How to Build a 2×4 Deck Rail on a Concrete Patio: Drill 1/2 inch holes in the concrete patio, install concrete wedge anchors, 4×4 post standoffs and mount the posts. This project is continued from How to Build a 2×4 Deck Rail on a Concrete Patio – Part 1.
Install 4×4 Post Concrete Anchors
The centers of the posts are marked with a + on the concrete as shown near the drill bit. In my case the deck rail is 43″ long. A 4×4 post is actually 3.5 inches x 3.5 inches. To find the distance between the post centers I subtract 1/2 width of each post, or 1-3/4 inches:
43 inches total width minus 1-3/4 inches (left post) minus 1-3/4 inches (right post) = 39-1/2 inches distance between the post centers.
To mark the post centers:
- Locate the right post and mark the center as shown below.
- Measure 39-1/2 inches to the left and mark the center of the other post.
- Drill 1/2 inch holes with a hammer drill for the concrete wedge anchors.
I used Red Head 1/2 inch x 5-1/2 inch threaded concrete anchors purchased at the home improvement store:
Concrete wedge anchors have a metal sleeve on the tapered bottom end that grabs tight when the anchor is pulled against the hole by the threaded nut. These anchors work extremely well.
The concrete anchors must be set at least 2-1/4 inches deep. Drill the hole about 1 inch deeper (or 3-1/4 inches total) to allow for dust accumulation at the bottom of the hole.
Mark the minimum depth line on the anchor (blue line) and tap the anchor into the hole. The 3-1/2 lb sledge hammer as shown here is more than enough for the job.
Place the washer and nut on the anchor and tighten. The anchor should grab fast with almost no slippage.
The concrete wedge anchor is set fast and tight:
Install the 4×4 Deck Rail Posts
Drill a 1/2 inch hole in the bottom of the 4×4 posts to slide the post over the anchor pin.
Locate the center of the post by measuring and marking 1-3/4 inches on each side as shown by the black tick marks:
Use a square to mark a straight line across the tick marks on each side to locate the center of the 4×4 post.
The center of the 4×4 post is now located at the cross hair to drill the 1/2 inch hole to receive the pin of the concrete anchor wedge.
Drill a 1/2 inch diameter hole in the center of the post to receive the pin of the concrete anchor. I use Dewalt “pilot” type drill bits that prevents the large drill bit from “walking” when starting the hole. Drill the hole about 4-1/2 inches deep.
Take care to drill the hole vertical (i.e. not canted to the side). I use the carpenters square to periodically check my drill alignment with the post.
Test fit the anchor wedge to verify the hole is deep enough and the hole is vertical with the post.
Place the post standoff over the pin to check the overall fit and assembly:
The post standoffs are attached with four 2-1/2 inch corrosion resistant deck screws as shown.
Set the 4×4 post on the concrete anchor pin to check the overall fit. Repeat for the above procedure for the other post.
This project is continued in How to Build a 2×4 Deck Rail on a Concrete Patio – Part 3.
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