Permeability (compartment)

Permeability is the fraction of a compartment’s volume that floodwater can actually occupy, the rest being taken up by structure, machinery, or cargo. It scales the volume of water admitted and so the loss of buoyancy and added free surface in a damage case. SOLAS Chapter II-1 sets standard values: 0.95 for void and accommodation spaces, 0.85 for machinery spaces, 0.60 for stores, and load-dependent values for cargo and dry-cargo spaces (commonly 0.70 to 0.95 depending on draft). The probabilistic damage rules apply these permeabilities when computing the attained index A. A higher permeability admits more water and worsens the damaged condition.