How should I flatten (not level) a concrete subfloor?

Question

In the final stages of finishing a room in our walk-out basement. This particular room has a long history, as it was originally a garage. Thus, it has a slight pitch from the back of the room towards the wall that once contained the garage door (which is now a sliding glass door).

Unfortunately, there is a ridge down the center of the room where the concrete bows up about 3/8" of an inch over a 2' wide strip. I believe that this kind of ridge will cause issues when laying the laminate flooring.

My initial thought was to use self-leveling compound. However, being self-leveling, it will run down and pool quite thick at the front of the room, and require a significant amount to do (and might even go higher than the threshold of the sliding glass door).

I am unsure as to what type of product I could use that would be trawl on, and thick enough not to run, yet bond well with the underlying slab. Any thoughts on the best way to flatten a concrete floor that has a pitch in one direction that must be maintained?

Answer 1

Cut slots in the concrete close together with an angle grinder and diamond blade, knock off the little ridges you have just created, and then either flatten with a cup grinder or level up with compound.

Answer 2

I would look into renting a bull float and pulling one of the resurfacing cement products that have plasticizers in them. They can be troweled to knife edge thinness. If the floor has been sealed (does a drop of water bead up or absorb?), you may have to abrade the sealing off, to allow the new cement to bind. Latex admixtures are usually used to promote binding.

If you get 3 to 4 ft float, you can pull a wide ramp to lessen the hump. You may want to buff the transition area with a rubbing block afterwards.

Once you make both sides of the hump tapered, the laminate will be able to transition, especially if the long dimension of the laminate is parallel to the ridge.