Every spring kicks off deck building season, when homeowners can’t wait to have a deck party and builders start signing contracts for both rebuilds and new decks. As a building official, I find it’s a time when I refer a lot of folks to the code book.

Knowing the code requirements helps you to do it right up front. In my mind, a deck builder who doesn’t own a copy of the International Residential Code (IRC), even an outdated one, is like a lawyer who doesn’t own a law book. Now, most deck builders don’t need to own a copy of the International Building Code (IBC), which is geared more toward multi-family and commercial construction. But there are times you might find it helpful, say when you get that big job in an apartment or condo complex. Once the building you’re working on houses more than two families, the IBC becomes the governing code — and it’s a real game changer. This article will use the 2003 IRC as a base reference, and contrast it with the 2003 IBC when necessary.

When residential builders transition to multi-family or commercial work, one of the most common mistakes involves railings, which code books refer to as “guards.” Guards are used not only around a raised deck, but also alongside stairs. Guard heights vary between the IRC and the IBC. Single-family homes and two-family dwelling units (code classification R3) share the requirement of minimum 36-inch-high guards anywhere the walking surface is 30 inches or more above the adjacent floor or grade. However, three-family and larger residential properties, as well as motels, hotels, dormitories, apartments, and the like — classified as R2 — require a minimum 42-inch-high guard for the same conditions.

I don’t know how many times I’ve heard the argument, “Yeah, but they’re all residential units!” That doesn’t matter. You need to build to the standards of the code adopted where you live, and most of the country makes a distinction as described above. Every state has passed amendments that alter sections of the code; however, the basic concepts remain the same. I encourage builders to buy the “Commentary” version of the code, which explains things in laymen’s terms.

Guard Heights
Let’s look at sample guard heights for two different scenarios. If you’re building a new deck or restoring an old one in an R3 building, the guards must be at least 36 inches high and the stairs will require a minimum 34-inch-high guard and a graspable handrail (the Stair Manufacturers’ Association provides a good visual explanation of this at stairways.org). For an R2 condo project, however, you must install 42-inch-high guards for both new construction and replacements of existing guards. The guards along the exterior stairs also must be 42 inches high, and a graspable handrail on both sides of the stair is required.
These instances depict standard differences in residential occupancies versus multi-family residences; neither has anything to do with special circumstances, such as restricted spaces, or replacement with “like” materials when historical elements come into play.

Mixed R3 and R2
Sometimes R3 and R2 uses collide. Where I work, it’s fairly common for owners of two-family (R3) dwelling units to add a third or fourth apartment, bringing in significant additional monthly income. In order for them to add the additional dwelling unit(s), there has to be a “change of occupancy” from R3 to R2. On an existing deck, guard rails with the R3 required height of 36 inches won’t need to be changed. But decks for the new unit(s) will look different because their guards will have to be 42 inches high.

That won’t be the only difference. Any new stairs to the R2 decks won’t be allowed to exceed a 7-inch rise and an 11-inch run (in Connecticut, where I work, stairs on the original R3 deck could have an 81⁄4-inch rise and a 9-inch run). And if you rebuild the existing R3 deck, it will then have to comply with R2 requirements.

There may be other requirements as well. You don’t want to have to rebuild something you built in error — it always costs more to do it twice. A mistake could cost the monthly payment for that 4x4 pickup. Why not call your local building inspector first to verify the requirements? Then the additional costs are only those of a simple change in what you order for the project.