How to Build a Deck Railing in 10 Steps
Putting the finishing touches on your deck requires precision and skill
- Wrench
- Tape measure
- Chalk
- Circular saw or miter saw
- Clamps
- 4x4 pressure-treated lumber
- 2x4 pressure-treated lumber
- 2x2 pressure-treated balusters
- Deck bracing (optional)
- Deck anchors
When refurbishing a deck or building a new one, a railing is a key part of the project. It creates a finished look and helps the deck adhere to safety codes, since a deck railing is required if your deck is at least 30 inches off the ground. Knowing how to build a deck railing gives you a project you can take pride in whenever you step outside. Let’s walk through the steps.
Evaluate Your Deck Frame for Stability
Photo: msderrick / E+ / Getty ImagesDeck railings require a stable foundation. If you're adding or replacing railings on an existing deck, thoroughly inspect the frame for common deck problems that require repair.
Your deck's ledger board, the horizontal board that attaches the deck to your home, should be securely bolted to the house. If not, tighten bolts and reinforce weak spots. With the frame attached, inspect the joists for sagging or warping. Add deck anchors and bracing as needed.
If you discover serious structural problems, stop your deck railing project here and call a pro to repair your deck frame before you continue.
Measure and Set Spacing for Posts and Railings
To build a deck railing, you can use 4x4 lumber for your deck posts, 2x4 lumber for your railings, and 2x2 lumber for your balusters. To determine optimal lengths and spacing for your posts and railings, keep the following in mind:
Most building codes regulate deck railing post spacing and height.
Most codes allow no more than six feet between posts, measured from the post’s center.
Most codes require deck railings to be at least three feet tall above the deck surface.
The bottom of each post should be flush with the bottom edge of the end joist.
Plan on having posts by the house, outside corners, and the tops of staircases.
Determine the number of posts you'll need between two corners by measuring the distance, dividing by your spacing, and subtracting one. For example, if the distance between corners is 18 feet with six feet between posts, divide 18 by six. The result is three. Minus one is two. This means you'll need two posts between the corners. Mark where each post will go using chalk.
Cut the Posts to Size
Photo: AleksandarNakic / E+ / Getty ImagesWith your measurements in hand, don your mask and safety glasses. Use your saw to cut each post to length, accounting for the full height of the post from the bottom of the end joist to the height above the surface, as required by your local building codes.
Place the Post
Place your first post in the location you marked with chalk and use clamps to keep it in position. Screw the post in place flush with the bottom of the end joist, making sure it's plumb.
Attach Bracing and Deck Anchors Inside the Joists
Access the joists from below or by removing the decking boards around the post. Use a drill and deck screws to install extra bracing by the post between the end joist and floor joist if there isn’t a brace already.
Line up an anchor about two inches from the top of the joist and flush with the brace. Attach it to the bracing with screws.
Bolt the Post in Place
Drill a hole through the anchor into the post. Run a carriage bolt through it to secure the post with a washer and nut. Use your wrench to secure the connection tightly.
Drill a second bolt hole through the post and joist about two inches from the bottom of the joist and run a second carriage bolt through, again securing it with a washer and nut.
Secure the Remaining Posts
Repeat the previous three steps until all of your posts are securely fastened to the end joist. Reinstall any decking boards you removed.
Add the Top and Bottom Deck Rails
Photo: K Neville / iStock / Getty Images Plus / Getty ImagesClamp the lumber for the bottom rail to the posts at about 3.5 inches above the decking surface. Secure the rail to the posts with decking screws. Do the same with the top rail, making the top of the rail flush with the top of the post.
Install Balusters
Refer to local codes to determine the required spacing for balusters. Many codes require a spacing of 3.5 inches, or about 3 balusters per foot. Drill pilot holes in the top and bottom of each baluster in alignment with the top and bottom rails, then secure them using nails.
Install Post Caps and Trim
Photo: Bryan Chavez / iStock / Getty Images Plus / Getty ImagesTop your posts with post caps and add trim skirts at the bottom of each post to conceal gaps and add moisture protection.
Mistakes to Avoid
Deck railing installation is an intensive project with a lot of steps. Even if you have the necessary tools and carpentry skills, you'll still want to look out for several mistakes that DIYers commonly make:
Using the wrong hardware: Ensure that your screws, nails, carriage bolts, washers, and nuts are all rated for pressure-treated lumber.
Ignoring building codes: To ensure that your railings are adequately supported and meet safety standards, follow local building codes.
Overlooking instructions: Many pre-made railings and infills include manufacturer recommendations—the instructions that come with your product should be your primary source of information over other guides.
DIY vs. Hiring a Pro
The cost to replace deck railings as a DIY project varies by the size of your deck and the quality of the materials, but you can expect to spend at least $500 and about $950 on average. Compare that to the cost of hiring a pro for the job, which averages about $1,100 but can range anywhere from $650 to $3,400, and you can see the potential savings DIY can afford.
However, installing deck railings safely and properly requires specific carpentry skills, tools, and knowledge of local building codes. Mistakes can result in a finished project that doesn't last or compromises safety for you, your family, and your guests due to wobbly railings. Ensure the job gets done right the first time by contacting a few local deck builders for estimates.
Frequently Asked Questions
Apply a wood stain or sealant to properly maintain a wood deck railing and keep it looking new. Sealants protect wood from moisture and weathering. Regularly inspect the railing for loose screws, damaged balusters, and other signs of wear to make timely repairs. Routinely clean the railing using mild soap, water, and a soft bristle brush.
The four-inch ball rule for railing is a rule of thumb used when installing or replacing railings on stairways and decks. It refers to the gaps that naturally occur between balusters or other infills in a railing system. The rule states that a four-inch sphere should be unable to pass through any of the gaps. This helps prevent the possibility of people or animals slipping through.
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