Marine Plywood vs. Exterior Plywood for Deck Repair

Marine

• Marine plywood is at the head of the class when it comes to grades for plywood. Marine plywood panels typically have an A-A, A-B, B-B grade, according to the American Plywood Association. This means that the front and back sides of the panel are always at least of B-grade in appearance quality. In terms of deck repair, this gives you comfort, knowing that you have used the highest-grade plywood. Marine plywood is manufactured to endure exposure to water and moisture, whether you’re repairing a deck in your back yard or the deck on your boat.

Exterior

• Exterior plywood is also constructed to withstand exposure to extreme outdoor weather conditions. It is distinguished from interior-grade plywood by the type of glue that is used to bond and adhere the veneer plies to form the plywood panel. In the United States, exterior plywood panels, which bear the American Plywood Association label, are manufactured with a fully waterproof bond. Glues used to bond the plies for exterior plywood are made to withstand moisture and extreme weather conditions, which are important considerations when you are repairing a deck. You don't want the plies to dislodge, warp or bend.

Similarities

• Marine and exterior plywood are similar to other types of plywood, in that they are made from several layers, or plies. In most cases, the plywood panel is made of an odd number of plies, with three, five and seven plies being the most common. The plies are bonded together with glue under intense heat and pressure to create a solid, stable panel. The glues that are used are specifically made for exterior applications to reduce the occurrence of delamination, in which the glue between each ply loosens and detaches from the plies above or underneath. You can use marine or exterior plywood to make repairs on all types of exterior decks, including backyard decks and decks of marine crafts.

Differences

• Using marine-grade plywood reduces the amount of surface preparation you need to make if you are seeking a material that provides an attractive base to work with. Marine-grade plywood has fewer voids and gaps between the plies, which makes it less apt to trap and hold moisture. Exterior plywood, on the other hand, is allowed to have voids and gaps for an A, B or C rating by the American Plywood Association, in comparison to marine-grade plywood.

  Douglas fir and western larch are most commonly used to manufacture marine plywood. These wood species can withstand exposure to moisture better than other wood species. As a result, if you live in a climate with high humidity or that experiences lots of rain or snow, marine-grade plywood has inherent properties that make it a more sustainable choice for deck repairs.