How To Level A Floor With Cement Board. If it’s a hump, then write that on the floor and the same goes for a dip. Then, go over any particularly high spots with a concrete grinder so they're level with the rest of the floor.
Pour it into the hole or snaking crack, and smooth it out with a putty knife so that it is level with the rest of the floor. Mix grout according to manufacturer instructions, and apply to spaces between the tiles, starting at the corner and working at a 45 degree angle. Nail or screw to secure them to joists.
Leave a 1/4″ gap between the backer board and walls and 1/16” gap between the sheets of backer board.
Precut and fit all the cement board and then lift all of the cement boards out. Cement board screws spaced every 4 in. Notched trowel and use the notched edge to “comb” the mortar. Jim spread a small portion of mortar over the floor using a small notched (1/8″) trowel.