Deck Bridging [What You Need To Know]

If you want to build your own deck for your home or just as an outdoor project, then you need to learn all the different steps and techniques used so you can build a functional and safe-to-use deck. 

One such technique is deck bridging – but what is it, and how does it work? 

Here, we are going to be explaining everything you need to know about deck bridging.

This way, you can check out the guide below and have all the information you need, including what deck bridging is, how it works, what materials you need to use, and how to do it yourself.

So, if you want to learn more about deck bridging, check out the information below! 

What Is Deck Bridging?

Deck bridging is a technique used to support your deck’s frame and joists before you start installing the deck boards.

It often gets confused with another support-providing technique known by a different name – deck blocking. 

Deck bridging and blocking are often used interchangeably, but when you get down to the finer details, they actually refer to two different things.

Deck blocking specifically attaches wooden blocks to the deck frame’s rim joist and drop beam (if your deck uses a drop beam).

Bridging, on the other hand, is when the blocks are attached to all the inner joists on all sides. They literally build a ‘bridge’ of some sort across your deck by connecting all the inner joists together. 

To others, it’s all the same thing: attaching small blocks of lumber to all of your joists to help provide additional support to the substructure of your deck. 

This is why it is often required by code if your deck’s joists are greater than certain dimensions. Often as little as 8 feet.

Both for decks with drop or flush beams, the addition of deck blocking and bridging will improve its stability and strength.

So, building a deck right will require you to know what bridging is and how to do it. 

The Advantages Of Deck Bridging

The whole point of deck bridging or blocking is to provide support and stability to your deck – but how? 

A deck built without blocking or bridging, you will feel more wobbly when you walk on it.

This is because the individual joists underneath are prone to swaying, buckling, or wobbly as your weight goes from one joist to another.

Making the deck feel unsteady and unsafe to use. 

So, the main purpose and advantage of deck bridging is stability, with the deck being more rigid underfoot.

However, this is not the only benefit of adding bridging or blocking to your deck. Other advantages include: 

• It helps strengthen your deck overall, decreasing warping of joists. 
• Increases the deck’s rigidity deck when faced with high winds and adverse weather, improving its durability. 
• It helps evenly distribute any weight and pressure your joists are under, reducing the chances of total deck failure. 
• It can often be done using scraps of wood and lumber left over from building the rest of your deck’s substructure, reducing waste and cost!  

So, deck blocking and bridging are vital if you want a durable and functional deck! 

What Are The Disadvantages Of Deck Bridging?

There will be a few drawbacks to deck bridging. 

One is increased costs and time to build your deck.

With every bridge blocking needing to be cut and then screwed or nailed into place. This can, at times, require additional lumber to be purchased.

Some people also find deck bridging to be a repetitive, tedious task. Especially when you are so close to getting the decking on and enjoying your new deck.

It makes it frustrating having to install what feels like the same piece of blocking over and over again – but the advantages are definitely worth it! 

If installed correctly, flush or a little low with the joist, this is not a problem but bridge blocking installed incorrectly can cause waves in your decking. Especially with composite decking. If the blocks are a little proud of the joists, the additional height will create bumps in the decking. Making sweeping roughing and overall just an ugly-looking deck. Always take your time to make sure the blocks are not installed high.

Top disadvantages of deck bridging: 

• It requires additional fasteners and lumber, increasing the cost of building your deck. 
• It’s also a very tedious and repetitive task which many people find boring and frustrating. 
• Incorrectly installed causes waves in the decking

Despite these disadvantages, I would never recommend that you skip out on bridging your deck joist. In most regions, it’s legally required, and it improves the quality and durability of your deck! 

How To Bridge Your Deck Joists

Deck bridging, or blocking, is all about taking small blocks of wood and using them to bridge together your joists and the drop beam below them.

Here’s a guide to how to install your blocking and what material and tools you will need.

What You Will Need

Materials:

• Ideally, blocks will be the same material and dimension as your joists. But you can also you slightly smaller blocks, 2″ less than the joist. Saving money on material or allowing for under deck drainage system 
• Galvanized nails or structural screws. 
• Hurricane ties for fastening your blocking to beams (In Some Regions)

Tools: 

• A circular saw to cut your blocks into shape. 
• A cordless drill. Corded drills are much more awkward to use in between each bay, so a cordless drill is definitely highly recommended. 
• Measuring tape for measuring where your deck bridges will go. 
• Speed square for ensuring your blocking is set straight. 
• Chalk line for marking where the bridging goes on the joists

How To Bridge Your Deck Joists

First, you need to take your deck wood and start cutting your blocking. You can do this using any leftover material from your joists or purchase more treated wood as required.

The number of blocks matches the amount of bays between the joists.

Each row of blocking should be equally spaced either by 4 feet or 6 feet apart. Roughy, either half or a third of the joist length. Or for extra strength quarters, but in most cases, that is overkill.

Measure and mark where each bridge should be across your joist. Then snap a line across the deck with the chalk line.

If you have drop beams running underneath your joists, then you can line up your blocking with these beams. In some regions, particularly earthquake zones, these additional blocks will be required.

Regardless of where you install the bridge blocking, either cut the theoretical length (14 1/2 for 16″ on centre joists spacing or slightly smaller). Or measure where the joists are fastened (Ledger or beam) an cut to this length. This will help to straighten the joists as you install the bridge blocks.

Slide each one into place and using your speed square to ensure they are set perfectly straight. Make sure that each end is flush with the joists (and drop beam, if your deck has them). 

Now, you can start attaching your blocking. Either nailing with an air spiker or screw with an impact driver. Screws will reduce squeaking while increasing strength, but nailing is faster.

Where blocks need to be attached to beams and rim joists, you should use hurricane ties and appropriate screws to fasten them securely.

For the inner joists, you can simply use two screws or three nails in each block on either end – unless there is a drop beam running underneath.

In this case, a fastener will be necessary to attach the blocking to the beam as well as both joists. 

Each block should be placed in a staggered pattern or a zig-zag across the entire width of the deck.

This pattern provides the optimal amount of support for your deck boards, while making it much easier to install the blocks.

Installing the blocking in a straight line, you will have to angle your screws or nails to connect the blocking with the previous joist. Reducing stregnth while increasing difficulty installing.

Staggering the blocking makes it much easier to connect each block with both joists on either side. 

Once all your blocks are firmly installed, then congratulations – you will have successfully completed your deck bridging! 

Final Thoughts

And that’s everything you need to know about deck bridging! 

In this guide, we have covered what deck bridging is, the pros and cons of adding it to your decking, and we have provided you with a quick step-by-step guide with all the materials you need.

We hope you have found all this information useful!