Marine Grade Plywood is an exterior structural panel, sanded on both sides, most commonly made from Douglas fir or Pine. Other species of hardwood may also be used for marine plywood, usually in the Marine (boating) industry. Marine plywood is constructed in exactly the same manner as other exterior grade panels except that the core (inner plies) are of a higher grade where any defects are repaired, leaving no voids or voids no greater than 1/8”. The same structural exterior glue is used and the face and back veneers are usually of higher grades such as A or B.

What Is Marine-Grade Plywood?

Marine-grade plywood is a specially-designed panel made of Douglas-fir or Western Larch, according to APA: The Engineered Wood Association.

 All plies may have knots, but no knotholes.

Marine plywood is available in the following grades:

  • A-A
  • A-B
  • B-B
  • Medium-density overlay (MDO)
  • High-density overlay (HDO)  

What is Marine ply?

It’s very essential for all home owners to use what is the best material to make a product no matter what the cost be.

Areas like shipping industry, factories, etc. and for homes- in kitchen and bathrooms. For a plywood to be waterproof plywood, it needs to obey few principles like –

• The Adhesive used to glue veneers must be waterproof.
• The face and inside veneers must be of best quality veneers.

There are different grades of marine plywood viz. BWP (boiling waterproof) and PF (phenol bonded) plywood. There are few vendors who denote marine or waterproof ply as BWP and PF.

Grades Of Marine Plywood

Marine Grade plywood, considered a premium panel, can be manufactured using only A- and B-grade veneers which substantially limits the size of any knots and the number of repairs made to each veneer. Marine Grade plywood is most commonly available in a 4’ x 8’ A-B grade panel, meaning the front of the panel is an “A” and the back is a “B” grade. A-A and B-B (“face back”) grades may also be manufactured, though more typically requires a special order and a large quantity for a mill to consider such an order.
Marine Grade panels may also be finished with Medium-Density Overlay (MDO) or High-Density Overlay (HDO). These overlays of thermoset, resin-impregnated paper fibers create a hard smooth finish resistant to denting and scratching, as well as weather and chemical damage.

While its name may suggest a panel innately resistant to moisture and rot, this is not the case.

Marine Grade Plywood Vs. Sheathing

What sets Marine Grade plywood apart from other types of plywood is the number and quality of veneers and the type of adhesive used in these premium panels.

Regular sheathing plywood is manufactured with fewer, thicker layers. The interior veneers of standard plywood can contain voids and larger knots that aren’t visible until the panel is cut. Unfilled edge voids allow water infiltration that can lead to rot or delamination. All plywoods alternate the orientation of veneers to give panels strength, but the use of more and full-face veneers is what gives Marine Grade plywood its greater long-term stability and improved fastener holding quality.

This prevents delamination and further improves Marine Grade plywood durability.