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Leveling Large Room with Cracked Concrete Floor

3 years ago
last modified: 3 years ago

I believe I am going to need to level a roughly 600 SF room so I can put a durable, water resistant floor on it. The concrete has quite a few cracks, a few of them are fairly large and the vertical offset was up to around 1/2". I ground the peaks down with a diamond grinding cup so the floor looks pretty flat now but I'd guess there's at least a 1/2" difference between the highest and lowest spot, and maybe significantly more. It appears to me that fixing this with self-leveling concrete would cost a fortune.

My thought is that I could use something relatively cheap, like HardieBacker, to fill in the low spots and just use leveling compound to get smaller parts of the floor flat. For example, maybe there's a 15 SF piece of the room where I know the highest point in the area is 1/2" below the highest point in the room. Maybe I just level that 15 SF area and then use a $10 sheet of hardi backer to bring it up to the high point. A 1/2" piece of HardieBacker costs about the same as a 1/4" piece, the doubled volume is basically free. Does anybody see a problem with this?

I just did the math. A 50 lb, $30 bag of self-leveling concrete fills about 0.375 cubic feet. A $10 sheet of 3'x5'x0.5" Hardiebacker fills about 0.625 cubic feet. That makes Hardiebacker about 1/5th the cost per volume.

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