Installing a fence over asphalt may require anchoring a post in the surface. Once the post is installed, the fencing is attached to the post in the same manner as any other area of fencing. Rent a small jackhammer or use a hammer drill with a cold chisel bit to make this job a lot easier.
Mark the location for the fence post on the asphalt with chalk.
Cut through the asphalt with a small jackhammer or hammer drill at the location marked with chalk for the post. Widen the hole from centre and create a hole in the asphalt 2 to 2½ feet in diameter.
Remove the asphalt pieces from the hole. Dig the hole 2 feet deep, using a post hole digger.
Undercut the asphalt, using the cold chisel and lump hammer. Create the opening on an angle that slopes from the edge of the asphalt to behind the edge of the top of the asphalt all the way around the hole. Remove all debris.
Set the fence post into the hole and measure the amount of fence post above the ground. Replace or remove soil so the amount of fence post above the surface of the asphalt is consistent with the other posts.
Mix the concrete in a large bucket according to the directions on the package. Use a trowel to mix the concrete until it there are no dry spots. Scrape the edges and bottom of the bucket to be sure to mix all the concrete thoroughly.
Place newspaper around the hole so spilt concrete mix does not get on the asphalt. Pour the concrete into the hole around the fence post until it is approximately 2 to 4 inches from the top of the hole.
Place a level on the side of the post and check the bubble to make sure the post is plumb. Check for plumb all the way around the post and adjust the post as needed. Hold the post in position until the concrete is firm enough to hold the post securely. Allow the concrete to set up for an hour or more before patching the remainder of the hole with asphalt cold patch.
Press asphalt cold patch into the remaining 2 to 4 inches around the fence post with a trowel. Use a piece of 2-by-4 to rub the top of the cold patch and feather it into the existing asphalt around the hole.
Attach the fencing to the fence post in the same manner as any other location.
Clean concrete tools with water before the concrete can dry on them so they can be reused.
Never use a regular hammer with a metal head to strike a cold chisel. The head of the hammer can shatter. Wear safety glasses or goggles when using cold chisel, jackhammer or hammer drill.