Birch is a strong and durable hardwood popular among woodworkers and DIYers. It is an excellent choice of wood for making veneers, plywood, pulpwood, and other woodworking projects. But is birch good for outdoors and can it withstand harsh external elements?
To use this wood best, allow our pro woodworkers to explore birch wood and understand its capacity as one of the finest hardwoods.
About Birch Plywood: How It’s Structured + Grades
With a Janka hardness of 1,260 lbf (5,610 N), you can choose from two types of birch plywood: plain or regular and baltic birch plywood. Both need a proper sealant to prevent early decay and rot after prolonged exposure to water and direct sunlight.
Birch plywood is composed of more than two layers of veneers. Each birch veneer measures less than 1/8 inch thick. Layers glue together when heated at a high temperature of at least 284oF (140oC).
Once the veneers are completely patched, manufacturers re-sized or sanded the plywood for commercial availability. For your woodworking, you can choose from UV-coated plywood for decks, thin-flexible, laminated birch, patterned, and exterior plywood.
Depending on where you need plywood, they come in higher and lower grades based on their smoothness and finish.
Higher grades of plywood are B/BB, S+/BB, and BB, offering a high-quality finish with smooth surfaces. While lower grades such as BB/CP and BB/WG, CP, C, and WG work well for concrete forms and packaging, it has a rough texture.
These wood-based multiple layers boards have offered good structural integrity and caused birch plywood to be dimensionally stable. It’s considered an essential material in making outdoor furniture today.
Is Birch Wood Good for Exterior Furniture?
Birch is a versatile wood that can be used outdoors. You can have walls, claddings, ceilings, sofas, and tables made of birch as outdoor furniture. These types of furniture have an aesthetic finish with a beautiful color and grain pattern.
But since it has low resistance from harsh environments outside, you must apply a good finish to your birch wood furniture to improve resistance from extreme weather, pests, and insect attacks.
You should also use treated birch for your outdoor application to minimize maintenance and ensure a longer lifespan for your furniture. Otherwise, your birch furniture will be prone to insect attacks, warping, and expansion and could be less stable.
Is Birch Water- and Weather-Resistant?
Birchwood has low resistance, particularly from water and extreme weather conditions. It is easily expanded and contracted, which can damage your furniture eventually. Like pine, it is a diffuse-porous [1] hardwood. It has medium pores, enabling water to penetrate the wood easily.
Also, birch plywood cannot withstand prolonged exposure outside without proper waterproofing since it has poor water-resistant like pine. So you must apply sealers, preventing delamination, rot, and decay over time. Other drawbacks could affect the stability of your plywood.
Wood is biodegradable and has only a certain point before water affects it after prolonged exposure. For example, if unsealed or untreated baltic birch plywood is exposed to the wet ground or has been wet massively, it will lead to bowing and cupping.
Once the plywood reaches 20% or more than the low-level moisture it can sustain, it will be susceptible to insect and pest attacks. Also, molds and fungi will accumulate, weakening and damaging the wood from the inside.
Therefore, you must apply a waterproofing sealer to protect your wood. You can use varnish or oil stains to accentuate the yellow or reddish-brown natural color of birch, aside from adding a protective layer on the surface.
Is Birch Wood Environment-Friendly?
Birch is considered environment-friendly, making it more versatile because of being a non-toxic wood, making it safe for various kitchen fittings and children’s toys.
This wood is also sustainable because it can survive strong winds for at least eight to 12 years. It has 40 species that come from the Betula genus. But the popular birch tree species that thrive abundantly and are native to the United States and Canada are Yellow, Paper, and Sweet birch.
So, when used by manufacturers, it is only locally transported as it can be sourced from many forests in the US, reducing carbon emissions.
Will Birch Wood Rot Easily?
Birchwood is prone to quick decay and rots when you use it outdoors without proper waterproofing sealing. This wood has low moisture- and water-resistant, which could penetrate birch wood, accumulating mold and fungi.
Therefore, apply a quality sealer before using wood, particularly outdoor furniture. And to keep it in good condition, you must apply a protective coat.
Birch Wood for Outdoor Use: Advantages & Disadvantages
Pros
- Affordable
- Lightweight
- Strong wood
- Good dimensional stability
- Workability
- Attractive color and grain pattern
- Excellent versatility
Cons
- Low moisture and water resistant
- Less durable without sealant
- Can quickly rot and decay when prolonged wet
- Low resistance to insect and pests attacks
How to Finish Birch for Outdoor Use
Applying a good finish to your birch increases its characteristics, such as weather resistance from harsh elements. However, it is one of the most durable woods to finish because of its diffuse-porous wood fiber.
In this case, applying a marine spar varnish will keep it protected and in good condition. You must apply this varnish across the surface, including the crevices and legs of the furniture, which traps some moisture.
You should repeat this application once a year, particularly if the furniture is exposed directly to sunlight. Ultraviolet rays break down varnish over time.
