Are decking codes different than building codes?


If you're seeking to build a capped composite deck, one of the first things to determine is how local building codes will affect your planning. Codes vary from region to region, depending on factors like climate and demographics, so there is no one-size-fits-all guide to decking regulations. But it's also important to note that building codes and decking codes can overlap in some areas while differing in others.

How do I know which codes govern my deck project?

Before we go any further, it makes sense to address regulation research - without having the proper authority on decking codes, your deck may accidentally end up in a state of violation.

"Never assume that codes from one region will carry over to another."

A good place to start is with the American Wood Council's Prescriptive Residential Deck Construction Guide, which provides a wealth of information on how to build a deck in accordance with regulations from the 2015 International Residential Code. The resource also provides best-practice recommendations separate from strict code adherence. While the guide is a good source of information, it doesn't replace manufacturer-provided installation instructions.

As for local regulations, the best course of action is to seek information through your state or city website, or even reach out to the state division of building standards and codes. Because of the potential for vast differences in regulations, never assume that codes from one region will automatically carry over to another.

Are any decking codes considered universal?

The 2015 International Residential Code is the closest thing to a universal guide for building codes, including those that apply to decks. A few items do serve as constants that you should keep in mind while planning your deck's layout, like railings, stairs and structural support. Railings alone include several components with specific requirements:

  • Railings: No deck is complete without them. The IRC mandates guardrails to be at least 36 inches high and to allow for firm grasp. On the other hand, the International Building Code calls for 42-inch high guardrails.
  • Balusters: The deck railing supports also must be spaced out such that there isn't a large gap where someone could get stuck or fall through. The 4-inch sphere requirement is a good test - an object of that size should be unable to pass.
  • Bottom rail: For deck railing systems that have support blocks (often a section of baluster) connected to a bottom rail, that bottom rail must be at most 4 inches above the deck surface.

Those are just a few highlights - and only those that apply to railings. Clearly, there are plenty of standards that apply to decks across the board. But while the IRC is the benchmark, many local codes will call for tighter restrictions. In other words, decking codes won't be more relaxed than what is established in the IRC, but they may well be more strict.

Does my building type matter when examining decking codes?

Building shape and size will affect the way you build your deck - not just placement, but the requirements for fastening your deck to the building. However, while building type might not impact the codes, it does matter whether you're dealing with a commercial structure or a residential one. Note that the IRC is specifically intended for residential buildings.

Commercial buildings fall under city or state governance, along with bodies like the U.S. Department of Energy. However, deck don't typically require energy efficiency ratings, so for commercial structures, it's best to defer to local government authority.

Despite the litany of decking codes and overlapping requirements, there's no need to be intimidated. By and large, the codes exist to ensure security and stability - features that should be most important to you, anyway. As you begin your decking project, keep the codes in mind and be sure to consult the guidebook when it comes time to choosing your materials and style.