Building code requirements for exterior decking railing, guards, and stairs are especially stringent because decks fall into the category of critical health and safety matters. Code requirements for bathroom fans or drywall, while important, rarely touch upon life and death matters. By contrast, deck code is truly a matter of life and death and serious injuries. In a four year study, the Consumer Product Safety Commission found that close to 179,000 people were injured on decks and porches, with over 11 percent of those injuries being the result of structural failure or collapse.
It pays to keep on top of the deck code because the code is continually changing. High-profile deck collapses that result in fatalities typically prompt calls for a fresh look at decking code. For example, your older deck may have toe-nailed connections. If so, be advised that toe-nailing is no longer an accepted connection, according to the current International Building Code (IBC), though older decks may be grandfathered in. As a model code, the IBC is developed by the International Code Council for states, cities, and other local groups to both adopt and adapt for their use. As a result, your locality may adapt the IBC to suit the needs of its citizens. So, be sure to speak to your local permitting office and consult your applicable code before building.
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Deck Railing Height
The minimum deck railing height is 36 inches above the residential deck level. Since this is only a minimum required height for residential structures, higher guards are acceptable. Commercial deck guards, such as those found at restaurants, bars, and at multifamily homes such as apartments or condos, are required to be 42 inches high, minimum.
When Is Deck Railing Not Needed?
Some decks are not required to have guardrails, as long as those decks are 30 inches above grade or lower. If you see a deck that has no guardrails (also called a low-rise deck), this might be the reason: its height remains below 30 inches.
If you decide to construct a guard on a deck low enough that it doesn't require guards, it is up to you as to guardrail height and baluster spacing. However, these guards still must be as strong as guards located on higher decks. It is understood that people will lean against guards, and code requires that these guards not collapse, even though only minor injuries would result.
Voluntary Installation of Low-Rise Deck Rails
Even with very short low-rise decks, many homeowners still opt to construct guardrails. While a 12-inch drop will rarely prove to be fatal to a healthy adult or child or result in serious injury, it still can twist an ankle or injure a lower back.
Changing the context changes the necessity for hand railing. Given that even short-distance falls may lead to chronic pain, serious injury, and even death for elderly people, adding hand railing to a low-rise deck then seems all the more important. Disabled people, too, can benefit from having hand railing on low-rise decks.
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Deck Stairs: Rail Height, Stair Treads, and Weight Capacity
Stair rails for decking should be between 34 inches and 38 inches high. This is measured vertically from the nose of the tread to the top of the rail.
Treads must be at least 10 inches deep, measuring from front to back. The rise, or the vertical distance from one tread to the next, can be no more than 7 1/4 inches high.
Stair treads must sustain a weight of at least 300 pounds in an area no more than four inches square.
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Deck Balusters and Benches
Deck balusters: Balusters are required to be four inches apart or less. One classic rule of thumb: a four-inch diameter ball should barely be able to fit between the balusters. The reasoning is that this four-inch space is the average diameter of a baby's head. Because small children are tempted to stick their heads between balusters and get their heads lodged in place, the four-inch rule is designed to prevent this from happening.
Deck benches: Many homeowners are concerned about preserving the view from their decks and they wonder if benches are acceptable substitutes for deck guards. Unfortunately, benches are not a deck guard alternative. Guards must be installed behind benches, though they do not have to be higher than other guards on the deck.
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Guardrails and Baluster Infill: Minimum Strength
Guardrail strength requirements: The International Building Code mandates that, at a bare minimum, guards must be able to sustain a 200-pound force. In other words, imagine a strong person pushing horizontally against the railing. The railing must be able to sustain 200 pounds of force. However, it is important to note that, from a testing standpoint, the guardrail must sustain 2.5 times the minimum force. In essence, the guardrail must be able to sustain 500 pounds of force.
Baluster strength requirements: Balusters and in-fill rails must sustain a minimum of 50 pounds or a minimum testing force of 125 pounds.