How To Seal Plywood For Outdoor Use: 5 Best Methods (2024)

How to seal plywood for outdoor use? Learn how towaterproof plywood for outdoor use and protect it from rain and snow! Discover the best products for waterproofing plywood for outdoor use.

> Read more: plywood sizes, 3/4 plywood, 4×8 plywood, 1/2 plywood, 5/8 plywood, 1/4 plywood

Do You Need to Seal Exterior Plywood?

Yes, exterior plywood needs to be sealed before use outdoors or in high moisture areas such as bathrooms and kitchens. Plywood is not naturally waterproof or rot-resistant, and unsealed plywood is at risk of warping, splitting, or degrading over time.

Benefits of Sealing Plywood

  • Enhanced Strength: Sealing makes plywood stronger.
  • Attractive Finish: Waterproof paint can give it a pleasant appearance.
  • Versatility: Sealed plywood can be used both indoors and outdoors.

Problems Without Sealing

  • Peeling Apart: Moisture can cause the layered structure of plywood to separate, even with pressure-treated plywood.
  • Warping: Unsealed plywood can warp when exposed to water, compromising its structural integrity.
  • Rot: Unsealed plywood is susceptible to rot from weather exposure or moisture infiltration.
  • Fungal Growth: Fungus and mold can grow on unsealed plywood exposed to moisture, posing health risks.

Usage and Application

Engineered plywood is strong and lightweight, making it suitable for structural work, outdoor furniture, and landscaping projects. By sealing it properly, you can protect it from the elements and ensure its longevity and performance in various applications.

> Read more: laminate flooring, hardwood flooring, baltic birch plywood, maple plywood, ACX plywood, BBOES plywood

Do You Need to Seal Exterior Plywood?
Exterior plywood needs to be sealed before use outdoors

Benefits of Sealing Plywood

Sealing plywood has any advantages. It will save you from extra expenditure and your wood from decaying.

1. Prevention of Rotting

All exterior woods are prone to gel mold due to its nature and other factors like humidity. a rot makes a wood damaged and also destroys its appealing look. Rot can be developed on ply-wood in various ways. The best way to protect it from any type of mildew is by sealing it.

Sealing ply-wood properly and efficiently will save you from future trouble.

2. Protection From Sun and Moisture

If water penetrates plywood, it just not only cause rot. Extra water penetration can cause wood to break. This can largely damage your plywood material. To prevent it from happening, seal your wood as soon as possible.

Sunlight rays also damage the wood. More intense exposure to the sun will result in the twisting of wood. This can cause wood to lose its natural beauty and structural integrity. Sealing plywood will help to maintain its structure and appearance.

3. Balance Sheet

Sealing wood will reduce its chances of splitting. Sealing keeps plywood strong and prevents it from shrinking, expansion and twisting. A balanced wood surface will reduce the chances of wood warping.

> Get more details: 

Benefits of Sealing Plywood
Sealing plywood has any advantages

What to Use for Sealing Plywood

When sealing plywood, different products are suited for different applications. Here’s a guide to help you choose the right product for your project:

Drying Oil

  • Characteristics: Light sealant that retains the natural look and feel of wood.
  • Application: Soaks into the layers to form a thin barrier against moisture.
  • Uses: Ideal for deck fittings, work surfaces, and marine use.

Epoxy

  • Characteristics: Preferred method for sealing and waterproofing. Acts as both an adhesive and a plywood sealer.
  • Application: Provides additional strength and protection, can also be used as a primer for painting.
  • Uses: Suitable for both indoor and outdoor structures, especially exterior buildings prone to weather damage.

Waterproof Paint

  • Characteristics: Water-based paint designed for outdoor use, provides waterproofing and color.
  • Application: May require sanding and touch-ups over time for long-lasting results.
  • Uses: Perfect for sheds, landscaping work, and any outdoor structures.

Varnish

  • Characteristics: Hard, moisture-resistant coating with a shiny finish. Expands and contracts with weather changes.
  • Application: Suitable for faces and edges of plywood.
  • Uses: Great for boats, decking, and furniture.

PVA (Polyvinyl Acetate)

  • Characteristics: Easy to apply, dries clear, and gives a smooth finish. Non-toxic and safe for home use.
  • Application: Often diluted with water before applying.
  • Uses: Good for internal structures like shelves and wood paneling, and can be used as a primer before painting.

Liquid Latex

  • Characteristics: Available as a liquid or spray, bonds well to plywood.
  • Application: Fast and easy to apply, though can be more costly.
  • Uses: Suitable for interior wood in bathrooms to exterior wood like decking, boats, and sheds.

Tips for Choosing the Right Product

  • Read the Label: Ensure the product matches your intended use.
  • Consider the Environment: Choose a product that suits the exposure conditions (indoor vs. outdoor).
  • Evaluate the Finish: Decide if you want a natural look, color, or a shiny finish.

