How To Build a Backyard Play Set

When it came time to transform our backyard from open ground to playground, we wanted to build a play set that would grow with our kids and remain solid for many years. Theresa designed the structure, and I worked in some construction techniques to make it safe and easy to assemble.

Our children, ages 11 and 3 years old, use the play set for everything from a pretend store to a hideout to whatever their imagination cooks up.

This is an advanced project, but it's fun to put together. If you don't want to build an exact replica of our play set, you can take some of the ideas shown and apply them to your own design. Before you break ground, check your local building codes in case a permit is required for your structure.

Play Set Foundation
Because it has two levels, this play set is heavy. A stable, water-diverting foundation is critical. First, we marked the location of the structure using strings to measure an equal distance between our fence and driveway. (Make sure to maintain safe clearances to hard surfaces.) Next, we leveled the area. In a yard with even a shallow pitch, a play set as long as this (30 ft.) will require you to move some dirt.

The next step is to create a pad of pea gravel, stone and stone dust on which the structure can rest. We removed the grass and leveled the dirt. We then created channels filled with 2-in. stones and pea gravel. This method creates a surface that resists compression and allows water to drain instead of turning the ground into mud. We filled in between the channels with dirt to lock the stone in place. The stone dust on top creates a dependably flat surface on which we placed the base.

LEARN MORE: Don't want to start from scratch?

Here's how to build a play set from a kit.

Base
We framed the base using pressure-treated 4x4s. Only 4x and 6x pressure-treated lumber is rated for ground contact (unless you special order ground-contact 2x boards). This approach spread out the towers' load over a wider surface area.

Once the foundation was level, we started building the base. It is framed square to the exterior dimensions of the tower above. It's fastened using 6-in. exterior-grade structural screws, and its members rest directly on the foundation.

Floor joists
When it came to adding floor joists, we framed the perimeter first. The box is 3 in. smaller than the 4x4 base on all sides so it has a 1-1/2-in. reveal all the way around. We squared it by measuring diagonals with tape measures and making slight adjustments. (A framing square isn't accurate enough.) We fastened diagonal braces across the corners and secured joists inside the frame at 16 in. OC.

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When placing the joist assemblies on the base, we used a scrap 2x block to ensure a uniform 1-1/2-in. reveal. Then we toescrewed the joists to the base.

Corner posts
We could have used 6x6 posts on this project, but they didn't quite fit the design. Instead, for both aesthetics and utility, we fabricated our own corner posts by fastening a 2x8 at a right angle to a 2x6 using a super-stable L bracket that is 7-1/2 in. long on one flange and 7 in. long on the other. We then fastened, plumbed and braced the corner posts to the floor-joist assembly (a two-person job). Next, we drilled holes for and then finger-tightened galvanized bolts through the posts and band joists.

Interior cleats and Tower A
Inside each corner post we installed two cleats that run from the top of the deck surface (not the joists, but 1-1/2 in. above the joists) to the bottom of the second-level joist assembly. The cleats provide structural support for the second level, and because they extend about 1 in. beyond the corner posts, they serve as a fastening surface for the 2x6 siding. Before screwing the cleats directly to the corner posts, make sure you install a deck board underneath them so you'll still have access to the corner-post bolts.

With the cleats in place, installing the 2x6 band joists for the second level is easy. Cut them to the same dimensions as the first-level floor joists and rest them on the cleats. Fasten them to the corner posts. In-fill with joists spaced 16 in. OC, drilling holes for and finger-tightening the through bolts.

Double-check that everything has remained plumb (you may need to rack the structure a little), and cinch all bolts tight. We used an impact driver on one side and a ratchet on the other when tightening the bolts.

Porches and decking
We framed the porches in the same manner that we framed the floor joists, making square boxes and infilling with joists. Before installing them, we filled in the gap between the corner posts with a filler joist screwed to the band joist. We then fastened the porch framing to the tower with structural screws and topped it with 2x6 decking.

Pergola detail
To give the play set a little grown-up panache and to tie the tops of the corner posts together on Tower A, we crafted a pergola detail. We fastened a girder to each side of the corner posts and then installed 24-in.-long rafters. Note: Because we were fastening to an L shape, we used through-bolts where the longest side of the L met the girder. On the other side, we drilled holes for and fastened with two 4-in. structural screws. Then we cut and installed caps to protect the end-grain of the corner posts.

Tower B
Tower B is assembled in the same way as Tower A except for a few minor differences. First, it's smaller. Second, it's centered off of Tower A by 11 ft. 6 in. To find its location, run strings from the far sides of Tower A along the edges past where Tower B is located. This will project the width of Tower A accurately to the second tower location. Next, build a 4x4 base centered between the strings. Finally, build a foundation and base and build up.

Tower B has no pergola detail; the corner posts are held stable by the guardrails, a bridge and a slide. The slide and swings were purchased at a local home center and assembled on site.

Door and window openings
The 24-in. openings are framed by running a 2x4 on-the-flat from the top of the deck to the bottom of the second level's band joist. Drill pilot holes and countersinks for the fasteners, toe-screwing for a solid connection. We laid out the 2x4 studs' positions in the wall by centering them in the space. Find the center of the wall, mark 12 in. on each side of the centerline and then run each stud plumb up from the mark. Reserve some siding to create the top and bottom of the window. We also used some leftover material to create door headers and sills.

Siding
The siding is 2x6. Unlike regular siding, we started installing it at the top and worked down to prevent notches and hide the rip cuts. Setting up a stop on a miter saw will increase accuracy and save time when cutting the siding. Drill pilot holes and countersinks to prevent splits if necessary.

Bridge
Each bridge girder is made of a double 2x6 and a 2x12, making the entire assembly 34-1/2 in. wide — the same as the opening between the corner posts in Tower B. The inside 2x6 holds the monkey bars, which are 1-in. galvanized gas pipe with a flange on each side. (I built this first on sawhorses and then installed it as one piece.) The flanges are screwed 12 in. apart down the center of a 2x6. You don't have to be finicky — the gas pipe isn't exactly precision-machined.

Guardrails
We built the guardrails according to code, spacing the 2x2 pickets 5 in. OC. We fastened the bottoms of the pickets with screws to the tower and porch band joists. We used L-bracket corner posts on the porches, too. These are 2x4 and 2x6. The top-rail cap is a detail you'd find on most well-built decks. The bridge guardrails are fastened to each tower, helping to tie the structure together.

Ladder
The ladder is built out of 2x6 rails and steps. Finding the angle was somewhat arbitrary. We screwed a 2x6 to the side of the porch and Tower A with the bottom edge flush to the top of the second-level decking. We leaned it at an angle that provided ample room to mount the ladder at the bottom. With it in position, we marked the top and bottom, scribing it so it would hook over the tower's deck. We used structural screws at the bottom and deck screws at the top. The steps are spaced 8 in. OC.

Finishing touches
We built the play set out of pressure-treated Southern pine; you could also use cedar or redwood for a different look. Whatever wood species you choose, we recommend sealing it. We used a deck, fence and siding sealer, which provided great coverage in a single coat.

The last step was to add some fun stuff: drums, a telescope and a bell. Both of our kids spend a lot of time with these items, and they love to run and play on all of the features of this well-imagined, solidly built structure.

Theresa and Mark Clement are home-improvement experts and hosts of the online program MyFixitUpLife.