How to Pour a Concrete Curb Over Existing Patio
- 1). Lay down two 1/2 inch wide strips of epoxy sealant the full length of your patio edge where you'll be placing the curb, to help the new material adhere to the existing patio surface. The strips should fall one inch from the edges beneath your laid curb.
- 2). Mix the concrete curb mix. The curb mix should be a 0-slump concrete mix, which will end up dryer and thicker than the concrete normally placed into rubber or wooden forms. The actual shape of the concrete curb is created by the extruder; the curb will come out of the machine already free-standing.
- 3). Choose the mold shape for the curb that you'll use and attach it to the machine. Place the curbing machine, which you can rent at a local equipment rental shop, at the point you wish to begin creating your curb. Start the engine and run it for several minutes allowing the engine to warm up.
- 4). Place a shovel full of concrete into the curbing machine hopper. The curbing machine will extrude a line of curb as you pull it backwards. When the hopper empties, place another shovel of concrete into the machine, repeating the process as you drag along the machine, pouring without breaks.
- 5). Stop the curbing machine when the curb has been completed. Raise the front of the machine and remove it from the extruded curb.
- 6). Place a small bit of curbing material onto the end of the curb and finish it by hand, using a margin trowel to shape it. If the curb ends at the edge of another surface, such as a sidewalk, add a beveled edge to the curve, creating a slope leading to the second surface edge so as not to create a tripping hazard.
- 7). Finish the face of the curve with the front trowel, using a two to three foot piece of plastic the same height of your curb, at the rear of the curb for support. The trowel should be dragged along the length of the curb smoothing the edge. The front trowel is made specifically for the curb mold shape used and will match that extruded shape. Use the back trowel to finish the back of the curb. The back trowel is also specific to the curb design.
- 8). Place an expansion joint every three feet along the curve using a putty knife, and remove any excess concrete from the surface of the patio and lawn. Allow the curb to cure before using.
Source...