Installing paving stones over existing concrete and cement slabs can be done in as little as one afternoon. This upgrade makes the overall appearance of a patio and surrounding landscape much more appealing because paving stones have a more finished look than bare cement. This project works best when the cement slab is smooth and level without any cracks to make the surface uneven. Uneven or unleveled cement may cause the paving stones to crack over time.
Clean the cement slab with a pressure washer and dish detergent, or use muriatic acid if the cement is very old or weathered. Scrub the cement with a deck brush and rinse thoroughly.
Mix the dry mortar with water to achieve a consistency like peanut butter.
Spread the mortar over the cement slab with a trowel to a thickness of 3/4 to 1 inch. Spread the mortar so that it is close to level.
Lay the paving stones directly onto the wet mortar in the desired pattern. Work with only small sections at a time and measure as you go to ensure that the stones are level. Let the mortar and stones cure for 48 hours to ensure a sturdy base and firm hold.
Pour polymeric sand onto the stones and sweep into the cracks with a broom; you may need to tamp the sand down to ensure the cracks are completely filled. Polymeric sand help bind the stones together and often has an organic binder or cement mix that hardens after it gets wet.
Anchor landscaping timbers around the newly paved slab with rebar to prevent the stones from shifting over time. You can use lumber for the frame instead, but landscaping timbers tend to blend better with natural landscapes.
Lay the stones out before starting, particularly if you want to create an intricate design. This will ensure that you have enough stones and give you an idea of the best placement before they are set in the mortar.