pitfalls I should watch out for?

Pictures

Answer 1

After calling around, I found a shop in my area that sells plywood underlayment that is 5mm thick, which is close enough to 3/16" for me to use to raise my kitchen floor.

As for installing engineered hardwood on top of existing solid hardwood, I've been advised it's okay when nailing since the material just needs to be void free and substantial enough to take the nails.

If I were floating or gluing my flooring, but not nailing, I could raise the kitchen area with self-leveling compound, but no idea if that'd be any cheaper, easier to do or overall better. The underlayment plywood I found is $14 for a 4' x 8' sheet, so it's cheap, easy to fix to the floor, and should work well for nailing, floating or gluing flooring on top of. Seems like the plywood wins in all areas.