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10 Best Things You Need To Know About Deck Blocking

When building a deck, there are many things you need to take into account to ensure its strength and durability. One of the most important aspects of deck construction is joist blocking. Joist blocking helps keep your deck framing straight and strong and can also help to prevent twisting and to sag over time. In this blog post, we will discuss the importance of joist blocking and how to install them properly.
man measuring deck frame

1. What is deck blocking?

Deck blocking is a piece of lumber installed perpendicular to the deck joist blocking. Its primary purpose is to support the deck joists and help prevent them from twisting or bending. Blocking is typically made from the same material as the deck project, and it is installed every 16 inches along the deck joist span.

2. Why is deck blocking important?

There are several reasons why deck blocks are essential:
If you’re planning on building a deck, be sure to include deck blocking in your plans. It’s an essential part of creating a strong, durable deck that will last for years.

3. Benefits of deck blocking

Deck blocking is a technique used in deck construction to support the deck joists. This is done by installing wood blocks between the deck joists and the decking. Deck blocking provides several benefits, including:

4. When is deck blocking necessary?

There are a few circumstances when blocking is necessary. The most commonn instance is when the deck joists are not sized correctly for the span. In this case, blocking can add strength to the deck.

Blocking is also necessary when installing decking over a roof, as it provides extra support for the deck joists. Finally, deck blocking may be required by local building codes.

If you’re unsure whether or not your deck needs blocking, it’s always best to consult with a professional deck builder. They will be able to assess your deck and determine if blocking is necessary.

Building a deck without blocking can result in a weaker outdoor space that is more susceptible to damage. In some cases, it can also void your deck warranty. So if you’re planning on building a deck, be sure to include blocking in your plans.


5. The different types of deck blocking

Several different types of deck blocking can be used, depending on the deck’s needs.

Full Depth Solid Blocking:

This is the most common type of deck blocking. It is used when there are no obstructions, such as vents or pipes, in the way. The blocking runs the full depth of the joist and is fastened to both sides.

Half-Depth Blocking:

Half-depth blocking is used when there are obstructions that prevent the use of full-depth blocking. It is fastened to only one side of the joist.

Single Blocking:

Single deck blocking is used for very short joist spans or when there are multiple obstructions. It is fastened to only one side of the rim joist and does not run the full depth.

Unenclosed Blocking:

Unenclosed deck blocking is used to support an overhang or when the deck will be enclosed on three sides. It is not fastened to the joist and does not run the full depth.

End Blocking:

End deck blocking is used to support posts or beams. It is fastened to only one side of the joist and does not run the full depth
Deck blocking is a vital part of deck construction. It strengthens the deck, prevents joist deflection and twisting, and supports point loads. Several different types of deck blocking can be used, depending on the deck’s needs. When selecting deck blocking, be sure to choose a material compatible with the decking and joists.

6. Deck blocking spacing

When deck blocking is not spaced correctly, it can lead to several problems, including deck joist bowing, deck joist twisting, and deck boards cupping. Many deck building codes point out that every deck should meet spacing requirements to create a safe outdoor space. This is why deck builders recommend that deck blocking be spaced every 16 inches in the center. This will create a solid foundation for your deck, preventing common decking problems.
deck blocking

7. How to make sure you have the proper deck joist spacing?

You should check two sets of standards when planning your deck frame – your deck material’s standards and the local building codes.

Joist spacing with composite decking

Consult the manufacturer’s guidelines to ensure that you are using the appropriate joist spacing for your decking material. Every deck board manufacturer puts its decking material through in-depth independent testing to find the proper joist spacing. This ensures that your deck is safe and looks great.

Local building codes

If you’re unsure about the joist spacing requirements in your area, it’s always best to consult with your local building department. They will be able to tell you the specific spacing requirements for your deck and help you ensure that your deck is up to code.
deck on stones

8. Alternatives to deck blocking

According to NADRA, there are a few alternatives to deck blocking, though they may not be as effective. Some homeowners use metal L-brackets screwed into the framing to attach the deck boards.

Others use a construction adhesive to adhere the deck boards to the joists. While these methods may be less effective than deck blocking, they may be more feasible for some homeowners.

9. How to install blocking?

Now that we covered the basics of deck blocking let’s get into how to install it. You can install blocking by attaching it with nails or screws. For a more permanent connection, use decking screws.

1. Determine the placement of the deck blocking

First, you’ll need to determine the placement of the deck blocking. Deck blocking is typically installed every 16 inches on the center. However, be sure to check your local building codes for the specific requirements in your area.

Once you’ve determined the placement of the deck blocking, mark the location of each block on the joists with a chalk line.

If you’re attaching the deck blocking with screws, predrill each hole with a countersink bit. This will make it easier to drive the screws and prevent the wood from splitting.

2. Cut the deck blocking to size and shape

Next, you’ll need to cut the deck blocking to size. The deck blocking should be about 12 inches long for a standard deck. However, you may need to adjust the length depending on the design of your deck.

Once you’ve cut the deck blocking to size, use a jigsaw to cut each block to shape. If you’re using decking screws, be sure to countersink the holes.

If you’re attaching the deck blocking with nails, use a hammer to drive the nails into the joists. Start at one end of the deck and work your way down.

3. Fasten the deck blocking

You’ll need to fasten the deck blocking to the joists. If you’re using screws, drive two screws into each deck block. If you’re using nails, drive three nails into each deck block. Start at one end of the deck and work your way down. Be sure to check that the deck blocking is level as you go.

4. Install the decking boards over the deck blocking

Start at the outside edge of the deck and work your way in. Use deck screws to attach the deck boards to the blocking. Be sure to predrill all holes to avoid splitting the wood.

It is also a good idea to use washers under the head of each screw. This will help keep the boards from cupping.

When you reach the end of the deck boards, cut them to fit snugly against the deck railing. Use a circular saw to make the cuts.

After installing tall boards, check for any nails that may have popped up and hammer them back down.

10. Tips for a proper deck blocking installation

Installing blocking is critical to the stability of your deck. Here are some tips to ensure that you do it properly:


If you’re in the process of building a deck, it’s essential to make sure that you install your joist blocking correctly. This will help keep your framing straight and strong and prevent twisting and sagging over time.

If you need help with your deck installation, don’t hesitate to contact us. We would be happy to walk you through the installation process and answer any questions you may have.