Adding 1/2" to 1" height to slab cheaply, then finishing with 1/4" self-leveler

Question

TLDR: I want to level the floor using self-leveling compound, but I need to bring the overall price down. I'm looking for ideas about how to cheaply (and quickly/roughly) raise the low spots to just below level, then finishing with self-leveler.

Details

I am leveling my ground floor in order to install floating vinyl plank. The planks are covering the entire floor, in every room, so I was planning to install it with no transitions.

First I need to level the subfloor, which is a concrete slab. The manufacturer of the plank specifies a flatness tolerance of less than 3/16" change per 10'. I've taken measurements every two feet to see how out of whack the slab is:

(BR closet measurements (right edge) are wrong, it's actually about 1" below grade on average)

As you can see, I need to fix it. As you may have noticed by the legend in the upper righthand corner, I'm using inches.

Making it flat vs making it level

The slab in the living room (bottom) is in okay shape, and it's relatively flat, but not level.

The kitchen (top, middle) and bathroom (down/right from kitchen) are pretty pitted, the result of a recent battle with some very stubborn flooring adhesive, the removal of which involved a rotary hammer. So resurfacing is required. And there are also major low spots that need to be fixed.

There's one part of the plank installation where it will be installed down a short hallway (between kitchen and bath), where I thought I might be able to slope downward and use a second grade for the bath, bedroom, and closet, which are particularly low. But if I still want to follow the 3/16" per 10' guideline and attempt to keep warranty, I wouldn't be able to slope gradually enough to make any real difference.

So considering that I don't have any parts that can remain untouched, I figured I'd do the job right and level the slab instead of flattening it.

Hit a problem

To get a feel for the material, I have poured self-leveler in the bathroom. I really like the result but it took 4 bags of $33 self leveler, which is more than I expected. The bathroom is one of the lowest spots, but there's a lot of floor left to do.

So I want to find a way to lower the cost, while hopefully retaining the surface I get with the leveler.

I have a few ideas:

• Use cheap sand mix to bring the slab to 1/4" below level, then finish with a 1/4" layer of self-leveling compound to get a flat surface (a flatter surface than my concrete skills would be able to achieve with a 100% sand mix solution).
• Add pea gravel aggregate to the self-leveling compound. This is specified by the self-leveling manufacturer as a way to pour self-leveler deeper than 2", but I thought maybe it would work in this case as well.
• [Maybe crazy] Use tapcons or something to securely screw some cheap OSB sheets to the slab in the low spots, then bury the OSB sheets in self-leveler.

Am I on the right track here?

Answer 1

With SVP or LVP the floor needs to be flat, not level. ( even at that the products can be very forgiving if the thickness is 5.5mm or thicker.)

If you don't have an issue with a 1/2 to 1" height difference, ( a lip or drop) to another room, forget that the floor is not level. You need to fill in the dips or big divots. making the floor completely level is an option demanded only by you.

Answer 2

I have done it the 3 ways you suggest. Leveler does get expensive very quickly, and it can easily be more expensive than the actual floor. As others have said, you need to be flat, not level, but how are you going to make something flat and not level? That sounds like too much work. The idea of leveling is that you have a single frame of reference and can use a laser to make sure all rooms are the same.

It really comes down to cost vs. labor. Cement is cheapest but most laborious. Pure leveler (or with gravel) is easiest but most expensive. It all depends on the volume needed. Some quick calculations should allow you to determine the cost of materials. Anything above $1,000 in leveler, I'd just pour cement.