Deck railing codes. All decks higher than 30″ above grade must have a guardrail. If you choose to install a guardrail on a deck lower than 30″, you must still meet code requirements. Decks attached to single-family detached homes are regulated under the rules of the International Residential Code (IRC). The IRC requires guardrails to be at least 36″ in height, measured from the deck surface to the top of the rail. Commercial decks attached to multi-family buildings, such as apartment buildings or businesses, are regulated under the International Building Code (IBC). The IBC requires 42″ high guardrails. In either case, you can build taller guardrails as long as they conform to all other requirements stated in the code.
You can use a variety of styles as long as the interior sections of the rail don’t have any openings large enough to pass a 4-inch diameter sphere through. In the case of guardrails for stairs, there is an exception that allows up to a 6” diameter sphere through the triangle opening formed by the stair riser, stair tread and bottom rail. The guardrails must be strong enough to withstand a concentrated 200 lb force anywhere along the top of the rail. To achieve this, you should space rail posts no greater than 6″ apart. The sweep space between the deck surface and the bottom rail must be less than 4″.
For stairs, the code requires handrails to meet the standards specified in R311.5.6.3 of the IRC. Place the top edge of the handrail between 34 inches and 38 inches above the nosing of the stair treads. Return and terminate the handrail ends at the rail posts. The handgrips must allow a minimum of 1-1/2” space between the handrail and the guardrail or wall. A variety of gripping surfaces may be acceptable but must meet requirements for the gripping surface. Flat 2×4 and 2×6 handrails are not acceptable. A circular cross-section of a handrail must have an outside diameter of between 1-1/4” and 2”.
Test engineered railing systems to ensure they meet IRC and IBC building codes. The tests include:
Infill Load Test: Test the strength of the balusters to ensure that a one-square-foot area can resist 125 lbs of force.
Uniform Load Test: The top rail must be able to sustain 125 lbs of force applied horizontally or vertically.
Concentrated Load Test: The top rail must be capable of holding a point load of 200 lbs of force applied to the mid-span, on the side of a post and top of a post.
An accredited third-party testing agency performs these tests.
