April 2015 Job of the Month:
When it comes to home renovations, some neighbors can be competitive. The owners of this house lived in a retirement community. Everyone in the community seemed to want their homes to look good. Renovations were popular. Decorative concrete can be a great way of improving the appearance of a house, so the homeowners contracted us to lay down a scored concrete patio and sidewalk in the front of the house and a scored concrete patio in the back.
In stamped concrete projects like this one, we lay down a thick concrete overlay on top of the existing concrete layer. At first, the new layer is smooth and lacks texture, but while the layer is still wet, we then add textures and patterns that imitate the appearance of stone. These effects can be created through one of two methods. For the first method, we would use prefabricated mats to stamp both a stone-like texture and the edges of stone tiles into the wet concrete. In the second method, we use a pre-fabricated mat to stamp a stone-like texture into the wet concrete, wait for the concrete to harden and then use special tools to score the edges of tiles into the concrete. We prefer the second method, since it gives us greater control, especially when we run into unexpected problems.
At this house, the second method turned out to be the better option, especially for the scored concrete patio in the back of the house. The first part of the project went smoothly; we laid down a scored concrete patio and a scored concrete sidewalk in the front of the house without any trouble. We laid down the overlay material, and while it was wet, we applied a texture that imitated ashlar slate. After the new concrete layer had dried, we used blue chalklines to create guidelines on the hardened concrete, and then we scored edges of tiles into the concrete. The tile edges were parallel with the edges of the patio and the sidewalk.
Next, we moved to the back patio. After cleaning the existing concrete and laying down the overlay material, we stamped the ashlar slate texture into the wet concrete overlay. We let the concrete dry, and then we returned to the home to finish the project. The plan was to create the appearance of ashlar tiles that were parallel to the edges of the patio. Before scoring, we used blue chalklines to mark the places where the tiles would be scored. It was at this point that we ran into a problem.
The contractors who'd laid down the original concrete layer had also scored control joints into the layer. The back patio was a big slab of concrete, about ten feet wide and 20 feet long. The concrete layer also sat directly on the ground. Whenever the ground becomes wet, cold, hot or dry from drought, the ground can expand or contract. This causes movement and can lead to cracks forming in the concrete. These cracks will form at the concrete's weakest point, but a control joint can help to control where the cracks appear. The joints are typically ¼ of the depth of the concrete layer. The concrete within the scored cut will be weaker than the concrete around it. The idea is that, with any luck, the concrete will crack within the joint and not anywhere else. Control joints can be pleasing in appearance. If the cracks form only in the joints, the joints can also help to maintain the overall appearance of the concrete layer. The overlay material we used in this scored concrete patio project did not cover up the control joints. At first, as we worked on this project, the control joints had appeared to be straight and parallel with the edges of the patio. The blue chalklines should have been parallel to both the edges of the patio and the control joints, but instead, the control joints were off-center with our chalklines. It didn't look good.
We spoke to the homeowners, and we decided to shift the angle of the tile edges. We washed off the old chalklines and laid down new blue chalklines that were diagonal to the edges of the patio. We then scored diagonal tiles into the patio. The result was a scored concrete patio with diagonally placed ashlar-like tiles. The result wasn't what we'd wanted originally, but it looked great and they were very happy.