Guide: All About Deck Blocking and Bridging

Deck blocking and bridging are some of the strategies that are used in ensuring that the whole structure of the deck is enhanced. Blocking simply involves putting on short members of wood between the joists to offer support and to minimize the sideways movement. Bridging, on the other hand, is created by putting in sets of diagonals to stop joists twisting.

Deck Blocking and Bridging


Deck Blocking (and Bridging)

1. Purpose of Blocking and Bridging

The primary purpose of blocking and bridging is to:

  • Ensure all loads are well distributed or spread out on the deck.
  • Timber Joist: Protect it against twisting or cupping off over time.
  • Increase the overall strength of the deck structure.
  • Obey with the law of building construction and safety regulations.

These factors mean that if appropriate blocking is lacking, the deck can experience swaying and instability that is dangerous and shortens the material’s life. Blocking and bridging help to transfer the weight and stress over the entire structure of the deck which is important for its stable functioning in the long term.

2. Types of Blocking and Bridging

Solid Blocking:

This is the most common of all the types and entails inserting pieces of lumber in the form of solid and enclosing them within the space between joists. Solid blocking is easy to spot and gives a lot of backing.

Cross Bridging:

This type involves the use of wood blocks or metal pieces with all the pieces installed at a right angle to the joists. Cross bridging assists in providing additional support to the joists and prevent them from turning or twisting.

Metal Bridging:

Metal bridging involves the use of steel or galvanized metal pieces to span the gap in between the joists. Metal bridging is long-lasting and can resist the vagaries of weather conditions.

All of them are useful and can be generally chosen according to what you need and what conditions your deck has.

Deck Blocking and Bridging


Deck Block Spacing and Requirements

The most important aspect for those wanting to put up a deck is the right spacing of the deck blocks. The spacing requirements may also change based on several factors such as the type of wood to be used, the size of the joists and other regulations that may apply under the law in a certain region. However, a general guideline can be followed that blocks should be placed in such a manner that the distance between them should not exceed 8 feet.

1. Factors Influencing Spacing

Several factors influence the spacing of deck blocks:

Joist Span:

It refers to the space between the supports of the joists. Long spans usually call for more blocking than shorter spans, depending on the durability of the wooden spans.

Deck Load:

The expected force applied on the deck through furniture, people or any other load that will be placed on the deck. Higher loads require blocking at shorter intervals.

Wood Species:

There are differences in the strength and elasticity forces in the various species of woods. For instance, what may be recommended for use on the softwood may not necessarily be the same as that required to be used on the hardwood.

Deck Usage:

A deck that is intended to be utilized intensively and by many individuals may require sturdier blocking.

2. Building Codes

Local building codes should be considered because they offer the necessary guidelines regarding deck block spacing. These codes aim to make sure that the deck is not only safe and strong, but also compliant with the legal requirements of the future to prevent any legal troubles and dangerous structural flaws. Building codes typically specify:

  • Maximum joist spacing.
  • Required blocking intervals.
  • Minimum lumber dimensions.
  • Admissible categories of blocking materials.

Therefore, It is important to understand that operating within these codes is not just a ‘rule that must be followed’ but a practice that will help you produce a safe and long lasting deck.

Common Standards:

  • In case of joists with 16 inches OC, blocking should be provided at the intervals of 7 to 8 feet.
  • If the joists are spaced at a 24 inch on center, blocking should be installed every 4 to 6 feet.

Deck Blocking and Bridging


Ways to Connect Deck Joists with Blocking

1. Nailing and Screwing

One of the traditional ways of fastening the deck joists to blocking is through nail or screws fixation. This method is straightforward and effective:


Less time consuming to install than screws but they may not exert as much force as screws are capable of. Various types of nails can be even more vulnerable to becoming loose as the wood expands and contracts.


Have a better protection and do not tend to become less tight in the future. Screws are preferred for their capacity to hold into the material and their capacity to sustain withdrawal loads.

2. Joist Hangers

Joist hangers are metal which are mainly used to offer a firm connection between joists and blocking. They are useful when constructing wider decks or when extra support is required such as for the construction of larger decks. Joist hangers make it possible to hold the blocking firmly and this helps in making the structure strong and firm. When using joist hangers:

  • Make sure the hangers are compatible with the size of joists you are going to install.
  • Have the hangers made of galvanized or stainless steel to avoid rusting of the metal.
  • Secure hangers properly with suitable nails or screws meant to secure hangers properly.

