ISO 11812:2020

ISO 11812:2020 - Overview

ISO 11812:2020, "Small craft - Watertight or quick‑draining recesses and cockpits", specifies performance requirements and test methods for watertight and quick‑draining recesses and cockpits in small craft up to 24 m load line length. The standard covers watertightness, draining time, companionway sill heights and gravity‑drain design. It applies to recesses located in elevated parts of the craft and addresses normal operation only - pumping or unattended craft drainage are out of scope. ISO 11812 does not prescribe recess size, shape or location and does not replace stability or buoyancy requirements in ISO 12217 series.

Key topics and technical requirements

• Watertightness levels: Criteria and test procedures distinguishing “watertight” and “quick‑draining” recesses, including watertightness and weathertightness assessments.
• Companionway sill requirements: Definitions of sills covered, measurement methods and minimum sill height principles for quick‑draining recesses.
• Drainage design: Mandatory drainage requirements for single‑bottom and multi‑bottom recesses, including number, dimensions and installation of drains.
• Draining time calculations: Full calculation method (normative) and simplified assessment methods to size drains and verify required draining times under gravity flow.
• Hydraulic details: Guidance on head loss coefficients, non‑circular drain dimensions and differing drain diameters (Annex A).
• Testing and examples: Normative watertightness tests (Annex C) plus informative worked examples and technical background to support calculations (Annices B, D, E).
• Documentation: Owner’s manual requirements and documentation to inform safe operation and maintenance.

Practical applications and users

ISO 11812 is designed for professionals and organizations involved in the design, manufacture, certification and operation of small craft:

• Naval architects and boat designers specifying recess and cockpit drainage and sealing.
• Boat manufacturers and outfitting suppliers sizing drains and companionway sills.
• Surveyors, classification societies and regulators assessing compliance.
• After‑sales engineers and maintenance personnel preparing owner’s manuals and installation guidance.
• Safety officers and marina operators evaluating risk of flooding through recesses.

Use cases include cockpit and deck recess design, companionway configuration, drain system verification, and producing compliance documentation for boats up to 24 m.

Related standards

• ISO 12217‑1 / ‑2 / ‑3 - stability and buoyancy for small craft (stability implications of retained water are addressed there).
• Other ISO and national maritime safety and construction standards referenced in ISO 11812.

Keywords: ISO 11812:2020, watertight recesses, quick‑draining recesses, small craft drainage, companionway sill, draining time, watertightness tests.