Children love swings, but by building a swing set with clean lines, a subdued material palette and comfortable seating, you can create a popular hangout space for people of all ages. Choose a relatively flat, level site to build the swing set. The area should measure 20 feet wide by 26 feet long or larger and be free of any hard-paved surfaces or obstacles that could cause injury, such as buildings, fences, poles, trees, rocks and overhead wires. (See Reference 1, page 2)
Mark out the 20-foot-by-26-foot area using string, wooden stakes and mallet. Ensure that no underground utility lines run through the area by dialing 811 for a directory of utility companies. Drive two stakes halfway along the 26-feet sides and tie a string between them to bisect the area into two equal halves, each measuring 20 feet by 13 feet. (See Reference 2, 3)
Measure 76 inches along middle string, followed by another 87 ½ inches and mark both locations with stakes. Use a carpenter's level and long piece of lumber to check the slope of the ground between the two stakes. If the height of the ground from one end of the swing to the other exceeds 3 inches, level the area using a shovel.
Dig a post hole with a 20-inch-by-12-inch cross section centered on each of the two stakes in the middle of the swing set area using a post-hole digger or power auger. Orient the long axis of the post hole parallel with the long axis of the rectangular area surrounding the swing set. Contact the local building department to determine the frost depth in your area. Dig the post holes 4 feet deep or 10 inches below the frost depth, whichever is deeper. Flare out the bottom of the post hole slightly. Shovel 4 inches of gravel into the bottom of each post hole and tamp the gravel down with a 4-by-4 post. (See References 4, 5, 6)
Insert the end of a 12-foot length of 4-by-4 cedar or pressure-treated lumber into one of the post holes, resting the post on the gravel. Draw a line across the post to mark ground level. Measure 7 feet upward from ground level and mark the height on the post. Make the same height markings onto a second post. Sandwich a scrap piece of 4-by-4 lumber measuring around 14 inches long between the two posts. Line up the top edge of the spacer with the 7-foot height marking. Insert a second spacer near the posts' midpoints, ensuring the spacer does not extend below the ground-level marking. Clamp the assembly together tightly to create a doubled post with a 3 ½-inch space between the posts.
Insert the doubled post into a post hole. Check for plumb using a carpenter's level. Brace the posts with two lengths of 2-by-4 lumber attached at 45-degree angles to the posts and fastened to stakes driven into the ground. Repeat the steps to install a second, identical doubled post.
Slide one end of an 8-foot length of 4-by-6 cedar or pressure-treated lumber through the centre of one doubled post and slide the other end of the 4-by-6 through the gap in the other doubled post to test if the posts line up properly for receiving the beam. Check that the distance between posts measures 7 feet. Make any slight adjustments to the posts' positions, if necessary, and reattach the bracing. Remove the 4-by-6 beam.
Shovel wet concrete mix into the post holes, filling them around a third of the way. Raise and lower the end of a 2-by-4 in the concrete to release any trapped air bubbles. Fill the post holes with concrete and add an extra 2 inches of concrete above ground level. Smooth the surface of the concrete with a mason's trowel, creating a slight slope to the surface to drain water away from the posts. Let the concrete cure for two to three days. (See References 4, 5)
Measure the distance between the two chain attachment points on a swing seat to determine the distance to space the eye-bolts apart on the beam. Mark the eye-bolt positions on the 3 ½-inch-wide face of the beam, centering one eye-bolt on either side of the center point of the beam. Or, for hanging two sings, mark positions for two eye-bolts on either side of the beam's center point. Ensure that each swing seat will hang at least 8 inches from another swing seat and at least 12 inches from a support pole. (See Reference 1, pages 4, 5)
Drill through the beam at each eye-bolt position with a 1/2-inch drill bit. Thread a washer onto a hot-dipped galvanized eye-bolt that has a 6-inch-long, 1/2-inch-diameter shaft; thread the eye-bolt through the beam and add two washers followed by a lock nut onto the other end of the eye-bolt. Tighten the lock nut with a socket wrench. Repeat the steps to attach eye-bolts to the other holes in the beam.
Lift the beam into place between the doubled posts, resting it on the spacers near the top of the posts. Check the beam for level using a carpenter's level. Adjust the height of the spacers until the beam is level.
Drill two evenly spaced holes through the side of each post, through the beam and out the other side of the other post, using a 1/2-inch drill bit. Repeat the steps to drill two holes near the other end of the beam. Thread a washer onto an 11-inch-long hot-dipped galvanized carriage bolt; thread the bolt through the posts and the beam and add another washer followed by a lock nut onto the other end of the bolt. Tighten the lock nut with a socket wrench. Repeat the steps to attach carriage bolts to the other three holes.
Cut the tops off the posts around 2 to 3 inches above the beam using a hand saw. Make the cut with a slight angle to shed water off the top of the posts. Brush wood preservative over the cut ends of pressure-treated posts. Remove the braces and the 4-by-4 spacers. Spread a 9-inch-deep layer of shock-absorbing material, such as wood chips or shredded rubber mulch in the marked area surrounding the swing set. (See Reference 1, pages 2, 7)
Attach lengths of safety-coated swing chain to the swing seats with heavy-duty hot-dipped galvanized S-hooks. Close the ends of the S-hooks by hammering them against a hard surface. Hang the chains from the eye-bolts in the beam using 3/8-by-3 ½-inch hot-dipped galvanized spring-loaded clips. Ensure that the minimum distance between the shock-absorbing material and the underside of the swing seat is 8 inches. (See Reference 1, pages 3-5)