How to Build a 2×4 Deck Rail on a Concrete Patio – Part 2

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:

  1. Locate the right post and mark the center as shown below.
  2. Measure 39-1/2 inches to the left and mark the center of the other post.
  3. 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

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"

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

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

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

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 4x4 Post

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

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 4x4 Post Center

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 4x4 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 4x4 Post Marked

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

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

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

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 4x4 Deck Post Standoff with Screws

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

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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5 Responses to How to Build a 2×4 Deck Rail on a Concrete Patio – Part 2

  1. allen May 6, 2010 at 11:09 am #

    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.

    • Bob Jackson May 6, 2010 at 6:44 pm #

      > … 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

  2. allen May 7, 2010 at 6:20 am #

    Thanks for the prompt feedback, it is much appreciated!

  3. Brian September 6, 2012 at 9:19 pm #

    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

    • Bob Jackson September 7, 2012 at 7:22 am #

      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.

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