Q For a long boardwalk that extends to a dock, how do you determine when guards are required?

AGlenn Mathewson responds: Code officials encounter questions such as this frequently. Essentially, you're asking, when is a dock a deck? That's much like asking, when is an office a bedroom?

In most cases, the answer depends on the intended use, which is the decision of the designer. For example, plans for a basement finish often will have a room labeled as a sewing room or an exercise room. Even though it could function as a bedroom, it's not designed as such; therefore, it would be beyond my authority to mandate features - like egress windows, smoke alarms, and CO alarms - required for a bedroom.

Getting back to the question, I'd first look at the boardwalk's intended use. Though a deck and a dock can be nearly identical, one is meant for barbecues and the other for parking a boat. If the boardwalk out to the dock is used just to dock boats, then surrounding it with guards kind of defeats its purpose and makes about as much sense as a guard at the end of a diving board. If it's not meant for parking boats but is actually a walking surface to get from the land to the dock, then it should probably have guards, assuming it's 30 inches or more above the grade or water.

For a structure that extends over water and is intended to be used as a deck - with a grill, table, chairs - I think protection from a fall into the water should be required (though it would be tough to get the code to back that up specifically). I might also consider whether the structure is attached to the home. For example, imagine an actual dock. There's usually no house in that picture, just a narrow boardwalk floating on the water - that's not a deck. Now imagine a house adjacent to the water with a big deck that extends out and over the water - that's not a dock.

That's the approach I'd use were I in the regulatory position, but your local inspector may have a different view.

The use of the dock or a deck must be labeled on the plans. If it is a dock, then I expect the user to be aware of the fall hazard associated with water-related activities and to be focused on the water at the edge. If someone falls off the dock while getting off her boat, that's an accident, but it's part of boating. If someone were grilling and eating dinner on his dock as if it were a deck, he'd be misusing his dock and he'd have to live with the consequences. If his lawyer then came banging on my city's door after an accident, the plans would clearly show that the structure was described as a dock, intended for tying off boats, not for hosting parties.

In administering code, I aim to allow people to decide what the needs and uses are of the spaces they're creating, and then expect them to use the spaces accordingly. The code is intended to mitigate hazards associated with the probable, not the possible.

Glenn Mathewson is a code official in Westminster, Colo., and the technical advisor to NADRA.