So I may have a couple to many beers when pouring the slab for my new outdoor fireplace, and "forgot" that I needed to pour it level and not follow the slop of the patio. Whoops...



I bought a concrete grinding disc for my grinder and am about to set out on a marathon of correcting my mistake, but before I inhale clouds of concrete dust, I figured I'd ask the brain trust if they had any other ideas of how to level this without spending hours grinding my mistake away. FWIW, this isn't under the main fireplace, its on one of the wings which will be the firewood holder box area and will have two courses of CMUs to build it up to box height. The motor I'm using is rated to 1/2" height so I only have about 2 1/2-3" to make up :-(

  • Is that the difference from lowest to highest, 2 1/2-3"? – Jack May 9 '20 at 4:06

Starting at the highest corner or spot, and level from there.

It can be done a few ways, first you could set the first 2" block far enough from the high side so that it is level with a thin setting bed under it, and fill the rest of the area that is too thin, with masonry cement.

Or you could set the 2" block at the highest side, using enough mud to run it level, until there is enough drop to add 4" block to keep it level.

Another way is to figure out the amount needed to cut off of each block, so a relatively uniform level/layer of mud is under each block. This way may look the best if there is no other surface to be applied to the block to hide the build up.

  • Thanks, I'll give the first method a try. It will get a stone veneer after, so it doesn't have to be pretty, just structurally sound. – Chris May 9 '20 at 15:23
  • To help control the mud going down in the thin spot, use 2X4s to retain the mud until it sets up. To remove the 2X, tap with a hammer on the butt end to slide the 2X along the face of the mud to break the seal made by the wet mud – Jack May 9 '20 at 17:43

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