3. Toe Nailing

Toe nailing is done by placing nails in a slanting position under the joist and through the blocking. This technique is efficient in ensuring blocking in restricted areas where it may be difficult to apply straight nailing or affiliate screws. This offers considerable strength but risks splitting the wood; it is best used when the leverage for maximum pressure is low.

4. Adhesives and Fasteners

Sometimes, construction adhesives may be combined with nails and screws to increase the force bearing characteristic of the joint. If the blocking is installed with some gap then it is better to apply a bead of adhesive on the ends of the blocking before fixing it so that it can reduce movement and noise.

5. Double Blocking

Double blocking is provided by arranging two blocks one besides the other and locating them in between two joists. This one is employed for extra strength and stability, mostly in regions of higher loads and stress. It may also be applied on the ends of joists to have a flush nailing to the deck boards.

Deck Blocking and Bridging


Deck Joist Blocking Methods

1. In-line Blocking

In-line blocking is blocking the blocks running directly across the joists. This method offers a smooth finish to the deck, and is appropriate for decks that have to be smooth and uniform in their appearance. This method also favors the alignment and securing of the blocks in the work piece.

Advantages Disadvantages
  • ·Simple installation
  • Clean and uniform appearance
  • Easy to align
  • May not be as laterally stable as staggering or herringbone blocking

2. Staggered Blocking

Staggered blocking is a placement of blocks – some of them will be placed between the joists while others won’t. Assist to reduce the chances of joists splitting and gives better flank to the structure which is better in load bearing. Staggered blocking is mainly carried out to load regions where the deck experiences a number of loads.

Advantages Disadvantages
  • Increased lateral stability
  • Minimized joist splitting risk
  • Distributes loads more evenly
  • More complex installation
  • Requires accurate measurements in addition to getting the right angles.

3. Herringbone Blocking

The other one is herringbone blocking which is a little more stylistically appealing as patterns for the blocks are installed in a crossing manner. This method offers quite good lateral support and gives a necessary esthetic look to the deck. In fact, herringbone blocking is quite beneficial for decks that have to load bear and also beautify the surrounding area.

Advantages Disadvantages
  • Superior lateral support
  • Aesthetic appeal
  • Effective load distribution
  • Most complex to install
  • Demands accurate cutting and joining

4. Diagonal Blocking

Diagonal blocking is similar to herringbone but less complex; the blocks are aligned in a diagonal direction intersecting the joists. This method improves lateral stability and is more straightforward as compared to the herringbone installation.

Advantages Disadvantages
  • Improved lateral stability
  • Its installation is easier compared to that of herringbone.
  • Provides a decorative touch
  • Needs precise slicing and shaping
  • More complex compared to inline and staggered blocking

Deck Blocking and Bridging


How to Install Deck Blocking

1. Measure and Mark

If the joists are spaced evenly, begin to measure the distance between two adjacent joists, and this is where the blocking will be required. Make sure that the marks are in line with another and that the distances in-between are approximately equal.

2. Cut the Blocking

Carry the blocking pieces to the work area and cut them to fit nicely in between the joists in the floor. This proved that the length of the blocking should depend on the intervals between the joists.

3. Position the Blocking

Lay the blocking between the joists according to the marked positions previously indicated. Make sure that the blocks are lying flat and parallel to the upper cross-section of the joists.

4. Secure the Blocking

To fix the blocking ensure that you use nails screws or even joist hangers depending on the attached area. Also, when using nails or screws, recommend that they are placed at an angle for maximum grip.

5. Check Alignment

After all the blocking is in, make sure everything lined up and evenly spaced and also all the blocking is tight. If necessary, modify any of the blocks.

6. Final Inspection

Check all the blocking to verify that the first course was set up correctly, and all is tightly interlocked. This step is important in order to avoid movement and instability of the deck.

Deck Blocking and Bridging



1. Why is deck blocking necessary?

A: Deck blocking is required to stop joists from twirling, improve the strength of the deck, and distribute loads on them. It also assists in following the code requirements and the structural stability of the deck that is to be established.

2. Can I use any type of wood for blocking?

A: Different types of woods can be used for blocking but it is recommended to use wood of the same type used for the joists in order to avoid expansion difference problem. The most popular type of wood is the pressure-treated wood due to its hardness and ability to resist moisture and pests.

3. How often should I inspect the blocking on my deck?

A: House inspections are suggested to be carried out in a usual manner, at least once a year. Examine the blocks for any signs of movement, having loose screws or nails or any form of damage. Doing maintenance frequently assists in rectifying problems before they become severe.

Update cookies preferences
Scroll to Top