Start building the frame for your freestanding deck with this guide to beams, headers, and outside joists.

January 26, 2019

When you're building a deck, few things are as exciting as seeing your plans come to life. All the prep starts to pay off as you begin to build the frame. This tutorial shows you how to build deck beams, headers, and outside joists. These crucial parts give your deck strength and stability, and lay the framework for the finished product.

What You Need

  • Beams
  • Pencil
  • Level
  • Post/beam connector or T-brackets
  • Joist-hanger screws
  • Clamps
  • Measuring tape
  • Drill
  • Nails or screws
  • 3-4-5 triangle
  • Braces
  • Seismic ties

Step 1: Mark and Place Beams

Mark the beam where it will overhang the posts on both ends. In this case, the beam is marked 3 feet from each end. Then have someone help you place the beam on top of the posts. For the longer beams, you may need two helpers. Make sure that the beams are flush to the posts on both sides.

Step 2: Check for Level

Check the beam for level. If it isn't, trim one of the posts. If trimming will lower the deck too much, cut and install a new post; do not shim the beam to level it. Attach the beam to the post with a post/beam connector or with T-brackets and joist-hanger screws on both sides.

Step 3: Cut and Mark Joists

Cut the two header joists to length. Use the straightest boards possible. Clamp them together on a flat surface, side by side, with crowns facing in opposite directions and the ends perfectly aligned. Mark the headers with the joist locations indicated on the framing plan, 12 inches apart in this example. Every 12 inches, make a V-shape mark. Draw square lines through the marks as shown. Draw an X on the joist side of the line.

Step 4: Square and Attach Corners

Cut the outside joists to length—usually the width of the framing minus 3 inches for the thickness of the two headers. On a flat surface, assemble the outside joists and the headers. Make sure the headers face each other correctly with their crowns up and the Xs on the same sides of the layout lines. Use a framing square to check that the frame is square. Drill pilot holes and drive nails or screws to attach the boards at the corners.

Step 5: Square and Brace

Check again for square, using a 3-4-5 triangle. Attach a temporary brace at each corner to keep the frame stable when you lift it up. For the brace, use a 1x4 or larger, and attach it with two screws at each joint.

Step 6: Measure and Attach Frame

With a helper or two, lift the frame and set it on top of the beams. Measure the frame at all four points to make sure it overhangs the beams by equal amounts on all sides. Check again for square with a 3-4-5 triangle. Attach the frame to the beam with a seismic tie or similar hardware at each joint.

Framing Overview

A framing plan, such as the one shown here, shows the exact location of every joist. Make one for your own deck project, and pay attention to details, such as the exact length of the headers.


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