How to Finish Birch Plywood for Exterior Use
Step #1: Checking the Stain Color
Test the stain color on a small hidden spot of the baltic birch plywood. Let it dry to reveal the result of your preferred stain. Often, wood reacts to stains based on what you use. It could be lighter or darker color output. Then you can finally decide which finish you are going to use.
Step #2: Sanding the Wood
Get the 220-grit sandpaper and sanding block to smoothen your baltic birch plywood. Ensure to eliminate the impurities such as dirt, debris, and oil, which can be visible after staining.
Birchwood has diffuse-porous with medium pores, so you must sand it to absorb the stain consistently and evenly. After sanding, remove the sand dust using a tack cloth so no residues will be trapped in your stains.
Step #3: Applying the Pre-Stain
After sanding, apply pre-stain on your baltic birch plywood. Pre-stain offers your wood to glue properly for your finishing product. It also prevents blotchy surfaces because of the uneven distribution of stains on your birch furniture.
Step #4: Applying the Stain
Using a sponge or paintbrush, apply the stains along with the direction of the wood grain of your baltic birch plywood. Start from one end of the wood until you reach the other without pausing. Otherwise, you will get a streak or feathering edge.
After you cover all the surfaces, let it dry. You can check the label on the container for appropriate drying and curing time.
Step #5: Applying the Second Stain Layer
Once the first coating is completely dried, apply the second layer. Then let it dry before applying the third coating, but only if the desired result has not been achieved.
Step #6: Sealing
After properly curing the stain, seal the baltic birch plywood using a quality sealer. We recommend using a waterproof seal so the wood will have an additional protective layer against water, moisture, and insect attacks. Unsealed baltic birch plywood could result in deformation.
Make Your Birch Plywood Waterproof in 3 Ways
Painting
Painting plywood is a popular method to keep it waterproof. You can use epoxy paints or water-based acrylic latex paints for your birch plywood but apply a primer as the base of your paint.
Primer reduces the coat you need to apply but offers your paint a better bond to your birch plywood. You can purchase a primer, and an overcoat needed for outdoor plywood, but it would be slightly more expensive than a regular primer and a coat.
Epoxy Sealing
Epoxy sealing makes baltic birch plywood waterproof better than any sealers. Apply a layer of epoxy resin to the surface, creating a barrier between the birch plywood and the harsh elements.
While it offers excellent waterproofing for the wood, it emphasizes the natural color of your birch wood. You can also rely on epoxy sealants for an additional protective layer to your plywood.
Applying Oils
To keep your outdoor birch plywood waterproofed and at the same time improve the natural appearance of birch plywood, you can use Tung oil instead.
This oil offers a typically clear coat while adding a waterproof layer to your wood, unlike linseed oil which changes the appearance of birch plywood while staining.
However, applying oil requires periodic application to ensure excellent waterproofing because oil quickly dries after exposure to various elements.
What Is Birch Best Used For?
In addition to furniture, birch wood has the durability that can be used for many woodworking projects. You can use it for cabinets, flooring, veneer, plywood, toys, kitchen fittings, and wood carving projects.
Better Wood Alternatives for Outdoor Use
Birchwood is an excellent wood for outdoors with proper sealing. Otherwise, consider using other plywood alternatives, such as marine plywood, medium-density overlay, or pressure-treated plywood.
For better wood alternatives for outdoor applications, here is our list of woods with excellent water, moisture, and heat resistance:
- Acacia
- Alder
- Cedar
- Ipe
- Locust
- Mahogany
- Maple
- Oak
- Redwood
- Teak
How Long Does Untreated Plywood Last Outside?
Untreated plywood has at least a two to five years lifespan for outdoor use. This is mainly because untreated plywood is considered bare wood, even though it is composed of many veneer sheets and waterproof glue.
If used outdoors without finish or untreated, plywood would be exposed to external elements such as ultraviolet rays from sunlight and trapped water inside the plywood sheet.
Once the plywood starts deteriorating, you can see its layer bowed and cupped. Then the wood warped, resulting in splitting and delamination, and because of this, you need to replace it after five years at most.
FAQ
Will the exposure to sunlight affect Birch wood when placed outdoors?
The yellow or reddish-brown color of birch becomes gray after exposure to sunlight. Too much exposure from direct sunlight breaks down the cellulose or the top layer of birch wood. And without proper sealant, paint, or stain, the surface is prone to harsh elements such as UV rays.
Conclusion
Undoubtedly, birch is good for outdoors. Its low resistivity from water and heat won’t be a dilemma in woodworking as long as you follow our experts’ methods for waterproofing birch. It will keep your birch plywood and other birchwood projects in good condition.
Most importantly, you can maximize birch plywood with proper wood finishing. But you can always opt for better wood alternatives such as mahogany, walnut, among others, depending on the extent of your woodwork.
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