760 mm (30 in.) for those on the freeboard deck; and
450 mm (17.5 in.) for those on the superstructure deck.
The height is to be measured from the deck to the point where water may have access below. Where these heights may interfere with the working of the vessel, a lower height may be accepted, provided ABS is satisfied that the closing arrangements and other circumstances justify a lower height.
The wall thicknesses of vent pipes where exposed to the weather are to be not less than that specified below. For vent pipes located on the fore deck, as defined in 3-2-17/9.7.1, the strength and wall thickness requirements are to also comply with 3-2-17/9.7.2 and 3-2-17/9.7.3: