All decks greater 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 multifamily buildings, such as apartment buildings or businesses, are regulated under the Internation Building Code (IBC). The IBC requires 42″ high guardrails. In either case, you are allowed to build taller guardrails as long as they conform to all other requirements stated in the code. Most building departments in Canada require 42″ high guardrails.
Measure from the deck floor to the top of the rail between posts. This must be at least 36″ high to meet IRC requirements. Make sure your sweep space and all infill openings will not allow a 4″ sphere to pass through.
Sweep Space Bottom Deck Rails
This popular rail style leaves a 4” space below the bottom rail to allow for snow and debris to be swept off the deck surface. Rail posts are attached to the deck frame and support the infill sections. Rail posts need to be properly fastened and should not be spaced more than about 6 feet apart to prevent a saggy or bouncy rail.
Many builders run a 2×6 top cap continuously over the top of the posts and top rail to provide a clean finished edge and the practical purpose of providing a surface to set glasses, etc. The pickets can be considerably shorter because they don’t need to be individually attached to the deck rim and they are raised off the floor. Most deck builders prefer this rail type for is simplicity and functionality above all others for wood rail construction.