Deck Railing Process
In addition to providing safety, railings are an important design element of your deck. They help convert the flat surface to a three-dimensional enclosure. For most railings, install the posts first, then the rails, then the balusters, and finally any decorative trim.
Most building codes require railings on decks built 18 inches or more above the ground—in some areas even less than that.
Typical codes also set a minimum height for railings, usually 36 or 42 inches. Your local codes also specify the distance between posts, the openings under the railings, and baluster spacing (usually no less than 4 inches and no more than 6 inches).
MATERIALS: Use the same wood on the railings as you used for the decking. If you have splurged on the decking, maintain that quality in the railings. Using different materials can often destroy the continuity of your design.
EASY DOES IT: You can build railings between the posts using one of three methods.
- Use the same posts that support the deck (extended above the decking).
- Add posts to create the proper spacing between supports—typically 4 to 6 feet.
- Empty posts using a combination of the two methods above.
Finish the posts by making a decorative detail. You’ll want to do this work before you put the posts in. Here are several ideas for creating your own styles:
- With a router or table saw, make band cuts near the top of each post. Chamfer the top of the post at an angle that corresponds to your overall design, and make sure not to make the point dangerously sharp.
- Turn the top of each post into a decorative finial using your lathe or shaper.
- Bevel the bottom of each post with a table saw. You’ll be surprised at how much interest this simple detail will add to your deck design.
In a popular railing installation, and one of the easiest to build, posts are attached to the header and end joists. This system allows you to add the railings after installing the framing and decking. Because you’ll be working along the outside edges of the deck, you’ll have easy access to each post.
If the posts don’t already extend above the deck, add new posts beginning at the house and corners. Attach 4×4 railing posts to the facing at least every 6 feet. Install posts at your stair location, too, cutting their tops to match the stair angle. Installation is the same no matter where you locate the posts. Here’s what you do:
- Mark each post location. Then cut the posts to length and predrill them for Ms hex-head bolts (offset and countersink the holes) or carriage bolts. If you can’t get a bolt in, use lag screws. Then make any decorative cuts.
- Set each post plumb at its location, and run the drill bit through the holes to mark the joist. Drill 5/s-inch holes through the joist (pilot holes for lag screws), and fasten the post in place with 3/sx7-inch fasteners.
- When the corner posts are in place, divide the space between them equally and at a spacing that conforms to local codes. Snap a chalk line between the bottom of the corner posts so their outside faces will lie in the same plane. Then mark, cut, and install the remaining posts using the fasteners for which you predrilled the holes.
Use the same marking methods for top-mounted posts set in anchors on the decking.
Installing Deck Railings
To set the railings, first mark the rail locations on the posts, then cut the rail stock so it will fit snugly.
- Attach the bottom rail first, about 3 inches above the decking.
- Fasten the top rail from the underside or sides to hide the screw holes—flush with the top of the posts.
- Hold side-mounted rails in position and cut the joints so they are centered on a post.
Predrill the rails and drive two 3-inch galvanized decking screws just through the other side. Place the rail at the mark and press the screw tip into the post, then drive one screw at one end and one at the other. Finish by driving all screws home. Alternatively you can attach the railings with rail hangers, or toenail them, using blocks underneath for increased support.
In most areas, building codes require that balusters be spaced less than 4 inches apart. Codes also specify the spacing between the deck surface and the bottom rail. Some railing designs, including those that use screening material or latticework between the posts, have openings small enough to meet most building codes. Others, including many popular designs, should be approved before you start building.
Here are a few ways to reduce the amount of time and effort you spend on installing railings:
- To make the railing parts consistent, cut all the pieces of each kind at the same time, using a 10-inch power miter saw with a stop installed at the length of your finished pieces.
- Work off site on a flat surface—or on your deck if there is room. Cut a plywood scrap and use it as a spacer to set the balusters at a consistent distance apart.
- Instead of toenailing the balusters to the bottom rail, fasten them from underneath with decking screws. This is almost impossible to do once the bottom rail is in place, but it’s easy if you assemble the entire railing section before you install it.
A rail cap protects the cut ends of the posts from the weather and adds an important decorative element to your deck design.
Use a straight 2×6 or 2×8 that is low in moisture content and free of large knots. Buy the longest boards you can find, and center any joints over posts. Bevel the joints and seal the cut ends to reduce moisture damage. The rail caps should be wider than the combined width of a post and rail.
- Position each piece so it overhangs the post and the top rail, and mark it for cutting.
- Attach it with 12d finishing nails or screws driven into the posts—and into the top rail if it is flush with the top of the post—driving a fastener every 8 inches.
- Countersink the screws heads or use a nail set to drive the finishing nails below the surface.
- Fill the holes with putty and sand them smooth.
Outside corners are best mitered to keep them from separating, warping, or splitting over time. To make the 45-degree cuts, use a power miter box or work carefully with a circular saw. Even if you consider your saw accurate, practice on scrap first to get the correct angle. Attach the pieces by drilling pilot holes and driving screws.