Marine plywood (moisture-resistant plywood) is produced from special types of wood, such as Okume, Meranti, Gurjan, Birch, etc., but the best quality have an Okume, because Okume has excellent resistance to insect, fungal and rot attacks and also weatherproof. It is also possible to order marine plywood from khaya mahogany, sapele, teak, etc.
BS 1088 is the British Standard specification for marine plywood that applies to plywood produced with untreated tropical hardwood veneers that have a set level of resistance to fungal attack. The plies are bonded with Weather Boil Proof (WBP) glue.
The standard is associated with Lloyd's Register since it performs testing of products to this standard. It does not follow that it is a structural plywood.
WBP Glue Line -- BS 1088 plywood must use an adhesive, which has been proven to be highly resistant to weather, micro-organisms, cold and boiling water, steam and dry heat. The product's bonding must pass a series of British Standard tests. The glue that is used to glue the layers of marine plywood together must pass a strict test - the WBP or Water and Boil Proof Test, where the durability of the plywood is tested in extreme conditions, i.e. the plywood is boiled in water for about 72 hours and the plywood layers must not come off the glue.
Face Veneers -- These must present a solid surface that is free from open defects. Face veneers must be free of knots other than "sound pin" knots, of which there shall be no more than six in any area of one square foot, and there can be no more than an Average of two such knots per square foot area over the entire surface of the plywood sheet. The veneers must be reasonably free from irregular grain. The use of edge joints is limited, and end joints are not allowed.
Core Veneers -- Core veneers have the same basic requirements as face veneers, except that small splits are allowed, and there is no limit on the number of pin knots or edge joints. However, end joints are not permitted.
Limits of Manufacturing Defects -- Defective bonds, pleats and overlaps, and gaps in faces are not permitted. Occasional gaps may be repaired using veneer inserts bonded with the proper adhesive.
Moisture Content -- BS 1088 plywood must have a moisture content between 6% and 14% when it leaves the factory. The certified factory is audited in accordance with the requirements to ensure the highest quality.
KOMO guarantees that the quality has been objectively tested by independent experts. An additional guarantee that the product meets environmental protection, health and safety requirements.
Marine plywood is classified:
Exterior2 is moisture-resistant and suitable for use in places where there is no direct contact with water, such as yacht or ship cabin interior, etc.
Exterior3 is waterproof and can be used in wet conditions, such as yacht decks, outdoor furniture, planter boxes, benches, etc. The glue used to glue the exterior plywood together is waterproof, which ensures that the plywood layers stay together in wet conditions. Marine plywood must be finished and maintained with special boat oils and varnishes.
AS MASS sells marine plywood that is moisture and/or waterproof:
- Lloyds Marine Plywood certified.
- with KOMO certificate.