Storeroom Painting: Coat Coverage, Container Sizes, and a Change Order
During a shipyard availability, a working party is assigned to paint a shore-side storeroom measuring 24 feet long, 18 feet wide, and 9 feet high. The job covers the four bulkheads and the overhead; the deck is not painted. Two openings are masked off and receive no paint: a door 3 feet by 7 feet and a ventilation opening 4 feet by 2 feet. The specification calls for two coats on every painted surface. Standard paint is issued only in 5-gallon pails costing $92 each, and one gallon covers 350 square feet. A commercial equivalent covers 400 square feet per gallon, is sold only in single gallons at $24 each, and needs the same two coats. After the job is scoped, a change order adds two overhead beams, each 30 feet long and 1 foot deep on the exposed face, which must also receive two coats.
1. Compute the total area to be painted, including the change order, and the gallons of standard paint required for both coats.
Read the worked answer
Bulkheads. Perimeter = 2(24 + 18) = 84 feet. Area = 84 x 9 = 756 square feet.
Overhead. 24 x 18 = 432 square feet.
Gross area. 756 + 432 = 1,188 square feet.
Openings. Door 3 x 7 = 21; vent 4 x 2 = 8; total 29 square feet.
Net area before change. 1,188 - 29 = 1,159 square feet.
Beams. Each contributes 30 x 1 = 30 square feet of exposed face, so 60 square feet.
Total per coat. 1,159 + 60 = 1,219 square feet. Two coats = 2,438 square feet.
Gallons. 2,438 / 350 = 6.97, so 7 gallons are needed. Without the beams the figure was 2,318 / 350 = 6.63, also 7 gallons.
2. How many pails must be purchased, what do they cost, and how much paint is left over? Does the change order force a third pail?
Read the worked answer
Standard paint comes only in 5-gallon pails, so 7 gallons cannot be bought as 7 gallons. Divide by container size and round up: 7 / 5 = 1.4, so 2 pails, or 10 gallons, at 2 x $92 = $184.
The change order does not force a third pail. Usage moves from 6.63 to 6.97 gallons, and both round up to the same two-pail purchase. That is the useful conclusion: the change costs labor time but not material money.
Leftover is 10 - 6.97 = 3.03 gallons. Storing it properly matters; a partially used pail that skins over is money already spent, and the 350-square-foot figure assumes a full-strength, well-mixed gallon.
3. A junior sailor proposes buying the commercial equivalent instead and claims it saves about $40. Evaluate the cost comparison after the change order.
Read the worked answer
Commercial coverage is 400 square feet per gallon: 2,438 / 400 = 6.095 gallons, which must be bought as 7 single gallons at $24 = $168.
Savings against the $184 pail purchase = $16, not $40.
The $40 figure comes from using the pre-change area: 2,318 / 400 = 5.795, rounding to 6 gallons, $144, a $40 saving. Adding 120 square feet of beam area pushed the requirement just past 6 gallons, so the seventh gallon has to be bought.
Cost per square foot of usable paint also matters: the pail option leaves 3.03 gallons spare, which is convenient for touch-up, while the commercial option leaves 0.905 gallon. The $16 difference is small enough that availability and drying time, not price, should decide.