Building code requirements for exterior decking railing, guards, and stairs are stringent because matters of falling and collapse are at hand.
On top of that, deck code is continually changing. For example, your deck may have toe-nailed connections. If so, be advised that toe-nailing is no longer an accepted connection, per current IBC (though older decks may be grandfathered in).
This building code cheatsheet is derived from the most recent International Building Code (IBC). As a model code,... the IBC is developed by the International Code Council, for states, cities, and other local groups to adapt for their own use. Often, they change the IBC to suit their own needs. So, be sure to consult your own locality's code before building.
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Railing: Railing protects stairs; it runs on the incline up and down the stairs.
Guards: A guard runs horizontally along a landing or other flat area with a drop on the other side.
Balusters: Vertical posts that prevent people (particularly children) from falling off the deck under the railing.
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Minimum Weight Capacity For Stair TreadsStair treads must sustain a weight of at least 300 pounds in an area no more than 4 inches square.
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Minimum Height of Deck That Requires Guards
30 inches above grade. Grade refers to the ground level directly adjoining the deck.
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Can You Construct Any Kind of Guard on Decks Lower Than 36" High?
Yes and no. 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 guard rail height and baluster spacing.
However, these guards still must be as strong as guards located higher on 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.Continue to 5 of 14 below.
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Can a Bench on the Deck Serve as a Guard?No. Many homeowners are concerned about preserving the view from their decks, and they wonder if benches are acceptable substitutes for deck guards; they are not. Guards must be installed behind benches, though they do not have to be higher than other guards on the deck.
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Do Deck Guards Need Balusters?
Yes. Balusters are required.
Alternatively, you can install in-fill guards. These are horizontal guards that parallel the topmost guard.
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Maximum Spacing For Deck Balusters
Four (4) inches or less.
One classic rule of thumb: a 4-inch diameter ball should barely be able to fit between the balusters. The reasoning is that 4 inches is the average diameter of a baby's head. Because small children are tempted to stick their heads between balusters (and get them lodged in place), the "four inch rule" should prevent this from happening.
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Minimum Tread and Maximum Rise For Deck StairsTread is the flat part that you place your foot on. Rise is the vertical distance from one stair to another.
Treads must be at least 10 inches, measuring from front to back. The rise can be no more than 7.25" high.Continue to 9 of 14 below.
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Minimum Strength Required For Guard Rails and Balusters/Rail InfillIBC states that, at a bare minimum, guards must be able to sustain a 200 lb. force. In other words, imagine a strong man pushing horizontally against the railing. The railing has to sustain 200 pounds of force.
However, it is important to note that, from a testing standpoint, the guardrail must sustain 2.5x the minimum force. So, really the guardrail must be able to sustain 500 pounds of force.
Balusters and in-fill rails must sustain a minimum of 50 pounds, or a minimum testing force of 125 pounds.
Short story: 500 pounds for guardrails, 125 pounds for balusters/infill rails.
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Optimal Spacing For Guard Rail PostsThis depends on the type of materials you are using. But generally, 6' is the maximum post spacing to allow guard rails to sustain the force mentioned above.
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Maximum Distance You Can Cantilever a DeckTime was, you could cantilever (extend outward with no vertical supports below) 1/3rd the length of the beam. Now, generally 24 inches in the maximum length.
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Optimal Height For Stair RailsBetween 34" to 38" high, measuring vertically from the nose of the tread to the top of the rail.Continue to 13 of 14 below.
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Minimum Height For Deck Rail Guards36 inches above deck level. Please note that this is minimum required height, and higher guards are better. For example, commercial deck guards (at restaurants, bars, multifamily homes such as apartments or condos, etc.) are required to be 42 inches high.
Sometimes, for residential decks, you may find contractors "nudging" the guard a bit higher (say, to 36.5" or 37") to ensure that the total height does not in some way end up lower than 36", resulting in costly repairs.
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Can a Bench Serve as Balusters or In-Fill Railing?No. The bench can rest against the balusters/railing, but they cannot substitute for them.