AB marine-grade, pressure-treated plywood offers superior protection against fungal decay in wet environments. It is approved for saltwater applications and offers excellent corrosion resistance.
Well, marine grade plywood is regarded as the best outdoor plywood, and is extensively used for construction. There are other construction materials that can be used for building exterior structures like oriented strand board (OSB) or ACX, but marine grade plywood outshines them all.
Pressure treated plywood resists damage from water, weather, decay and insects. Plywood with tongue and groove edges are designed to snap together easily while creating a strong and tight joint between panels.
While similar to standard exterior plywoods, marine plywood is the highest quality (AA, AB, and BB), constructed from wood without knots. Eliminating the knots in wood improves durability because it practically eliminates the possibility of water pockets forming within the wood.
BWR Grade Plywood
This is used for both interiors and exteriors, being treated with phenolic resins to make it water resistant. Unlike MR grade, BWR grade plywood is good for use in areas that have prolonged exposure to water, for example, in kitchens and bathrooms.
AB marine-grade, pressure-treated plywood offers superior protection against fungal decay in wet environments. It is approved for saltwater applications and offers excellent corrosion resistance. It is also safe for human and aquatic environments.
Keep in mind that this kind of plywood is water resistant, not waterproof, and can still be ruined from a leaking tub or toilet. CDX plywood is often used under shingles and roofing felt, on walls (just behind the siding and insulation), and as a sub floor just under the carpet pad or a tiled floor's durock.
Do you need to waterproof OSB? To answer the question “Is oriented strand board waterproof?” the answer is: not completely. That's because it's virtually impossible to prevent some water absorption in a wood-based product, and moisture can be absorbed through cuts in the panel and the wood strands can swell.
Use polyurethane varnish for dependable waterproofing, wood stain for weather-proofing, oil for a cheap, light sealant, or epoxy for a more thorough, durable finish. Sand your plywood before applying any sealant. Make sure your sealant of choice coats the plywood completely for total waterproofing.
Aircraft plywood is the most durable type available. It uses hardwoods to create strong boards that can resist heat and moisture. Aircraft plywood is made of very thin veneers, which keep it light and flexible while providing significant strength.
They work equally well for these uses, are just as easy to drill into and have equivalent ability to hold nails. However, OSB is generally considered less resistant to water (it swells in thickness when exposed to moisture) and some people prefer plywood for roofs and subfloors.
Waterproofing plywood not only protects it from outside humidity but from fungal growth as well. Sealing plywood protects it from the conditions which often lead to dry rot. In the end, you should waterproof plywood for both indoor and outdoor projects, as doing so will not only prevent warping but rotting as well!
The outdoor elements can take a toll on wood and make it look less than pristine. Pressure treatment helps protect wood from rot and insects with the help of high pressure and preservatives, helping to extend its life. Generally, pressure-treated wood can last anywhere from 10 to 40 years, depending on a few factors.
PLYWOOD – EXTERIOR PLYWOOD
It is usually made from softwoods such as Douglas Fir or Pine. A structural exterior (water resistant) adhesive is used to adhere the veneer layers together. The higher grade panels are sanded on both sides and are sometimes referred to as Sanded Plywood or Sanded Panels.
Marine plywood is specifically manufactured to stand up to the harsh marine environment. The materials used in in its construction are specifically chosen to assist in making it as water resistant as possible. Pressure treated plywood is usually regular softwood and will absorb moisture very easily.
OSB is less expensive than plywood. To build a typical 2,400-square foot home, OSB may cost $700 less than plywood. OSB is considered by many to be a “green” building material because it can be made from smaller-diameter trees, such as poplars, that are often farmed.
Wood fiber is used more efficiently in osb. Osb is stronger than plywood in shear. Shear values, through its thickness, are about 2 times greater than plywood. This is one of the reasons osb is used for webs of wooden I-joists.
Plywood can be waterproofed in 5 ways. With epoxy sealer, drying oil, liquid latex, water-based paint or varnish. The general process is to start by lightly sanding the plywood with 100 to 180 grit sandpaper, remove any sawdust, apply the waterproofing finish and then let it dry.
What Happens if Plywood Is Stored in Wet Conditions? Generally, if common plywood gets wet for an extended period of time, it can swell and lose shape which eventually leads to the layers of wood splitting apart.
When plywood gets soaked with water, it usually swells and will eventually rot. However, if your plywood does get wet, there is no need to panic as plywood usually takes at least a few weeks to decay, especially if you live in a cool and dry climate.
On average OSB is 7% less stiff than CDX, however, OSB is stronger than CDX in shear according to a study done by University of Massachusetts. Additionally, when the APA, The Engineered Wood Association, rate plywood, it rates them as equivalents. (As they rate spans, not whether it's OSB or CDX.)
CDX, while being well-known and widely used, is not the best option for discerning and high-end projects. CCX, with it being a higher grade, between a 5- and 6-ply product, free of major knots, and less known, makes it the better option for any project you're working on.
CDX stands for: C – veneer grade for one strip of plywood. D – veneer grade for one strip of plywood. X –glue used to connect both veneers.