How to Build a Playground: Step 3 – Bracing and Blocking

April 17, 2021May 25, 2021 by Peter In Playground 7 Comments

Step-by-step instructions for structurally strengthening your playground with bracing and blocking.

Picking up from the previous step (where we added deck boards to the towers and bridge), now we will add bracing and blocking to the playground frame. Free-standing structures like this playground are incredibly prone to you racking, which is lateral sway or side-to-side movement of a structure. If you walked on top of the playground deck/platform after Step 2, you almost certainly would have noticed minor racking.

Racking can be very dangerous. If you imagine five or ten children running every which way on the playground, swinging in different directions and using the monkey bars too – all this force and movement could bring down the playground. Fortunately, racking is easily prevented with bracing. We’ll further eliminate the potential for racking with blocking. After both bracing and blocking, the playground structure will be rock solid. Adults could have a dance party up on the playground deck/platform and it wouldn’t budge a bit.

This picture illustrates bracing (white arrows) and blocking (red arrows) on the actual playground:

Bracing and blocking on a playground — Bracing (white arrows) and blocking (red arrows) on the playground.

In CAD, bracing will look like this (shown in yellow):

Diagonal knee bracing in yellow on a playground — Playground construction in CAD: bracing (shown in yellow).

Also in CAD, blocking will look like this (shown in green):

Blocking in green on a playground — Playground construction in CAD: blocking (shown in green).

This is the 3rd post of my step-by-step How to Build a Playground series. You can read the other posts in this series through these links: Step 1 – Towers and Bridges, Step 2 – Deck Boards, Step 4 – Swings and Monkey Bars, Step 5 – Railing, Step 6 – Rock Climbing Wall and Step Ladder, Step 7 – Step Ramp, and Step 8 – Staining Wood. This series will show you how to build a playground that looks like this:

Large playground stained brown with two green slides, swings, and monkey bars — Learn how to build a playground that looks like this!

There are additional posts and a separate six-part series covering the fundamentals of building a playground; you can explore those on my Playground page.

Bracing Overview

Bracing is a piece of wood fastened between two structural components, and its purpose it to keep the structure from moving – thus eliminating racking and stabilizing the frame. Diagonal “knee” braces cut at 45 degree angles are the most effective way to resist racking (that is what I used on my playground). The taller the structural posts, the longer and more substantial the bracing should be.

In terms of the lumber used for the braces, I used any remaining or scrap 2×6 deck boards leftover from Step 2. After that, I used 2x4s to finish the bracing. Each tower will need 8 braces (my tower on the left only has 7 braces since the extra post for the monkey bars prevented the addition of the 8th brace).

To make the braces, you will need a circular saw, hammer, and the angle finder (digital) from my Materials & Tools post. You’ll need the KBS1Z Simpson Strong-Tie Knee-Brace Stabilizer, nails: (.131 x 1-1/2 Inch and .131 x 2-1/2 Inch), and 8 inch timber screws from my Connectors & Fasteners post. I used the 1-1/2 inch nails when hammering into 2x lumber, and the longer 2-1/2 inch nails when hammering into 6×6 posts or double 2x support beams.

Note that even with a KBS1Z nailed in, the bracing felt a little insecure so I also screwed in the bracing with 8 inch timber screws. After that, the bracing felt very strong and sturdy. Nails have better shear strength and screws have better tensile strength, so you cover both forces by nailing and screwing the brace in. Read this link for nails vs. screws and shear vs. tensile strength.

Step 1: Determine the Length of the Brace

When determining the length of a brace, it’s helpful to keep in mind that you’re basically creating a triangle. I wanted 3 ft. sides for my bracing triangle (sides b and c in the triangle below), which meant my brace (the hypotenuse of the bracing triangle, side a) would be about 4.25 ft. This is a good triangle calculator for helping determine the lengths of braces, which shows my 4.25 ft. brace length:

Triangle used to calculate diagonal knee brace lengths — 3 ft. sides yield a 45 degree diagonal knee brace approx. 4.25 ft. in length.

Step 2: Cut the Braces to Size

On the lumber for your bracing, measure and mark the desired brace length (4.25 ft. for my playground). Then use the digital angle finder set at 45 degrees, and trace out the 45-degree cut. Use the circular saw to cut the brace at the 45-degree angle.

How to cut a wood board for diagonal knee bracing — Cut the braces to size.

Step 2: Use the KBS1Z and Nail in the Brace

Each brace requires two KBS1Zs. If you can, it’s helpful to have someone hold the brace while you fasten it in. On the playground tower, bracing will go in between a 6×6 post and a double 2x support beam or a 6×6 post and a single 2x rim board. As I mentioned before, I used the .131 x 1-1/2 inch nails when hammering into 2x lumber and the longer .131 x 2-1/2 inch nails when hammering into 6×6 posts (pictured below) or double 2x support beams.

Simpson Strong-Tie KBS1Z knee brace stabilizer nailed into a playground — Use the KBS1Z and nail in the brace.

Step 3: Screw in the Brace

With the bracing nailed in, further secure it with 8 inch timber screws (one on each end of the brace), like this:

8 inch timber screws further secure diagonal knee bracing to a playground — Screw in the brace using 8 inch timber screws (one on each end of the brace).

Blocking Overview

Blocking is a piece of wood fastened between joists, and its purpose is to prevent joists from twisting or rotating. Blocking (in green) is pictured in between two joists (in red) here:

Blocking in green helps prevent joist rotation — Blocking (in green) between two joists (in red) prevents joists from twisting or rotating.

Blocking is often installed at the midway of a deck in an alternating or staggered manner (to allow enough room for successive blocks to be screwed in to the joists). It’s often cut from the same dimensional lumber as joists (so if the joists are 2x10s, then the blocking will be cut from 2x10s too).

To make blocking, you will need a circular saw and joist flashing tape (from my Materials & Tools post), and 4 inch deck screws (from my Connectors & Fasteners post).

Note that in addition to the tower joists, you will also need to add blocking to the bridge joists.

Step 1: Cut the Blocking to Size

The exact size of blocking will be determined from your joist spacing. Measure the distance in between joists, then use a circular saw to cut blocking to size from the same dimensional lumber you used for the joists.

Step 2: Place Joist Flashing Tape on the Top Side of Blocking

Similar to placing joist flashing tape on top of joists (as we did in Step 1), you will want to place a strip of flashing tape on the top side of the blocking (the side that will touch the underside of deck boards).

Step 3: Screw in the Blocking

Go about midway under the deck/platform or bridge, and start screwing in the blocking to joists in an alternating or staggered manner. The reason you alternate/stagger blocking is to allow enough room for successive blocks to be screwed in to the joists.

I used four total 4 inch deck screws per block (two per side). Screwing in the alternating/staggered blocking looks like this (screws illustrated by white arrows):

Fastening blocking to a playground using screws — Screw in the blocking to joists using 4 inch deck screws (white arrows).

Next Step

Congratulations! You now have a rock solid playground structure ready for tons of use from your children and their friends!

In the next step, we will add the swings and monkey bars.

Did you find this guide useful? Have you built a playground or play set? Let me know in the comments below!

Read the other posts in this series: Step 1 – Towers and Bridges, Step 2 – Deck Boards, Step 4 – Swings and Monkey Bars, Step 5 – Railing, Step 6 – Rock Climbing Wall and Step Ladder, Step 7 – Step Ramp, and Step 8 – Staining Wood.

Explore more at ProjectsByPeter.com/Playground