Greetings all, first off a big thank you to all the people that responded to my fireplace demo thread. I have removed the hearth and scraped up all the loose mortar and such. I'm having the chimney cleaned and buttoned up and after that (and cleaning/up reworking the sexy temporary attic blocking pieces of wood) it's on to building the new wall. So I now basically have this concrete "slab" in front of the fireplace that is a tad *lower* than the plywood subfloor that would have butted up against it when it was in place (see attachment #1). My goal is to now construct a partition wall about 16-18" out from the original wall. I will frame this out so that we can do built-ins and a middle section for a bioethanol burner channel and a TV above it.
So, the existing concrete runs the entire length of the wall and is, of course, not level. So I was wondering if my best bet would be to use some form of "self-leveling" mix to bring this concrete slab thing to a level height, so that I could then attach the sole plate to it? I've never worked with that stuff before but I'm going to need some kind of level surface here correct? If it's a go that I should be leveling the surface with some self-leveling mix, do I bring it right up to the plywood subfloor? Or stop it 3/4" or 1" before it? Once the the leveling compound has cured/setup is it just like going into concrete/masonry at that point? I would use tapcons to attach the sole plate to the leveler-concrete underneath?
Also, on an install like this, what do you all recommend for the best way to make this wall "straight"? Just measure the sole plate a set amount of inches from the existing wall (the wall the heart was built-out from)? Use something like the 3-4-5 rule to the outer wall? Measure the top plate out a set amount of inches from the existing ceiling edge to make its line?