> Learn more: types of wood, Types Of Plywood, marine plywood, birch plywood, MDO plywood, hdo plywood

What to Use for Sealing Plywood
When sealing plywood, different products are suited for different applications

How to Seal Plywood for Outdoor Use: Step by Step Guideline

How can I waterproof plywood? Following are some steps taken during sealing of plywood:

  • First, all sides of plywood are sanded by using sandpaper of 80-grit measurement. It is better to sand in back and forth motion and along the natural grain of the wood rather than across the natural grain.
  • To get a smoother finishing touch, sanding is repeated with 120-grit sandpaper. Sandpaper of higher grit can also be used for an even better smooth finish but in the case of plywood, it is not required.
  • By using a clean cloth, plywood dust is wiped off. For applying a sanding sealer, a dust-free and clean area is required. You also need a clean paintbrush to apply the sealer.
  • With the help of a clean paintbrush, sanding sealer is applied on the plywood in even and leveled brush strokes to coat the surface. Unevenly coating saturates the surface making it rough. The essential element for a proper and smooth finish is even coating. Let the coating of sanding sealer dry, as instructed by the manufacturer. If you wish to seal both sides of the plywood, do it in steps. First, finish one side and let it dry. Then seal the second side.
  • Now, the sealed surface is again sanded using 120-grit sandpaper. This light sanding removes the bumps caused by the first sanding and cause airspaces (left from sealing) to diminish. Sand till you get a smooth touch but without damaging the sealing. This causes the plywood to appear waxy.
  • In this step, a final coating of the sanding sealer is applied and allowed to dry. This gives plywood a long-lasting finish.

> Learn more: 

How to Seal Plywood for Outdoor Use
How to Seal Plywood for Outdoor Use

3 Common Technique For Outdoor Plywood Sealing.

To ensure a long life of plywood outside, it is necessary to weatherize it. You can simply do it by yourself with the help of the following methods. This whole project will just require only 1-2 days.

1. Polyurethane Varnish

One of the best methods to seal edges of plywood outside is by applying exterior polyurethane varnish. You will require the following materials.

  • Small brush
  • Varnish
  • Masking Tape

Apply a coat of polyurethane varnish to the edge of a wood with the help of a brush. Avoid it using on the surface of the plywood. Cover the surface with masking tape. Do a full coverage with tape to block varnish.

If varnish gets a hold on the plywood surface, it will not allow the wood to absorb any future wood treatment. Now after 1st coat, wait for 30 minutes. After that, apply several layers of varnish for the best results.

This treatment of plywood edges will prevent it from water penetration. It also helps to save it from dreadful weather conditions.

2. Water-Based Stain

Cover the entire surface of the plywood with a coat of any exterior water-based stain. These stains are very light in color and do not show any bright shade. These work best for protecting the surface against strong UV rays. Grab the following material

  • Pump-up Sprayer
  • Cloth rag
  • Water-based pigment stain

With the help of a garden or pump-up sprayer, apply the stain. Allow it to dry for several minutes. Drying time will always be mentioned in the stain container. For best results, follow the mentioned timeline.

After spraying the whole surface, use cloth rage to clean any excess or dripping stain. Keep in mind, this water-based pigment stain is not proposed to completely paint your plywood. They will give a light color and protection to your wood from sun damage.

For the best effect, leave your wood for at least 24 hours after applying the stain coat.

3. Water Seal

This sealer is great for guarding plywood against water penetration. It is a good wood conditioner and doesn’t block all pores of the wood.

Things you will need are as follows.

  • Water sealant
  • Garden sprayer

Take a garden pump-up sprayer. Apply a coat of water seal to your plywood. After smoothing the surface, apply another coat. Use several coats of sealant to get a maximum result against water penetration. It is best to reapply sealant after every 2 years.

A wide range of water sealants can be easily found in any kind of paint store. They usually come under manufacturer’s names.

3 Common Technique For Outdoor Plywood Sealing.
3 Common Technique For Outdoor Plywood Sealing.

How to Seal Plywood Edges

Sealing plywood edges can be challenging if the wood is uneven. Follow these steps for a successful seal:

  1. Sand the Edges: Ensure the edges are smooth and even before applying the waterproofing seal.
  2. Apply the Sealant:
    • Use a brush or spray to apply the sealant, making sure it penetrates into crevices and fine cracks to prevent moisture from getting in.
    • Sealing pastes and tapes specifically designed for plywood edges can also be used for added protection.

By sanding properly and using the right application method, you can effectively seal plywood edges and protect them from dampness.

Which Plywood to Choose For Outdoor Use?

There is a variety of exterior plywood and it is important to know which one will benefit you the most. If not selected properly, sealing will not be useful. It will be prone to become rotted, soft, and break. The most common types of exterior plywood are CDX, marine-grade, pressure treated, OSB, and T-11.

Marine-grade exterior plywood has knot-free sheets and is mostly used for decking, porches, planters, and arbors. CDX is the most commonly used plywood. It normally comes in piles of 3, 5, 7, 9, and the lowest number indicates the uppermost class of a CDX plywood. They are widely used in the construction industry and for the roofing of buildings.

