I have a small poured concrete patio, and that I’d like to cover with brick pavers. Can I do this without using mortar?
According to several paver manufacturers, paving blocks can be installed on top of concrete without mortar if you first lay down a 1/2″ to 1” bed of coarse sand. The process is nearly identical to laying a paver patio over ground.
However, this type of installation should be done with caution, since drainage, settling, and cracking can be a problem. Keep these tips in mind when laying pavers over a concrete patio:
Drainage: The biggest problem with laying pavers over a concrete slab is the inability for water to drain through the blocks and down into the earth. Before you begin, make sure your concrete is properly sloped and doesn’t puddle. Keep this drainage slope in mind when adding your pavers, and make sure the edge that drains water stays low and permeable. You can also drill small drainage holes through the concrete every few inches, to help any puddling water seep into the ground.
Sand in Joints: When you’re finished laying the blocks, firm them up by filling the joints with polymeric sand. While sand joints are still permeable, if properly set they can help excess water run off the surface rather than puddling.
Edging: Like any other type of installation, a concrete slab paver patio needs to be firmly edged, to keep the sand and pavers from settling and squishing around. However, your edging needs to allow for water to drain; if it’s watertight, your patio could turn into a bowl of water when it rains.
Semi-Mortared: Rather than dealing with edging, some builders use mortar or adhesive to hold the perimeter course of pavers in place. To do this, you’ll need a clean perimeter around the sand bed, so the blocks can stick directly to the concrete. Make sure the mortar and sand bed are the same thickness, so the blocks will be level. This method can create a nonpermeable edge that could cause water to puddle under the pavers.
Height: Your new patio will be up to 3” higher than the original concrete slab. Be sure to plan for transitions to other areas, especially if the patio adjoins your house. Most building codes specify how far a masonry patio should be from a home’s siding, and you may need to install flashing to keep water away from the house.
Concrete Condition: If the concrete slab is broken or in terrible shape, you might be better off ripping it up and starting over.
Not for Driveways: In general, this isn’t a good method for driveways. The underlying concrete doesn’t allow for the pavers to give, so they’re more likely to rock and crack.
Patio Extension: You can also extend the size of your patio, by digging out the soil around it and installing a proper gravel and sand bed, then screeding and tamping the sand across both the old and new areas to make it level. However, keep in mind that the non-concreted areas will be more likely to settle, and over time your patio may become uneven.
Don’t Rule Out Mortar: If you’re new to this project, don’t be intimidated by the prospects of mortaring a permanent paver patio. In my opinion, mortar would be less work!