Wood is among the most used materials for crafting and building projects. It is robust, easy to handle, and widely available.
In addition, the material is lovely, thanks to its lovely natural wood grain. And it receives various finishes well to deliver a durable project.
Sadly, only a handful of lumber types can survive outdoor elements without treatment. Further, the chosen treatment technique depends on the wood species and the project’s nature.
Therefore, learn the Best Practices for Treating Wood for Outdoor Use to guarantee long-lasting exterior wood pieces.
Apply a paint finish, oil formula, ‘good’ old polyurethane, varnishes, or a stain and sealer combination, depending on the available or preferred option.
Also, you can pressure treat the wood to enhance its natural immunity to elements.
Fortunately, these strategies are easy to execute. You only need to pick what works for your work.
This guide provides more insight into the wood used in outdoor use and how to treat and maintain it for added longevity.
You will also find frequently asked questions by outdoor wood users.
Table of Contents
How to Treat Wood for Outdoor Use
In this section, we will examine various wood treatment techniques. They are proven to keep your wood fresh and looking good despite harsh outdoor conditions.
In addition, each method comes with the recommended application procedure to deliver the best outcome.
Painting the Wood
A paint finish works wonders on your exterior wood pieces.
Besides, although we often do not consider it a protective finish, the product preserves the wood.
Paint hinders moisture exchange between the environment and the lumber, thus, reducing the chances of wood warping, splitting, and checking.
The formula also protects wood from UV deterioration.
Paint is ideal for woodwork like wooden sculptures and fences. It is also convenient to handle and obscures lumber blemishes remarkably.
However, the product is unsuitable if you want to showcase the wood’s properties like grain and figure.
But you can still use paint if you do not mind the inconvenience and get a satisfactory outcome.
The product features a wide color array, giving you options. Only ensure you get an exterior paint that can withstand outdoor elements.
Moreover, you can apply paint with other finishes. For example, feel free to add a polyurethane layer to the painted surface.
This way, you keep the surface waterproof and protect the finish.
Below is a simple procedure for painting outdoor wood.
- Step 1: Check the Wood for Blemishes
Assess the wood for small decay areas and saturate them with lumber preservatives. Then, treat the surface with a wood hardener.
Allow the wood to cure and add a wood filler.
Smooth the surface with abrasive paper. However, ensure you conserve as much original lumber as possible.
- Step 2: Get the Needed Supplies
You will need paintbrushes, a scraper, wet and dry abrasive paper, a nail set, putty, sugar soap, and heavy-duty rubber gloves.
In addition, get a wood primer, an oil-based primer, and exterior wood paint, preferably oil-based.
- Step 3: Remove Old Paint
Scrape away flaking and loose paint from the wood to deliver an appropriate substrate for the new finish.
Use a chemical paint stripper for stubborn paint finishes.
However, ensure you neutralize the compound thoroughly to avoid ruining the new outdoor paintwork.
- Step 4: Create a Key for the Paint
It is advisable to dull shiny paint to deliver a perfect key for new paint. So, rub the surface with coarse abrasive paper.
Next, use wet paper to avoid dusty conditions.
You can also use 150-grit sandpaper. The goal is to roughen the surface, allowing even primer and paint absorption.
- Step 5: Apply the Primer
Prime the surface with the oil primer and let it dry before adding the paint coat.
The primer ensures better adhesion and protects the wood from unfavorable weather conditions.
As a result, it increases the paint job’s durability.
- Step 6: Apply the First Paint Coat
Use a paintbrush, foam brush, roller, or sprayer to apply the formula. Your applicant choice depends on the project’s nature and duration.
For instance, consider a sprayer when working with extensive wood pieces. It delivers impressive coverage within a short duration.
On the other hand, a paintbrush gives the best result for complex and intricate paint projects.
- Step 7: Apply Subsequent Paint Coats
Let the first paint layer dry for four to six hours before adding other coats.
