Raising Enclosed Lanai Floor
 

My lanai is enclosed with sliders that sit higher than the floor but I hate the step down of 3.5” from the home to the lanai
Presently there is a tile floor I would go right over if I raise.

Question :: What options are there for raising floor to house level?

Polymer-modified concrete is an option but can a
wood frame with a sub-flooring board frame that are be built over existing tile floor with a Vapor Barrier?
I would like to use LVT Planking after the raise.

I asked the exact same question to Sumter County building department about a week ago, and was told this was not a good idea due to the possibility of termites. I was going to use pressure treated lumber, and they stated these release "vapors" that may be harmful, I have not had a chance to check out this claim. I was NOT told this would NOT be accepted, very strange. Bottom line, I did a basement up north, and the requirements were, vapor barrier between the concrete and the studs.
I am going to be following this post, as I would be able to do the wood based floor myself, versus the poured concrete (about 5.5 cubic yards) and associated labor and the leadtime.

If all pressure treated wood is used in the construction for framing and plywood then in reality there shouldn't be a safety issue. CCA (copper chrome arsenic) pressure treated wood has been found to give off minor "fumes" if damaged or breaks down but it seems in reality it's very likely no more worse for your health than operating a gas stove or grill. As for termites, I don't believe there's much of a chance that termites will damage CCA treated wood.

I have plans to put down LVP flooring in my lanai and would like to raise my height up as well. I'm wondering if steel studs and cement board might be an acceptable alternative.

I like your idea. Following

An option you may consider is a product by NewTech Wood, search for NewTechWood.
 

Not a finished floor replacement as you have described but may offer a cost effective option all things considered. Looking at his myself for my lanai and thought it was worth sharing.