(a) Purpose. This section lists spaces which are exempt from inclusion in tonnage.

(b) Spaces on or above the line of the uppermost complete deck. The following spaces or portions of spaces on or above the line of the uppermost complete deck are exempt if the spaces or portions are reasonable in extent and adapted and used exclusively for the purpose indicated:

(1) Spaces for anchor gear, including capstan, windlass, and chain locker, are exempt.

(2) Companions and booby-hatches protecting stairways or ladderways leading to spaces below are exempt, whether or not the spaces below are exempt.

(3) Galley or other spaces fitted with a range or oven for cooking food to be consumed on board the vessel are exempt.

(4) Spaces designed to provide light or air to propelling machinery are exempt, as follows:

(i) When propelling machinery is located entirely on or above the line of the uppermost complete deck, the entire propelling machinery space and all fuel bunker spaces that are also located above that line are exempt as light or air spaces. (See exception in §69.121(d)(1) for framed-in spaces.)

(ii) When part of the propelling machinery projects above the line of the uppermost complete deck into a space used exclusively to provide light or air to the propelling machinery, the entire space is exempt as light or air space. When any portion of this space is used for purposes other than providing light or air, only the portion of the space used for light or air, the space occupied by the propelling machinery itself, and a propelling machinery working space allowance under §69.121 limited to two feet, if available, on each side of the propelling machinery are exempt.

(iii) Any part of an escape shaft, or a companion sheltering an escape shaft, above the line of the uppermost complete deck is exempt as light or air space.

(iv) Space that would otherwise be exempt as a light or air space is not exempt when propelling machinery is boxed-in and does not extend above the line of the uppermost complete deck. Any portion of the boxed-in space above the line of the uppermost complete deck is exempt.

(5) Skylights affording light or air to a space below, other than to propelling machinery spaces. Space immediately below the line of the deck on which a skylight is located is exempt only when there is an opening in the next lower deck directly below the skylight to permit light or air to an even lower deck.

(6) Machinery spaces, other than for propelling machinery under §169.121.

(7) Spaces for steering gear.

(8) Water closet spaces that are fitted with at least a toilet and are intended for use by more than one person.

(9) The space in a wheelhouse necessary for controlling the vessel.

(c) Passenger spaces.

(1) As used in this section, the term “passenger” includes officers and enlisted men on military vessels who are not assigned ship's duties and not entered on the ship's articles.

(2) As used in this section, “passenger space” means a space reserved exclusively for the use of passengers and includes, but is not limited to, berthing areas, staterooms, bathrooms, toilets, libraries, writing rooms, lounges, dining rooms, saloons, smoking rooms, and recreational rooms. The space need not be part of or adjacent to a berthing area to be considered a passenger space. Spaces used by both passengers and crew members (e.g., first aid stations), or used for passenger support but not accessible to passengers at all times (e.g., vaults on a gaming vessel) cannot be exempted as passenger space.

(3) A passenger space located on, or above the first deck above the uppermost complete deck is exempt from tonnage. To qualify as the first deck above the uppermost complete deck, the deck must be at least six inches above the uppermost complete deck at all points along its length.

(d) Open structures.

(1) Structures that are located on or above the line of the uppermost complete deck that are under cover (sheltered), but open to the weather are exempt from tonnage as open space. The following additional requirements apply:

(i) If a structure is divided into compartments, only those compartments which are open to the weather are exempt from tonnage under the provisions of this section.

(ii) Open space cannot progress vertically through openings in a deck within the structure.

(iii) A space that is outside a structure's boundary bulkhead as defined in §69.53 is considered open to the weather provided the space is eligible to be treated as an excluded space under the provisions of §69.61, regardless of whether or not the space is fitted with means designed for securing cargo or stores.

(2) A structure is considered open to the weather when an exterior end bulkhead of the structure is open and, except as provided in paragraphs (d)(4), (5), and (6) of this section, is not fitted with any means of closing. To be considered open to the weather, the end bulkhead must not have a coaming height of more than two feet in way of any required opening nor any permanent obstruction within two and one-half feet of the opening, it must be fitted with a deck or platform that is a minimum of two and one-half feet wide on the exterior side of the opening, and it must have one of the following:

(i) Two openings, each at least three feet wide and at least four feet high in the clear, one on each side of the centerline of the structure. If the openings lead to two separate interior compartments, there must be circulation of open space between the two compartments via a single such opening, or series of such openings, in the intermediate bulkhead(s).

(ii) One opening at least four feet wide and at least five feet high in the clear.