You can have more than two coats, depending on the intended finish. Assess the surface after each application to determine if you need an additional layer.
Polyurethane is hands down an excellent finish for outdoor wood projects. It seals the lumber, blocks its pores, and prevents moisture penetration.
You can use the formula with a Stain to deliver ultimate protection from Ultraviolet rays.
However, polyurethane is more challenging to handle than paint. So, check out the following application procedure.
- Step 1: Get the Recommended Tools and Materials
The project supplies include:
- Sanding block
- Shop vacuum
- Wet/dry sandpaper
- Tack cloth,
- Oil-based polyurethane,
- Mineral spirits,
- Lint-free cloth
- Automotive polishing product
- Automotive rubbing compound
Experts recommend an oil-based formula as it delivers a richer color. In addition, it guarantees superior protection from water and sun damage.
- Step 2: Sand the Wood
Rub the surface with progressively fine sandpaper grits. Most applications need an initial sanding with 100-grit, followed by 150 grits.
Then an extra-fine sanding paper with 220-grit.
The accessory with a higher grit removes the deeper scratches left by the lower-numbered one.
- Step 3: Remove Dust and Debris
Remove the dust once the lumber is blemish-free.
Use a shop vacuum featuring a soft brush attachment. Then, wipe the surface with a clean, lint-free rag moistened with mineral spirits.
- Step 4: Seal the Lumber
Thin the oil-based polyurethane with one part mineral spirits and two parts polyurethane.
Next, brush on the mixture with a natural-bristle paintbrush. And use long, even strokes and catch any runs.
Please avoid shaking the polyurethane can. Otherwise, you’ll introduce bubbles into the solutions, leading to a rough finish.
Always keep a wet edge during application. In addition, overlap each pass until you cover the entire surface.
Lastly, catch drips with the brush and smooth them into the wood.
- Step 5: Apply the First Polyurethane Coat
Brush on a polyurethane layer within 24 hours of applying the sealer. Spread the formula using long, even strokes.
However, do not use too much formula to avoid streaks and rubs. Only use enough.
As a result, you’ll deliver an excellent, uniform coat without dry spots.
- Step 6: Shave off the Bumps
Assess the finish for bumps and drips. Then, cut them away with a razor blade.
However, ensure the wood dries to the touch before this step. And be careful not to cut below the surrounding area.
- Step 7: Wet Sand the First Layer
Ensure the coat is dry to the touch after 24 hours. Next, remove minor surface flaws by wet sanding with 400-grit paper.
Dampen the sandpaper with water. Then, use circular strokes to eliminate blemishes and dust bumps.
Use enough moisture to lubricate the paper. Otherwise, you risk burning through the delicate finish.
Once the lumber feels smooth, wipe it with a damp rag and then dry it.
- Step 8: Apply the Second Polyurethane Coat
Wait 24 to 48 hours to give the first coat enough drying time. Afterward, apply the second layer using the same procedure as the first.
Let the surface dry and assess whether you need a third coat.
Treating Outdoor Wood with a Sealant
This method is among the simplest for treating outdoor wood. Besides, a sealer ensures the lumber is impermeable and durable.
So, the wood remains immune to weather changes. In addition, it does not absorb moisture, preventing decomposition.
Here is a step-by-step application guide.
- Prepare the lumber by cleaning and sanding. This way, you remove blemishes and previous treatment.
- Choose the best sealer for your project.
Consider the product’s quality and the project’s needs. For instance, get marine wood sealant for outdoor wood.
- Apply the first sealer coat using a sprayer or a paintbrush. In addition, ensure complete coverage to guarantee a professional look.
- Let the first coat dry for ten hours before adding the second. And sand it gently to improve adhesion.
- Wipe the lumber with a clean, dry rag to remove dust and debris.
- Apply the second coat and let it dry for some hours. Further, this may need more time to cure, usually ten hours.
