I have a room that someone added over what was previously an outdoor concrete patio. I would like to put down a wood floor laminate or similar floor over the concrete. Unfortunately, the concrete slab has split in some areas and is now not level enough to do this without leveling the floor somehow first. I'd rather not use any carpet in this room because I'll have washer/dryer/water heater in there and it is large enough to act as an extra bedroom or office as well.

What would be your suggestions for going over the existing concrete so that I can best have a fresh, flat surface to work with?

Should I try pouring concrete over existing surface (not sure this would work well) or build it up with 2x4's then plywood? Or something else altogether???

How about mudjacking the slab?

Self leveling floor lever is made for this very application. It is a powder that you mix to the consistency of a malt and pour it out.

before you can make an informed decision you need to figure out why the floor cracked. You also need to determine if there are any settlement issues with the exterior wall of this room

Presuming that the are no longer any further settling issues you have several choices including;

1. Fill the cracks & seal the concrete to help prevent moisture from coming up thru it. Install either a wood floor that comes attached to plywood or a vinyl floor like the LifeProof vinyl floor from HD

2. Fill the cracks & top the entire area with light weight gypcrete then proceed with flooring as suggested in #1

3. Fill the cracks, seal the concrete and 2x sleepers scribed to the existing slab then add a layer of 3/4" Advantec followed by finished flooring

Thanks for the suggestions. I, too, forgot about a concrete floor leveler. This may work.

The cracks are up to maybe 3/4" wide at the widest points and the height difference is maybe a 1/2" give or take.

This home is about 75 or 80 years old so the settling could have happened anywhere in that time I suppose. And we did have a pretty good quake in the mid 90's so that could have exacerbated or started it.

I'm not familiar with mud jacking. I guess I'll have to look into that...

Floor leveling compound will be your cheapest way out.

But I think wood frame with plywood subfloor is the BEST way out. It will stay level if/when the concrete continues to shift. And you said you could raise it 6 inches anyways...

I would seal the cracks, even with backer rod or foam. Just to keep the moisture from coming up. Lay at least 6 mil plastic, overlap and tape the seams to put in a good moisture barrier. Lay 2x sleepers, shimmed to level, insulate with good foam board between them, top with plywood to make an insulated, raised, level floor. Then you can use whatever flooring you want on top of that.

I have an enclosed patio with a stone floor that my tenant didn't alert me that tree roots were lifting the floor. And each time i inspected the home, annually, they had a desk or bed covering this damage. They never told me.