[pwd77]

I am leveling an old, cracked concrete basement floor. I need to remove gypsum floor-leveller.

Past work by others includes a variety of concrete and gypsum floor leveler.

Most if it is coming up just with a lot of chipping, but there is a lot of the gypsum that is stubborn to come up. Unfortunately it is hit and miss, making it a very tedious job.

Is there a clever way to speed up the process? One thought is to use dilute muriatic (hydrochloric) acid to dissolve and loosen. Any other ideas?

My strategy is to fill the really low (1") perimeter of the basement with inexpensive sand-based concrete, then finish it all with self-leveling material.

Its an old basement, so it will crack again eventually, but I just want a relatively flat, smooth *cleanable* surface.

Thanks!

[smoothy]

How would you plan on breathing while the muriatic acid was present? That stuff really needs sufficient ventilation. And then flushing it afterwards.

Have you considered renting a breaking hammer (think of it as a small electric jackhammer) with a wide flat bit.

Should handle that work in short order.

[pwd77]

Good suggestion on the breaking hammer

Yes the acid is pretty noxious, but I have good ventilation and a good breathing apparatus. And I have a strong sense of self-preservation.

Any other ideas out there? The really thin gypsum does not come up with chipping, and may inhibit binding of new material

[smoothy]

The breaking hammer should not only chip off the gysum... but should chip into the underlying concrete done correctly leaving a rough surface which would be help binding the new material.

THe ones I mention aren't the small hammer drills ( I should have mentioned this in my last post)... but the much larger ones that are fairly hefty and weight more than 75 pounds.

Home Depots that have rental departments have them among others.

[pwd77]

Update: have an oscillating tool, so took a stab. Result was good:

Poorly-adhered pieces popped right up with the flat scraper
Edge-on the scraper cleaned out cracks readily

Used an old wood/metal blade to take on the better-adhered stuff, which it does fairly well, although hundreds of sf will take a long time. Will hire a helper.

I just learned that concrete over gypsum is a mistake, as they do not bond well. MAPEI site says that sealing the gypsum with a special primer will solve that. Easier than trying to get it all up.

[pwd77]

Ugh, so much for the oscillating tool. Too slow.

Bought a 4" floor scraper, which is doing the job. Very tedious, but liberal soaking of the paper-gypsum makes it doable. Very erratic, sometimes it comes right up, and sometimes its like scraping over teflon.

Note with floor scraper: I had a bench grinder handy so I was able to keep the blade sharp. Very important for me.

Anyway, going to get up what I can, prime it gypsum and all once the paper is up, and put down the topper.