Thank you- is there a way to still make the slab from concrete? Is there perhaps a technique or a barrier we can use that’s considered adequate to protect the drywall from the concrete?

I wonder if flashing would prevent contact?

How big is the step down? I would think cut away the drywall and wrap the room with pt 2x whatever the correct height but I’m sure there are other ways

You could either remove the lower portion of drywall and replace it with pressure treated plywood or use a waterproof membrane to protect it. 10mil poly sheeting provides a good, cheap barrier and could be stapled to the drywall and even sealed at the bottom with waterproof caulk. After the caulk set up the excess poly sheet on the floor could be cut off before pouring concrete.

Thank you all for these ideas - will research them. Sincerely appreciate it.

Hard to believe that's a real licensed architect.

We use strips of XPS under basement framing to keep the wood or steel away from the concrete.

Are you sure you can't move? I would not convert a garage into a room. I am in the process of viewing homes to downsize and not having a garage or at the very least a carport is a deal breaker for me, and I imagine many other buyers.

Pressure treated wood should not come in contact with concrete.

Perhaps remove the drywall and install a 2x untreated wood member against the stud wall where the top of it will be the top of the concrete.

Thanks everyone-points all well taken - sincerely appreciate it.

Well where ilive garages cannot be converted to living space without a whole new foundation as for drywall touching concrete not a good plan . I for sure would not use pressure treated wood inside a living space Not sure where you are so can't comment on the skills of the "architect"

Thanks everyone we live in Miami - I will look for another architect to get another opinion (or two)

Do you have a 10mm vapor barrier under the garage concrete now? If not, this is a good opportunity to put one down before your pour. You can also put foam board down to insulate.

Too many unknowns.

Are you currently havng a problem with moisture at the base of the exterior garage walls? Are the exterior walls wood or masonry? Are the floors of your house wood framed or on a slab?

Photograph how the exterior wall rests on the slab/foundation. You might need to photgraph it at the jamb of the garage door showing the inside and outside.

Has the designer shown you any details?

Show us sketches of the existing conditions.

"Pressure treated wood should not come in contact with concrete."

Say what??