(iii) One opening at least 20 square feet in the clear with a breadth in excess of four feet and a height of not less than three feet.

(3) A compartment within an open structure is considered open to the weather only when an interior bulkhead of that compartment has an opening or openings that meet the requirements for end bulkheads under paragraphs (d)(2)(i) and (iii) of this section. Other compartments within the structure are not considered open to the weather. The following additional requirements apply:

(i) For the interior compartment to be considered open to the weather, any compartment or series of compartments from which the open space progresses must have an opening or openings meeting the requirements for end bulkhead openings, except that the opening(s) need not be located in the forward or after end of the compartment.

(ii) Open space may not progress from a space that is open under the provisions of paragraph (d)(1)(iii) of this section unless the space may also be considered open under another provision of this section.

(4) An interior or exterior opening that is temporarily closed by shifting boards dropped into channel sections at the sides of the opening is considered open to the weather if battening, caulking, or gaskets of any material are not used.

(5) An interior or exterior opening that is temporarily closed by cover plates or boards held in place only by hook bolts (see §69.123, Figure 12) is considered open to the weather—

(i) If hook bolts used to secure cover plates or boards are spaced at least one foot apart and hook over a stiffener installed around the perimeter of the opening;

(ii) If the cover plates or boards fit tightly against the weather side of the bulkhead; and

(iii) If battening, caulking, or gaskets of any material are not used.

(6) An interior or exterior opening that is temporarily closed by cover plates or boards held in place only by bolts and crosspieces is considered open to the weather—

(i) If the bolts are not installed through the bulkhead;

(ii) If the bolts and crosspieces are not held in place by cleats or other attachments to or through the bulkhead;

(iii) If the cover plates or boards fit tightly against the weather side of the bulkhead; and

(iv) If battening, caulking, or gaskets of any material are not used.

(7) Notwithstanding the opening size requirements of paragraph (d)(2) of this section, a structure with its aft end entirely open from the under side of its overhead stiffeners down to the deck, to the line of the deck, or to a coaming not exceeding three inches in height and open athwartship between the inboard faces of the side stiffeners is considered open to the weather. The opening may be covered by a wire mesh screen or temporarily closed by canvas secured at the top and lashed or buttoned in place.

(8) A structure is considered open to the weather if:

(i) Both sides of the structure are open and not fitted with any means of closing other than temporary covers meeting the requirements of paragraphs (d)(4), (5), and (6) of this section;

(ii) The openings are directly across from each other, are not separated by a bulkhead or bulkheads, and do not have any permanent obstruction within two and one-half feet of either opening; and

(iii) The openings have a continuous height of at least three feet, or the full height of the structure, whichever is less, and either extend the full length of the structure or each have an area of 60 square feet.

(e) Open space between the shelter deck and the uppermost complete deck.

(1) Space that is between the shelter deck and the uppermost complete deck and that is under cover (sheltered) but open to the weather is exempt from tonnage when all openings in the uppermost complete deck are provided with a watertight means of closing.

(2) A space is considered “open to the weather” under paragraph (e)(1) of this section when the shelter deck above the space has a middle line opening which conforms to the following:

(i) The middle line opening must be at least four feet long in the clear and at least as wide as the after cargo hatch on the shelter deck, but not less than one-half the width of the vessel at the midpoint of the length of the opening. The opening may have rounded corners not exceeding a nine inch radius. When a greater radius is required by the Coast Guard or a Coast Guard recognized classification society under §42.05-60 of this chapter, notification of that requirement must be submitted to the Commandant.

(ii) The middle line opening must be located so that the distance between the aft edge of the middle line opening and the vessel's stern is not less than one-twentieth of the tonnage length of the vessel and the distance between the fore edge of the opening and the vessel's stem is not less than one-fifth of the tonnage length of the vessel.

(iii) The middle line opening must not be within a structure of any type.

(iv) If the middle line opening is guarded by rails or stanchions, the rails and stanchions must not be used to secure or assist in securing a cover over the opening.

(v) The coaming of the middle line opening must not exceed one foot mean height above the shelter deck. Bolts must not pass through the stiffeners or flanges on the coaming, nor may there be any other attachments on the coaming for fastening a cover. Portable wood covers may be fitted over the middle line opening if held in place only by lashings fitted to the under side of the covers. Metal covers may be fitted if held in place only by hook bolts spaced not less than 18 inches apart that pass through the cover and hook over angle stiffeners or flanges fitted to the outside of the coaming. Battening, caulking, seals, or gaskets of any material may not be used in association with any middle line opening cover.

