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 Part 1.
Install Concrete Anchors for the 4×4 Posts
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.
Build a Deck Rail: Drill the Hole for the Concrete Anchor
I used 1/2 inch x 5-1/2 inch threaded concrete anchors as shown. I bought mine from Home Depot.
Red Head – Trubolt Concrete Wedge Anchor 1/2″ x 5-1/2″
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.
Red Head – Trubolt Concrete Wedge Anchor
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.
Build a Deck Rail on a Concrete Patio: Check Hole Depth for Concrete Anchor
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.
Build a Deck Rail on a Concrete Patio: Install the Concrete Anchor
Place the washer and nut on the anchor and tighten. The anchor should grab fast with almost no slippage.
Build a Deck Rail: Concrete Anchor Bolt for the 4×4 Post
The concrete wedge anchor is set fast and tight:
Build a Deck Rail: Concrete Wedge Anchor
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:
Build a Deck Rail: Measure 1-3/4 Inches to Locate the 4×4 Post Center
Use a square to mark a straight line across the tick marks on each side to locate the center of the 4×4 post.
Build a Deck Rail: Mark a Line at 1-3/4 Inches per Side of 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.
Build a Deck Rail on a Concrete Patio: Center of 4×4 Post Marked
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.
Build a Deck Rail: Drill a 1/2 Inch Hole for the Concrete Anchor
Test fit the anchor wedge to verify the hole is deep enough and the hole is vertical with the post.
Build a Deck Rail: Trial Fit the Concrete Anchor
Place the post standoff over the pin to check the overall fit and assembly:
Build a Deck Rail on a Concrete Patio: Post Standoff and Concrete Wedge Anchor
The post standoffs are attached with four 2-1/2 inch corrosion resistant deck screws as shown.
Fasten the 4×4 Deck Post Standoff with Screws
Set the 4×4 post on the concrete anchor pin to check the overall fit. Repeat for the above procedure for the other post.
Build a Deck Rail on a Concrete Patio: Set the Post on the Anchor Pin
This project is continued in Part 3.
Thanks for reading!
Bob Jackson
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Hi, nice write up! I have a question. I am redoing my front porch railing. The porch is concrete bordered by two rows of brick. I need to attach the railing 4×4 post on the brick between my main porch support posts. The original 4×4’s were just glued in place and provided no lateral stability and have long since came loose. I understand that i cant use wedge anchors in brick, so what options do i have? Would it be best to just insert a threaded rod in a chemical fastener and install as you outlined above or are there other options that would be better such as a single expansion anchor Thanks.
> … would it be best to just insert a threaded rod in a chemical fastener …
That sounds reasonable. Choose your anchor, drill a hole through the brick (not the mortar joint) and set the anchor with Simpson Strong-Tie(R) epoxy anchoring adhesive. The Simpson Strong-Tie products are available at the big box home improvement stores. Choose a longer anchor – say 8″ or even 10″ long – to better distribute the load through the brick.
The Simpson Strong-Tie site has a nice graphic for setting anchors in brick.
> or are there other options that would be better such as a single expansion anchor
An expansion, or wedge anchor, would crack the mortar joints and split the bricks. You’re thinking is correct that wedge anchors shouldn’t be used with brick.
Thanks for reading,
Bob Jackson
Thanks for the prompt feedback, it is much appreciated!
Bob,
Great post. I have one question. How do you secure the wedge anchor to the 4 by 4 post? The way I interpret the project description it is not clear to me whether the posts are glued to the anchor. What keeps them from being pulled right off?
Thanks
Brian
The 4×4 deck rail posts simply slides onto the concrete anchors. What keeps the posts from being pulled up & off are the top and bottom horizontal rails are fastened to the 8×8 inch support posts, or for the small deck rail section built in the project it’s the Simpson Strong-Tie steel angle connector fastened to the deck stair support post that prevents it from being pulled up – and also stabilizes the panel against back & forth wiggle.
If your concrete deck does not have existing support posts to attach the ends of the deck rail panels, you could fill the drilled hole in the bottom of the 4×4 deck rail post with construction epoxy to securely bond the panel to the concrete wedge anchor.
this is great info thank you. How does this hold up with back and forth wobble. I am thinking of doing this on some blue stone over laid concrete stairs at an elderly house. Do you have any other recommendations?
A concrete wedge anchor and plastic post base standoff alone doesn’t provide enough rigidity against back & forth sway. The rail ends need to be fastened to a wall or between support posts so it doesn’t give when the rail is leaned against or pushed.
Something like the Simpson Strong Tie FPBB44 Black Powder-Coated 12-Gauge E-Z Base would be stronger but not as attractive and you’d need to have a licensed engineer certify the design meets your local building code.
Since your working on concrete stairs you could drill holes for 1/2 inch wedge anchors installed on the side of the stairs then bolt on the 4×4 guard posts. Use two anchors per guard post similar to building a wood deck rail. I think that would be much stronger and have better odds of approval by a licensed engineer.