Does Plywood Outside Need To Be Treated?

Plywood is not inherently waterproof, but it is constructed by gluing together layers of wood veneer. The water resistance of plywood can vary depending on the type of glue used and any treatments applied to the surface. Exterior-grade plywood, also known as marine plywood, offers better resistance to moisture, which compromises the wood’s structure and longevity. To keep untreated plywood for outdoor use and marine-use plywood from rotting, it is essential to seal any plywood. Two types of plywood are best for outdoor use: CDX Plywood and ABX or “marine-grade” plywood. CDX is made of rough, lower-quality wood that is heavily treated for water resistance and is ideal for roofs.

Plywood is an excellent versatile building material that can be used for outdoor projects, but it must be properly sealed to protect it from the elements. This article will help you choose the right plywood for your needs. If the exterior surface of plywood is well protected, it should be quite durable, but eventually damp can cause de-lamination, even in exterior grade plywood.

Plywood is an inexpensive wood alternative, especially if you need pieces of a larger width. It is also easy to waterproof, and can be waterproofed with paint or varnish. Pressure treated plywood is often water-resistant, but it is not waterproof. Plywood does not need sealing after painting, but using a specially designed wood paint or varnish effectively seals it.

To make plywood waterproof, all plywood needs to be sealed on its edges and face if it stands a chance outside. Use exterior-rated plywood, which is made with waterproof glue, and lightly sand the plywood with 180 grit sandpaper, clean off any sawdust, and apply the desired sealant.

Is untreated plywood waterproof?

This guide explains how to waterproof plywood, a versatile building material used in DIY projects. Plywood is composed of thin layers of wood veneer, known as plies, which are bonded together with adhesive to create a strong and stable sheet called a plywood sheet or plywood panel. This cross-grain pattern enhances the strength and resistance to warping and splitting compared to solid wood, which consists of a single piece of timber. Waterproofing plywood effectively ensures its longevity and resistance to moisture damage, making it an essential tool for any DIY project.

Is exterior grade plywood treated?

Exterior plywood, despite its label, does not have rot-resistant properties but refers to the bond classification and adhesive used in manufacturing. It can be used for both interior and exterior applications. Exterior panels have a “CC” grade or better and use glue that can withstand repeated wetting and redrying or long-term exposure to moisture or high humidity. Examples include BC Tongue and Groove (T and G) Underlayment, AB Marine Grade plywood, and CC Struct1 plywood.

Exposure 1 panels use the same adhesives as exterior plywood but are not suitable for sustained exposure to weather, moisture, and humidity. They can tolerate exposure to elements but may delaminate or lose structural value over time due to other compositional factors.

What happens if you use untreated wood outside?

If your outdoor wood is untreated, it’s crucial to treat it immediately to prevent rot, fungi, and weathering. Use a wood preservative, either a wax-enriched preservative or a wax-free preserver, for an all-round coating. If the wood is dip-treated or paint-stained, it may fade after 6-12 months and provide less protection against the weather. Treat this with a wood stain, paint, or preserver. You can treat un-treated or dip-treated wood at any time.

Is it OK if plywood gets rained on?

Plywood can withstand rain exposure for a day or two without significant damage, depending on the type of plywood and the severity of the rain. However, long-term exposure can lead to serious damage such as warping, cracking, or rotting. To protect plywood from rain, it is recommended to use water-resistant types like marine plywood, apply a water-resistant sealant, and dry it out quickly if it gets wet.

In the short term, plywood can withstand exposure to rain for a day or two without significant damage. However, the ability of plywood to resist rain damage depends on various factors, including the specific type of plywood, the severity of the rain, the duration of exposure, and the specific conditions of the environment. Therefore, it is always advisable to take preventative measures to protect it, especially if prolonged exposure is expected.

Long-term exposure to rain can lead to serious damage to various materials, particularly those used in construction and outdoor settings. Over time, plywood can warp, form irregularities in shape, crack, and potentially rot. Rotting diminishes the structural integrity of the plywood, making it unsuitable for most or all of its intended uses. This failure could lead to further damage or injury.

What is the best exterior finish for plywood?

Acrylic latex paints like Diamond Vogel’s Palisade Ultra Premium Exterior Acrylic Latex, Durango Acrylic Latex Exterior Finish, or EverCryl Exterior Acrylic Latex Finish are recommended for plywood finishing due to their superior protection and durability. However, the challenge lies in overcoming the tendency towards face-checking and coating failure due to stresses induced by dimensional changes during wet-dry moisture cycling. Three options are available:

1. Use a penetrating finish that doesn’t form a surface film, preventing check and flaking. High-quality semitransparent stains highlight the architectural intent of textured plywood siding, adding color and beauty to the rustic, rough texture. However, repairs made on the veneer face of the plywood will also show through the finish.

2. Apply two coats of Diamond Vogel’s Grain Stain Semi-Transparent Stain or Grain Stain Semi-Solid Stain to rough texture plywood. Allow time for the first coat to soak into the wood, and remove excess after the second coat to ensure even application. A full panel should be done at one time to minimize lap marks.

What is the best protection for exterior plywood?

The use of water-based paints and drying oils is an effective method for waterproofing outdoor plywood. However, it should be noted that these materials may require periodic touch-ups or repainting to maintain optimal effectiveness. Tung oil is an optimal selection for exterior applications.

How do you treat plywood for outdoor use?

To waterproof plywood, a variety of materials may be employed, including epoxy, waterproof paint, oil, varnish, latex, or PVA. These materials are suitable for use in both indoor and outdoor settings. These materials are available in both paint-on and spray forms and bond readily to the wood, thereby protecting it from moisture.

Does plywood need to be treated for outdoor use?

Untreated plywood is vulnerable to moisture and water rot, leading to fungus or mold growth, affecting its integrity and potentially breaking down over time. The plys within the board are created through glueing and pressing, but the glue used is not generally waterproof, causing irreparable damage if disintegrated. Plywood edges, which absorb moisture faster than the surface, are weak spots, making it crucial to seal them to protect the board.

Will plywood be OK outside?

Exterior plywood, often made from Douglas fir, is weather and water resistant, making it suitable for outdoor use in areas exposed to water and humidity. It can be used on decks, walkways, sheds, outdoor shelving, and outdoor structures like gazebos, benches, or planters. There are various types of exterior plywood, with the most common being CDX or ACX. The construction grade is indicated by an X, with A being a premium grade for high-end uses and CDX being a more affordable option.

The plywood layers can be made from veneers, high-density hardwood, or light hardwood. While it may not be visually appealing due to visible knots or blemishes, some types have cleaner appearances, making them ideal for projects requiring aesthetic appeal. The construction grade is indicated by the first two letters, indicating the plywood’s construction grade.

How long will untreated ply last outside?

The longevity of untreated wood varies considerably, depending on a number of factors, including the specific type of wood, the climate in which it is situated, and the extent to which it is exposed to the elements. In general, however, wood can be expected to last for a period of between a few months and several years. Woods with natural decay resistance, such as cedar and redwood, have been known to last up to 20 years or more.

What happens if untreated plywood gets wet?

It is common for plywood to undergo dimensional changes when stored in an environment with high humidity for an extended period. This phenomenon is particularly prevalent when the plywood is stored outside prior to use. The layers of the plywood may split apart as a result of this dimensional change, especially when the plywood is stored outside before a project begins.