How to Brace a Deck from Swaying

When we built a new deck off the back of our home two years ago, I was pretty excited. A deck is undoubtedly a great addition to any home. However, if you’ve ever walked out onto someone’s deck, only to feel it start rocking back and forth, you don’t need me to tell you that it’s not a great feeling. If you’re dealing with this issue, I’m going to share a few simple tips for how to brace a deck from swaying.

Bracing a deck is extremely important to maintain the integrity of the structure and to ensure your outdoor space is safe for you, your family, and your guests. 

In order to brace your deck, there are a few tips to keep in mind. You won’t need a ton of materials, and the process is fairly simple: 

  • Identify where you’ll be positioning the braces, and measure the distance 
  • Cut the braces on a 30 to 45-degree angle 
  • Attach the braces using structural screws 

I’m going to go pretty in-depth about the process of installing diagonal braces, as they’re the most common and generally the easiest to install. However, I’ll also discuss different bracing methods based on the height and type of deck you’re dealing with. 

How to Brace a Deck from Swaying

Are Deck Braces Necessary? 

You might be thinking that a slightly wavering deck is no big deal. As long as the footings are solid and the deck boards were laid correctly, what’s the issue? Unfortunately, there’s a pretty big issue. Choosing not to add braces to your deck can have dire consequences. 

Failure to properly brace a deck can result in the structure collapsing. With people constantly milling about on a deck that isn’t properly supported, it’s easy to see how this could potentially happen.

When people exit your house and walk onto your deck, it creates a parallel movement, causing that noticeable, sideways sway. Over time, environmental factors like strong winds can also cause the deck to push against the walls and sway, furthering the risk of collapse.

If you live in an earthquake or hurricane prone area, your deck will need as much structural support as possible. 

In order to fulfill the majority of current deck building codes, it is best practice to fasten the deck to your house, rather than leave it as a freestanding structure. This strengthens the structural integrity, but will still require some form of bracing.

Before building a deck, ensure you have the required permits – it would be a real shame if you had to take down the structure and rebuild it. And trust me, I’ve seen this happen a bunch of times.  

Deck Bracing Techniques

As previously mentioned, diagonal bracing is one of the most common and widely used forms of bracing. This involves fastening a 4×4 piece of wood to a 6×6 column, as well as the underside of the deck’s beam.

When finished, you’ll have a “V” shape on either side of the column. Diagonal bracing is generally suitable for all standard-size decks. 

Cross bracing is another bracing option. However, this type of bracing is typically only used to secure decks that are not fastened to a structure. It involves creating an “X” shape by fastening a 2×4 or 2×6 piece of wood on either side of the 6×6 column.

The reason cross bracing is generally only used on freestanding decks is because it provides one of the best forms of anti-sway lateral support, which a freestanding deck needs more than a secured one. 

For decks 6’ to 8’ or taller, installing a continuous footing and wall is generally the most structurally safe option. This method involves pouring a continuous concrete footing, then building a wall (consisting of pressure-treated studs and pressure-treated plywood or skirting material) between the footing and main beams.

A wall promotes lateral strength in each direction, leaving the deck structurally sound and free of sway. This will take more time, but it can be a huge structural benefit to a larger deck.  

How to Brace a Deck from Swaying 

Materials You’ll Need:

Before starting a diagonal bracing project, you’ll need the following tools and materials:

Step 1: Measure the distance between your deck’s column and beam using a 30 or 45-degree angle as your guide. Using a 30 or 45-degree angle promotes the highest amount of structural strength, so it’s really important to stay within this limit. 

Step 2: Once you’ve measured the distance and have identified the angle you’ll be cutting on, use a 12” miter saw or hand saw to cut the 4×4 posts that will act as your braces. Always wear safety glasses before starting any cuts. 

Step 3: With the braces measured and cut, it’s time to fasten them. If you’re using structural screws that are 5/16 thick x 6” long, you’ll need two screws per brace side. With either an impact driver or drill, fasten the screws into the post and through the column, perpendicular to the brace.

When you’re done fastening the post to the column, repeat these steps and screw the post to the deck’s beam. 

Step 4: Ensure you’re fastening the diagonal posts on either side of each column around the entire perimeter of your deck. This form of structural support holds the deck together, preventing that pesky swaying and preventing a potential collapse.

Deck Bracing Techniques

Now you’ll be able to enjoy your deck stress-free, knowing that it’s secure and safe for people to walk on! 

How to Brace Underneath a Deck

While diagonal bracing from your deck’s columns to beams is a sure way to promote structural integrity and prevent movement, you can also install bracing underneath a deck to stop the sway. Bracing underneath your deck involves a method called angle bracing, and it can be done using a few 2x4s, and some 16d galvanized nails.

When bracing underneath a deck, you’ll need to use nails, not screws. Nails (especially your 16d common nail) have shear strength, meaning they’re far less likely to move laterally when compared to a screw. 

To brace the underside of your deck, all you need to do is fasten a pressure-treated 2×4 diagonally from corner to corner on an angle. You’ll need to drive in two 16d nails at every point in which the 2×4 meets the deck’s joists.

If the underside of your deck is too large to use a single 2×4, use two 2x4s. You should overlap the two 2x4s by two joists, at the very least. When you’ve finished fastening the 2x4s to the underside of your deck, cut the overhang flush with the edge of your deck. 

If you have a nail gun, using it will make fastening the braces quicker. However, just a plain old hammer will also do the trick. If you can enlist someone to help hold up the 2×4 as you drive in the first set of nails, this will also make the job a little bit easier. 


Take  a good, hard look at your deck. To ensure your deck is structurally sound and safe for people to walk on, bracing (either diagonal, cross-bracing, or with a continuous footing and wall) is a necessary precaution. Bracing will also protect your deck from the elements and greatly reduce the risk of a structural collapse. 

If you’ve found that this article answered your deck bracing questions, please leave a comment and let us know! If your friends or family have questions about bracing their decks, be sure to share these insider tips with them.

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