How to Build a Deck: Part 5

In the final video of our decking series, you’ll learn to build stairs and railings for your deck.

Railings & Stairs

The final step is to build stairs and a railing for your deck. Determining stair size is a bit of a science, and here’s another instance where you should consult a good resource and local building codes to get all the details and formulas you’ll need. A good general rule about outdoor stairs is this: Twice the riser height (the vertical part of a step), plus the run of the step (the horizontal part) should equal between 24 and 27 inches.

Build Steps at Least 3 Ft. Wide

Another rule about outdoor stairs is they should be at least 3 feet wide for ease of traffic flow and safe use. Most codes require a 3-foot minimum anyway. Once you’ve done the math and figured out how many steps you need, you’ll need to cut stringers. Stringers are the wooden frames for the steps. You’ll use a framing square to transfer the measurements to a piece of lumber. On our deck we’re using 2 x 12’s. After you’ve marked off all the steps, use a circular saw to cut most of the way, and a jigsaw to finish. You don’t want to cut past the mark in the corner because this will weaken your stairs.

The good news is that once you cut one good stringer, you won’t have to measure again. Simply use the first stringer as a template for the others.

You need to assemble the stairs on the ground first. This allows you to locate your posts and set the stair height accurately. Continue installing stringers 16” apart for the width of your stairs. If you’re so inclined, this is the time to install risers, or the vertical part of the stairs. For our deck, we’re leaving the risers open.

Now we need to attach the stairs to the deck. First, we install a stair hanger or crossbrace, constructed from 2 x 10s. Temporarily attach your stairs to the deck to mark the locations for your postholes. Now we’re going to mark our postholes, pour the concrete, place our posts, level them and finally, attach them to the stairs.

Attach Tread

For the treads, we use decking boards for a coordinated look. We attach the treads with deck screws, then we’ll notch the bottom tread around the post for a nice finished look. To finish our deck we need railings. Most building codes require railings for decks over 24 inches in height and most codes require these railings to be at least 42 inches high. We divide the spacing of the posts to create equal distances for each rail section. The posts may be positioned anywhere between the joists.

Attach Railing Posts

We box in the post to the framing using the rim joist as the front support and blocking to support the back and sides if required. The blocking should be the same dimensions as the joists. Now we mark the location of each post, drill a pilot hole and then cut out the post location with a jigsaw. Between posts, we install rails so that we will have something to attach the balusters or pickets to. We are using 2 x 4’s for our top and bottom rails. Now we can install the plastic mounts that came with your railing kit and attach the bottom rail.

Once the rails are screwed to the posts, we can attach the balusters. By code, balusters have to be close enough together so that a 4-inch sphere can’t pass between them. After the top and bottom rails are in place, we use a circular saw to cut the top off the post to make it flush with the rail. Repeat the process for the rest of the deck rails.

Now all we need to do to finish the railings is to install the top piece, called the cap rail. On our deck we will be using 2 x 6’s for this. We lay the cap rail over the balusters and posts and attach it with decking screws. We continue this around the perimeter of the deck, mitering the joints where cap railings meet.

As a nice finishing touch, we make angle cuts, or dog ears, on the corners of the cap rails. At this point, your deck is 99% done, but there are still a few finishing touches that you can do to make it even sturdier and last longer.

Finishing Touches

Start by adding structural post-to-beam supports to every post, then bolt the cradles to the posts with lag bolts. Finally, apply sealer to the cut ends of boards to help protect it from weather and insects.

You now have a completed deck built with pressure treated lumber. If you use pressure treated lumber, you’ll want to protect your deck.

Protect Your Deck

Periodic application of a high-quality, clear water repellent or semi-transparent stain with water repellent helps to minimize warping, splitting, and other weathering problems. You may need to wait a certain period of time after you build your deck to apply the sealer or stain because pressure treated wood is wet when new. Consult your wood manufacturer’s recommendations on any waiting times. Remember, it’s important to regularly maintain any deck, no matter what it’s made of.

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