You might come across these terms when looking for plywood: structural/external, non-structural/interior and marine-grade plywood. The difference lies in the glue (adhesive) used to manufacture the plywood and the plywood's strength, moisture-resistance and surface defects. Of course, these features determine where you can use the plywood and what you can use it for.
Simply put, marine-grade plywood is the strongest and most durable because it can withstand wet environments. It is followed by structural plywood and then non-structural plywood. Always remember that you should never use non-structural/interior plywood outside. Here are some important things to keep in mind.
- Structural/External Plywood
When it comes to structural plywood, be on the lookout for A-Bond and B-Bond wood. This is a kind of durability rating; A-Bond and B-Bond are both strong, but A-Bond is stronger than B-Bond.
You can use structural plywood for outdoor furniture, beams, internal structures and furniture, hoardings, boxes, bins, crates, roof and wall bracing, etc. It should, however, not be used to bear heavy loads unless combined with hardwood or softwood (solid, natural wood). Check with the manufacturer on the maximum weight and the suitable applications. The choice between A- and B-bond depends on your surroundings, plan and preference.
- Non-Structural/Internal Plywood
These types of plywood are mostly used for aesthetic enhancements, which can be wall linings, decorations, ceiling applications and furniture applications. If the decorative aspects might damage the plywood, you can either use structural plywood or apply a waterproof coating to the non-structural plywood.
You might come across C- and D-Bond grades of non-structural plywood. C- and D-Bond plywood are of a lower quality than A- and B-Bond plywood. You might even notice surface defects like knotting and graining.
It is good to mention that you might come across N-Bond grade plywood. Grade N refers to appearance; it looks smoother. You might find it hard to see any graining or knotting.
- Marine-Grade Plywood
Some applications might have severe wet environments and need special types of plywood made to withstand such environments. An example is shipbuildings where things like fungus can attack the plywood. When marine-grade plywood is being manufactured, it is treated with preservatives, very strong adhesives, varnish or paint.
Properties You Should Consider
Plywood has different properties made to match your requirements. Depending on what you want to use the plywood for, you should consider its strength, bendability and resistance to chemicals, moisture, impact, fire and water, as well as its flexibility and insulation properties. This mostly applies to structural and marine-grade plywood because these are the types used for structural purposes.