You've decided to build a new fence and you know just where it should go. The only problem is, there's a stretch of concrete you'll have to cross. Installing fence posts on concrete is not as difficult as it first seems. You will need a galvanised fence bracket and four Tapcon-style concrete screws for each post that will be installed on top of the concrete.
Use a mason's line and wood stakes to lay out the line of your fence. Drive one stake in at each corner and stretch the line taut between them. Measure from the first stake to determine where you will place your posts. They are typically set at each end of a fence panel, with two panels joining in the centre of each post.
Mark the mason's line in the position of each post with a piece of tape. Mark the actual post position by using a plumb bob or bolt tied to a string. Dangle your plumb bob or bolt from the tape mark on the mason's line to a point just above the ground. Use chalk-line chalk to mark the ground or concrete in each location.
Dig post holes in dirt one-quarter as deep as your desired post height. Set your posts in the holes and fill with concrete to 2 inches below ground level. Use the level to ensure the post is straight, and allow the concrete to dry before filling the remainder of the hole with dirt.
At the post locations on the concrete, use a post bracket as a template to mark the holes for the concrete screws. Make sure the bracket is sitting square to the fence line and is spaced accurately from the last post---typically 8 feet from the centre of one post to the centre of the next.
Use a 3/16-inch masonry bit to drill pilot holes in every location marked for each bracket---most have four, and use them all. Drill each hole 2-3/4 inches deep. Blow the dust from the holes. Place the bracket so that the holes line up and use a No. 1 Phillips bit in the drill to drive 1/4-inch diameter, 2-1/2-inch concrete screws into each hole. Repeat for each bracket needed.
Cut your posts to length. Posts on dirt can be cut after the concrete dries. Measure the desired height and mark all four sides with a square. Cut the posts using a circular saw. Posts on concrete are best cut before installing. Set one post in each bracket on your concrete. Attach them using 2-inch treated deck screws. Drive one screw into each available hole for best results.
Set your fence panels in place and attach them to the posts using 3-inch treated deck screws. Use at least two screws for each end of every horizontal rail. Use a scrap fence picket or other three-quarter inch material as a spacer under the panels above the concrete to avoid moisture damage.
Things you need
- 4-by-4 inch treated posts
- Fence panels, any style
- galvanised 4-by-4 fence bracket
- 2-1/2 inch Tapcon-style concrete screws
- Treated deck screws