Anatomy of a Deck

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The anatomy of a deck is made up of two major parts: the deck substrate and the decking surface.

Johnson Lumber has 100 years in the lumber game, and decking is just one of the many project types we have perfected since. Here’s a rundown of what makes a proper deck.

Deck Substructure

The framework beneath your deck boards is referred to as the substructure. This part of the anatomy of a deck provides the structural support required for your deck to be safe and secure. Different deck layouts will necessitate different substructure construction.

Substructure deck components are typically made of traditional wood that is susceptible to moisture damage and weathering. As a result, regular inspections of your substructure – and all of its listed components – should be performed at least once a year.

Here are the parts that make up your deck substructure:

1 | Footings

Footings provide a solid foundation for your deck, distributing the load over a larger surface area. A concrete pillar poured into a hole dug in the ground is typically the best type of footing.

To prevent the concrete from shifting as the ground freezes and thaws in cold climates, the bottom of your footings must extend below the frost line, which varies by region.

2 | Support Posts

Support posts, as the name implies, support the deck’s frame.

They are typically attached with metal brackets to the tops of footings and sit above grade (ground-level).

Decks taller than 8 feet and those built on a slope may necessitate bracing to prevent the support posts from buckling under the heavy load.

3 | Beams

Beams, also known as girders, are deck components that support the deck’s frame. To support the deck’s frame, beams are installed horizontally alongside the rim joists (joists around the perimeter) or below the joists. More beams may be installed intermittently for extra support on larger decks.

4 | Blocking

Blocking, also known as bridging, refers to the small wood blocks installed between the joists for support. Blocking is essential to the anatomy of a deck because it prevents joist twisting or movement over time.

In between joists, blocking should be installed every 4 to 6 feet. Ensure that the joists and blocking are level and are always level across the tops.

5 | Joists

Joists are one of the most visible parts of a deck’s anatomy because they provide structural support for the deck floor.

Joists are installed between beams and are typically spaced 16 inches on center but can be spaced 12 inches for a firmer footing.

The number of joists on your deck will be determined by its size and how the deck boards are arranged on the surface. Deck patterns, such as a herringbone pattern, will, for example, necessitate specific joist spacing and blocking to support the intricate pattern.

6 | Hardware

Hardware is just as important as the boards that make up the frame in the anatomy of a deck.

Joist hangers and screws are examples of hardware pieces that hold your deck components together. The use of the proper fasteners is critical for the structural integrity of your deck.

7 | Ledger Board

The ledger board is a piece of wood that connects the deck to your house, making it an important part of the deck’s anatomy.

Potential issues such as rot in the ledger board or loose fasteners can cause your deck to pull away from your house over time, jeopardizing its structural integrity. Annual deck inspections can help detect problems early on and save you money on a full-fledged deck replacement.

8 | Flashing

Flashing is typically made of L-shaped stainless steel or vinyl sheets that fit over the ledger board to cover the gap between the ledger board and your home.

Flashing not only protects the ledger board, but it also directs water and moisture away from your home. Deck joist flashing tape can be applied to the top of your ledger board as well as your joists to provide additional protection against water damage.

Surface of the Deck

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The deck components of the surface refer to the visible parts of your build, the majority of which can be customized to your liking. When planning your deck’s decking, railing, and stair designs, keep the overall look and feel you want to achieve in mind. All of these elements will work together to create the design — and contribute to the overall feel — of your outdoor living space. This is part of the anatomy of a deck that people will see the most of.

9 | Decking

Decking refers to the deck boards, which are the most visible part of the deck surface’s anatomy. Deck boards are available in a variety of materials, colors, and sizes.

Decking, like your substructure, will require fasteners for a secure installation. Certain deck board profiles (such as grooved boards) may only work with specific fasteners.

10 | Railing Posts

Railing posts are typically made of 4×4 wood posts that are securely fastened to the frame or deck surface, depending on best practices for installation. Wood posts can be covered by decorative composite post sleeves, depending on the style of your deck railing, to give it a clean finish and help prevent moisture damage. You can also choose sleek aluminum posts that are narrower, giving you a more minimalist appearance.

11 | Railings

The top rail, bottom rail, and infill (the section between the top and bottom rails) of a railing system are all installed between the posts. Material options for your rails and infills vary, allowing you to personalize the look of your railing for a distinctive deck perimeter.

Proper installation of your railing is critical because it is a key component of both safety and design.

12 | Stairs

Stairs connect your deck to your lawn or patio. Depending on the height of your deck, you may have one to two steps or a full flight of stairs. Deck height and shape are important considerations in deck stair design, which can range from straight stairs to wrap-around stairs and more.

Johnson Lumber is Your Decking Expert

Just knowing the anatomy of a deck isn’t enough! Get one installed today!

Don’t wait for the spring to install your new outdoor deck. Get in touch now and let’s get going on your project. We’ll have your deck planned and installed in time for your next BBQ.

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