Permeability of a space in a ship is the percentage of empty volume in that space.
Permeability is used in ship survivability and damaged stability calculations in ship design. In this case, the permeability of a space is a percentage from 0 to 100. Alternately, the permeability may be a coefficient from 0 to 1. The permeability of a space is the percentage of volume of the space which may be occupied by seawater if the space is flooded. The remaining volume [not filled with seawater] being occupied by machinery, cargo, accommodation spaces, etc.
Typical values from the International Bulk Chemical Code are:
- 0.95 for voids (empty spaces), tanks, and living spaces
- 0.85 for machinery spaces
- 0.60 for spaces allocated to stores.
This implies that for damaged stability calculation purposes, machinery spaces are only 15% full with machinery by volume (100% - 85% = 15%).
- Title 46 U.S. Code of Federal Regulations