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Anatomy of a Deck

Updated: Apr 15

There are several components to a deck but it can mainly be subdivided into two different sections, one being a substructure and the other being a deck surface. Each part of the deck plays a very vital role in the structural integrity of your deck as well as the overall aesthetics of the deck.

Anatomy of a Deck

The substructure is composed of the following individual parts

  1. Footings

  2. Support posts

  3. Beams

  4. Bridging / Blocking

  5. Joists

  6. Hardware

  7. Ledger board

  8. Flashing

Whereas your deck surface is made up of 4 main parts:

  1. Decking

  2. Railing Posts

  3. Railing

  4. Stairs

Substructure

The substructure is the framework that lies underneath your deck board. It is the actual structural support for the deck and provides it with much-needed strength to make it safe and secure. Your substructure and its shape and size very obviously depend on the type of deck that you have. Different deck layouts will require variations in the substructure construction.


These are usually constructed of traditional wood, which is very vulnerable to moisture damage and weathering meaning special treatment and routine check-ups of the structure are needed. This included not only the substructure surface but all the 8 parts that are mentioned below.


Footings

These provide a solid foundation to help spread a load of your deck over a greater surface area. Usually, the best type of footing is a concrete pillar that is poured into a hole you dig in the ground. In colder climates, the bottom of your footings will need to be extended well below the frost line, which varies across different areas, to prevent the footing from shifting as the ground would freeze and thaw, make sure you do some research and testing to figure out what the frost line in your area is.


Support Posts

As their name suggests, support posts quite literally support the frame of your deck. These are directly attached to the footings with metal brackets and sit above the ground. If your deck is taller than 8 feet then your deck may require bracing to keep it from buckling under the load. You should also consult your local building code to make sure you're adhering to the safety regulations.


Beams

A deck component that supports the deck frame. Also called girders. Supporting the frame of a deck are beams installed along with the joists or sometimes between the joists. It is possible to install more beams intermittently in larger decks for extra support.


Blocking

It is also sometimes called bridging and refers to the small blocks of wood installed in between the joists. Blocking is very essential for the anatomy of the deck as it prevents twisting or movement of the joists over time.


Blocking should be installed about every 4’ to 6’ in between joists. Always make sure that the joist and its relevant blocking are level and in a plane across the top of it.


Read more: Decks vs Patios


Joists

Joists are the most prominent part of your deck, as a matter of fact, if you're reading about decks you are going to come across that word the most. Joists are simply installed between beams and are typically spaced at 16” on the center, but these can be spaced at 12” for a sturdier foot feel. Remember that the number of joists is very directly proportional to the size and shape of your deck and how these deck boards can be arranged on the surface. Some more intricate patterns such as herringbone would require very specific joist spacing and blocking to support the intricate pattern.


Hardware

Hardware is as important to the anatomy of a deck as the boards that make up the frame are. These include nails, nuts bolts and other assorted items that hold your board in place.


Ledger Board

This is basically a piece of wood that anchors your deck to the house making it an essential part of the anatomy of the deck. Over time, potential issues such as rot in the ledger board or loose fasteners can cause your deck to pull away from your home, putting its structural integrity at risk.


Flashing

This is often made of L-shaped sheets of stainless steel or vinyl that fit over the ledger to cover the gap between the ledger board and your home. Flashing not only helps protect the ledger board but also channels all water and moisture away from home. For extra protection against any kind of water damage be sure to use flashing tape on top of your ledger board as well as your joists.


Deck Surface Components


These are the most visible parts of your build that you can pretty much customize to your own taste. As a matter of fact, this is what gives your deck the look that you want and you can create anything out of this. One of the most well-known and prominent components is decking.


Decking

This refers to your deck boards, this is essentially what breathes life into your deck. There are several different materials that you can use for decking, ranging from wooden deck tiles to stone deck tiles and composite decking. You need to find the one that suits you well and serves the purpose better but also lasts a long time.


For example, stone deck tiles can quite literally last an entire lifetime without degrading in any shape or form meaning these are pretty much install and forget tiles. Afterward, the only thing you need to take care of is the substructure.


Railing Posts

These are typically made of 4” x 4” wooden posts that are securely fastened to the frame of the deck surface, depending on the best installation practices. Depending on the aesthetic that you are going for these can be covered by decorative composite post sleeves that give it a proper neat and clean finish and help prevent moisture damage.


Railing

A railing system is basically usually made of the top rail, bottom rail, infill which are all installed in between the posts. There are several different types of railing packages available too meaning you can customize the look of your deck by creating a unique railing perimeter.


Stairs

These help you get from the lawn or the patio to the deck itself and are a very important decorative and functional piece of your deck. There are several different types of prefabricated stair packages available too that are easy to install but you can have one custom made too to give it a flavor of your own.