(vi) The space below the middle line opening must have a minimum length of four feet throughout its entire breadth and height and be in the clear at all times.

(vii) A scupper having a five inch minimum inside diameter and fitted with a screw down non-return valve geared to and operated from the shelter deck must be fitted on each side of the upper deck in way of the middle line opening.

(3) When the shelter deck space forward or aft of the middle line opening is divided by interior bulkheads, only those compartments with at least two openings that progress to the middle line opening are considered “open to the weather” under paragraph (e)(1) of this section. Each required opening must be at least three feet wide and at least four feet high in the clear, must not have a coaming height of more than two feet, and must not be fitted (except as provided in paragraphs (d)(4), (d)(5), and (d)(6) of this section) with any means of closing. Other compartments within the shelter deck space are not considered “open to the weather” under paragraph (e)(1) of this section.

(f) Water ballast spaces. A space, regardless of location, adapted only for water ballast and not available for stores, supplies, fuel, or cargo (other than water to be used for underwater drilling, mining, and related purposes, including production), upon request, may be exempt from tonnage if the following are met:

(1) The space must be available at all times only for water ballast that is piped through a system independent of other systems (except fire fighting and bilge suction systems). Pumps, pipes, and other equipment for loading and unloading water ballast must be of a size suitable for the efficient handling of the water ballast within a reasonable time frame. All manholes providing access to a water ballast space must be oval or circular and not greater than 34 inches in diameter. Except for those on a deck exposed to the weather, the manholes may have a coaming not exceeding six inches in height. Existing hatches over spaces being converted to water ballast spaces must have a watertight cover plate welded to the hatch and a manhole, as described in this paragraph, fitted in the plating.

(2) The primary purpose of the water ballast must be to afford a means of maintaining the vessel's stability, immersion, trim, pre-loading conditions, or seakeeping capabilities.

(3) If the space is in a vessel that is subject to inspection under 46 U.S.C. 3301, the space must be considered when determining the adequacy of the vessel's stability under 46 CFR chapter I.

(4) If the total of all water ballast spaces to be exempted from tonnage exceeds 30 percent of the vessel's gross register tonnage (as calculated under this subpart without any allowance for water ballast), a justification of the operating conditions that require the water ballast must be submitted to the measuring organization for approval. Although a single condition may justify all water ballast spaces, several conditions may be necessary in other cases. However, a particular tank is not justified by a condition if another tank already justified by another condition could be used as effectively. The justification must—

(i) Designate the vessel's service;

(ii) Explain for what purpose under paragraph (f)(2) of this section the water ballast is being used;

(iii) Include the capacity, tank arrangement, and piping plans for the vessel;

(iv) Include a statement certifying that the space will be used exclusively for water ballast as prescribed by this section;

(v) If water ballast is used for stability, describe each loading condition and the resultant metacentric height (GM) and include calculations;

(vi) If water ballast is used for immersion or trim, describe those conditions and include loading and trim calculations;

(vii) If water ballast is used for pre-loading, describe how it is used and include strength and weight calculations; and

(viii) If water ballast is used for seakeeping, describe each loading condition, GM, period of roll, and, if speed is involved, speed versus trim and draft and include calculations.

(5) If the water ballast space or its use, purpose, or piping are changed, the vessel owner or operator must report the change promptly to a measurement organization listed in §69.15 for a determination as to whether a tonnage remeasurement is required. Changes in vessel service must also be reported if a water ballast justification was required to be submitted for the vessel.

(g) Methods for measuring exempt spaces.

(1) If the exempt space is located within the superstructure, the exempt space is measured using the same procedures used to measure superstructure tonnage under §69.113.

(2) If the exempt space is located between-deck, the space is measured using the same procedures used for between-deck tonnage under §69.111(c), except that the length of the exempt space is divided into the even number of spaces most equal to the number of spaces into which the between-deck was divided.

(3) If the exempt space is located under-deck, the space is measured using the same procedures used for under-deck tonnage under §69.109, except that the length of the exempt space is divided into the even number of spaces most equal to the number of spaces into which the under-deck was divided, and the zone of influence method must be applied if the ordinary frames upon which the under-deck breadth measurements are based do not have the same depth of frame.

[CGD 87-015b, 54 FR 37657, Sept. 12, 1989; 54 FR 40240, Sept. 29, 1989; CGD 97-057, 62 FR 51045, Sept. 30, 1997; CGD 95-028, 62 FR 51203, Sept. 30, 1997; USCG-1999-5118, 64 FR 47404, Aug. 31, 1999; USCG-2011-0522, 81 FR 18727, Mar. 31, 2016]