Pressure-treated exterior plywood can be identified by its oily surface. It is prepared by infusing regular plywood with different chemicals under a certain pressure. These chemicals treatment makes this wood strong against rotting and mildew.

The main purpose of OSB plywood s is roof decking. It is manufactured with a water-proof glue and provides safety against excessive moisture. T1-11 is mostly used for sidings.

The best thing about this plywood is that it can be painted with natural color and can be well-matched against different color varieties.

  • If you have a limited budget use a CDX plywood. A Urethane coated CDX has very strong resistance against weather conditions.
  • While working with horizontal installations, pressure-treated plywood is a good choice. This wood lasts longer even in unfortunate drainage systems.
  • If you are working on a project that includes outdoor vessels for water flow, prefer marine-grade plywood. This type of wood is expensive but strongly resists moisture. It is perfect to use it for underwater applications like boats.
  • If you are working on any siding project, choose a T1-11. This type of wood is also good for big exterior wooden boxed. It can be easily stained for any desired color and appearance.
Which Plywood to Choose For Outdoor Use?
Which Plywood to Choose For Outdoor Use?

How to seal plywood for outdoor use: FAQs

Below is some questions about how to seal plywood for outdoor use:

What can I put on plywood to make it waterproof?

Sealing plywood faces and edges prevents water from damaging the wood. Use waterproofing epoxy, varnish, paint, or oil. Apply these after sanding, using a spray, roller, or brush.

How do you seal untreated plywood?

To waterproof plywood, use epoxy, waterproof paint, oil, varnish, latex, or PVA. These sealants come in paint-on or spray forms and bond easily to wood. Simply sand the surface, apply the sealant, and allow it to dry.

Do I need to seal plywood after painting?

No, sealing plywood after painting isn’t necessary. Painting with specially designed wood paint or varnish effectively seals and protects it from moisture. For added waterproofing, use a sealing product, primer, or waterproofing undercoat before painting with weatherproof paint.

Should you seal both sides of plywood?

It’s not always necessary to seal both sides, especially if only one side is exposed. This can save time and money. However, if all sides are exposed to the elements, ensure all surfaces are sealed.

Should you seal both sides of plywood?
Should you seal both sides of plywood?

Can I seal plywood with PVA?

Yes, PVA glue can be used for waterproofing plywood or as a primer before painting. It’s non-toxic and safe for home use, making it ideal for sealing internal plywood structures like shelves and wood paneling.

Can you use emulsion on plywood?

Emulsion paint isn’t designed for wood and may not adhere well or be long-lasting. Use paint specifically designed for wood, with a primer or wood seal product underneath. Sand the wood, wipe it down, and seal it before painting.

How do you seal plywood for indoor use?

Sealing plywood indoors protects it from moisture damage and warping. Use waterproofing epoxy, oil, paint, varnish, PVA, or liquid latex. This is particularly important in areas prone to leaks or high moisture levels.

Can You Seal Plywood for Outdoors?

Yes, you can seal plywood for outdoor use. The most durable and effective method is by applying Type-A waterproof glue sealant. This type of sealant is commonly used by reputable plywood suppliers, especially on marine and heavy-duty plywood. Here are the key points:

  • Type-A Waterproof Glue Sealant: This provides a highly durable and effective waterproofing solution for plywood.
  • Marine and Heavy-Duty Plywood: Most marine and heavy-duty plywood come pre-sealed with this type of sealant.
  • Application: If your plywood isn’t pre-sealed, you can apply the Type-A waterproof glue sealant yourself to ensure it withstands outdoor conditions.

Using Type-A waterproof glue sealant will help protect your plywood from moisture, making it suitable for outdoor projects.

Best Treatment for Exterior Plywood

For exterior plywood, two effective treatments are commonly used:

Drying Oil (e.g., Tung Oil):

  • Ideal for outdoor use, drying oil like Tung oil penetrates plywood sheets to create a protective coat. It retains natural flexibility and moisture, enhancing durability against weather elements.

Liquid Latex:

  • Liquid latex offers an easy application method for sealing plywood. It forms a durable, waterproof layer that effectively protects the plywood from moisture and environmental damage.

These treatments provide reliable protection for exterior plywood, each offering unique benefits depending on your project’s requirements.

Best Treatment for Exterior Plywood
Best Treatment for Exterior Plywood

Conclusion

Now you have become familiar with our guide on how to seal plywood for outdoor use. Always select suitable plywood for your exterior project and then seal it step by step. The above techniques are used by professional woodworkers to extend an exterior plywood life.

Above mentioned methods and tips are also valuable for protecting edges of the wood. Sealing edges of the wood are significantly important because they are more exposed to weather conditions. If you seal plywood flawlessly, it will enhance your wood resistance capacity.

We are sure that you have got complete knowledge of sealing plywood and will be able to seal your wood like a pro!

Vietnam Plywood

Vietnam Film Faced Plywood

by: