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code requirements for decks :: large cedar deck on a hillside

Each city in the U.S. has requirements about the structures you can build on your property. In some areas, you can’t even dream about a deck, for example, until you’ve obtained a permit. While getting a permit for a simple wood deck can seem like a hassle, the building codes attached to them ensure the safety of your family and reduce your personal liability risks.

Although specific residential building codes vary from city to city, the following is a look at the common code requirements for decks in most municipalities.

Common Decking Codes

Basic requirements:

The International Residential Code (IRC 2018) specifies that decking material must be made of dimensional lumber with a 2-inch nominal thickness. Each decking segment must bear on at least four joists.

Deck Framing Plan:

When you present your deck framing plan to the city planner, you’ll need to show the joist and beam layout of the structure, including the location and size of the footings, ledger boards and posts.

Post Requirements:

Use posts made of 6×6-inch (nominal) lumber or larger. The maximum height of posts at 6×6 is 14 feet, and you should center the posts on the footings.

Footing Requirements:

Install footings on solid ground and at least 12 inches below undisturbed ground or the frost line, whichever is deeper. If a deck footing is 5 feet or closer to the exterior of your home, the deck’s footing must be at the same elevation as footing used for the home’s foundation.

Does My Project Need a Building Permit? :: Building Permit Requirements & Why They’re Important

Stair Requirements:

Use a minimum of 2×12-inch lumber for the stair stringers. As you build the stairs, make the treads at least 10 inches deep and 36 inches wide. Make the stair risers 7.75 inches high or shorter. If the total rise of the staircase is 30 inches or more, you need to install a stair guard and handrail that’s at least 34 inches from the nosing of each step.

code requirements for decks :: large wood deck overlooking water

Common Deck Code Violations

* Failing to Protect against Decay

Depending on where you live, even if you use preservative-treated lumber, you may need to coat the cut ends of wood with an additional treatment.

* Using the Wrong Fasteners or Not Enough

Using incorrect or insufficient fasteners poses a significant safety risk. Proper fasteners are made of stainless steel, copper, silicone bronze or hot-dipped zinc-coated galvanized steel.

More: For more on selecting the right fastener for a deck job, our feature on maker resources from Simpson Strong-Tie.

* Using Non-Approved Materials

Use 2×4 or 2×12 lumber for the structural beams and girders of wood decking. You can also get cited for not spacing the materials properly.

* Poor Anchoring and Support

The construction of your deck must prevent uplift and racking so it doesn’t become a projectile if there’s an earthquake or high winds.

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Deck Codes are constantly changing. For the latest, refer to American Wood Council’s Prescriptive Wood Deck Guide (aka DCA6). For a complete list of requirement regarding the construction of a deck, talk to your city planner or building inspector. This individual can prove a valuable resource to help ensure your deck is safe and strong.

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— Dave Nichols writes Rick’s Custom Fencing & Decking. Rick’s Fencing provides materials, design, service and installation of cedar decks in the Pacific North West. For all contributions from Rick’s Fencing and Decking, please see their Author’s page, here. For more in our Decking category – the link there. ~jb

All images via Rick’s Custom Fencing and Decking.