Your deck is 14” off the ground. You know it does not need a guard (barrier railing in lay terms). A guard is only required when the deck gets to be more than 30 from grade (plus some other rules that we are not going into right now).
The point is that you feel you want one anyway–after all, a fall from 14 inches in the dark with a beer in one hand and a girl in the other could still be at best embarrassing.
So you install a nice guard around the decks as you can see in the following pictures.
The problem is that once a guard is installed, even though it is not required, it must conform to the current requirements of a guard. The guard is not merely a thing installed to keep you from falling 30 inches. If that was the case, the spacing between the balusters or rails would not have to be so close together. The spacing is such that a small child will not either fall through or strangle themselves in the openings.
So even though this guard was not required the spacings between the rails on the one deck and the balusters on the other should be no greater than 4” per current standards.
Charles Buell, Real Estate Transactions in Seattle