I am looking to convert an old garage into a workspace. The total concrete area is about 20ftx22ft, and has one seam down the center. The pad on the north side of the seam is level. The pad on the south side has a grade from settling after 60+ years. It averages a downward grade at about 1.25 inches over 9 ft. I am going to be putting LVP down eventually, so I need it moderately level, and have been trying to think of a cost effective way to fix the slab.
The first option I thought of was self leveling concrete, but the amount of material that I would need would come out to $1,600+. Which is a lot of money that I don't really want to spend.
The second option I thought of was to put down OSB on one side, and then build tapered joists for the grade side, but I probably would want to put some type of dimpled plastic membrane down? I am not too concerned about water leakage, but it is probably something that most people would recommend.
Another option is to use Dri-Core, but can I shim that much of a grade to level?
Are there other options I could do? What is the best way to level such a large area with that deep of a grade?
Best Answer
If you don't need all the vertical space, two options come to mind.
It would take about 3 yards of concrete to "top" that whole slab with a couple of inches of normal concrete, preferably fiber-reinforced. That won't be in danger of peeling off. However, if your concept of a workspace is LVP floored, the (presumed uninsulated now) concrete slab will be directly coupled to your floor, and that may be unpleasantly cold much of the year, and damp when it's less unpleasant that it's cold. Good if your workspace concept benefitted from a concrete floor, probably bad otherwise, and you seem headed for otherwise.
If raising the floor on sleepers, I would suggest raising the whole floor and insulating under it, rather than laying OSB directly or with moisture barrier (only) on the concrete on the "flat" side. That will give a floor that most people would consider to be more pleasant to live with, and may also reduce your heating bill somewhat, if you are in a climate that involves heating bills.