This story show you how to prepare a concrete slab for flooring by making sure that it is solid, smooth, and level.
No matter what kind of finished flooring you plan to install, the substrate must be properly prepared. In the case of a concrete slab, it should be solid, smooth, and level. Inspect its condition before you build new framing (if needed) and install any flooring materials. First look for large cracks and sagging sections. If they're present the base is not adequate. You'll need to remove sagging sections and pour new concrete.
Cover isolated, inactive cracks with an isolation membrane. Completely cover new concrete and any other floors you suspect might develop cracks. Fix active cracks -- those that are growing longer or wider -- instead of covering them up. Active cracks can indicate serious structural problems and can pull the floor apart.
Repair surface: 4-foot level, sledgehammer, cold chisel, carpenter's pencil, margin and mason's trowels, grinder, masonry-grit abrasive wheel, vacuum, brush, mop Repair structural defect: sledgehammer, crowbar, wheelbarrow Install membrane: roller, mason?s trowel
Using a level, troweling, grinding with a power grinder
Remove finished flooring
Repair surface: hydraulic cement or thinset, muriatic acid, rubber gloves Repair structural defect: gravel, reinforcing wire, concrete mix, 2x4 screed Install membrane: membrane, adhesive
Divide the slab into imaginary 6-foot sections and check each section with a 4-foot level. Mark cracks, high spots, and other defects with a carpenter's pencil. Cracks may be a sign of a structural defect that will require a professional to correct. Others may be D-I-Y repairable.