- Sand the surface again and add a third layer. Then, allow it to cure for about four days before resuming use.
Here’s How to Seal Outdoor Wood:
This technique involves using pressure, hot water, and various preservatives. Further, the treatment plant infuses hot water with preservatives into the lumber’s grain.
As a result, the wood’s internal part becomes resistant to rotting. Typical preservatives include copper azole, alkaline copper quaternary, and other copper compounds.
Remember, copper is weathering resistant and thus preserves the wood. Moreover, you can buy treated wood if you do not intend to treat it at home.
Although treated timber looks wet, do not panic. The water eventually evaporates, leaving the chemicals behind.
Lastly, add a varnish coat to outdoor wood to protect it from harmful elements.
Applying a Wood Varnish
Unlike most wood formulas, varnishes do not penetrate the lumber. Instead, they create a waterproof covering with inbuilt layers.
As a result, you get a rugged exterior layer.
This covering is a protective shell that keeps moisture at bay and absorbs pressure without damaging the wood.
We can say that varnish is a paint finish stripped of its color.
Further, acrylic varnishes are famous among woodworkers due to their health and environmental benefits.
Generally, you will find three primary varnish types: varnish oils, thinner, and resin.
Also, the oil to resin oil affects the finish, but flatting chemicals help to eliminate unwanted sheen.
Lastly, most varnishes are transparent. Thus, apply a stain before the varnish if you want some color.
So, how do you apply the formula to wood?
- Vacuum the surface to remove dirt and debris.
- Select a fair and humid day, as the varnish dries slower in cold or wet conditions. Further, dirt and dust may accumulate on the surface during drying, compromising the final finish.
- Remove existing varnish or finish using the recommended paint and varnish stripper/remover.
- Sand the lumber to eliminate defects. Then, wipe it with a damp rag.
- Apply the first pure coat varnish and let it dry thoroughly. Next, sand the surface gently with fine sandpaper.
- Add as many coats as possible, usually two to three. Also, the more coats you apply, the deeper the finish. Only ensure you sand before adding the next one.
Treating the Wood with a Stain-Sealer Combo
Simultaneously use different manufacturers to mix stain and sealer in a single package. It saves you from deciding between a sealer and a stain.
Besides, the product is more economical if you want to stain and seal the surface.
A stain and sealer combination delivers a coloring and sealing product. In addition, this treatment looks perfect on light-colored surfaces.
Conversely, polyurethane-based finishes are prone to fading and yellowing, making the lumber appear older.
A stain and sealer combination ensures the wood is dark enough to hide this defect.
Also, applying the formula uses the same product as sealing the wood. Just give it more drying time.
In addition, you may need more steps to prepare the surface.
Thus, read the manufacturer’s instructions carefully before handling the product.
Below is a summarized procedure.
- Apply the formula evenly and fast using a clean brush. Also, follow the wood grain to facilitate a uniform look.
- Check for even coverage, paying attention to end grain areas. Unsealed end grain soaks more formula than other wood areas.
- Give the thinned white Shellac two hours to dry and one hour for industrial sanding formula.
- Softly sand the wood with fine-grit paper.
- Remove remaining debris with a tack cloth.
- Ensure the first layer dries thoroughly before adding subsequent ones.
Applying an Oil Finish
An exterior oil formula is the most straightforward way to treat outdoor wood. But it only protects the surface from outdoor elements for about a year.
Also, unlike varnish, oil finishes do not sit on the surface to deliver a protective layer. Instead, they penetrate the wood fibers and dry.
Exterior oils have trans-oxide pigments that protect the wood from UV rays, mold, and mildew.
Even better, the formula comes in multiple colors ranging from light amber to dark brown.
The application procedure is as follows:
- Coat the wood with oil using a garden sprayer with a hand pump. It makes the process quick and easy.
- Allow the formula to penetrate the wood according to the manufacturer’s instructions.
- Renew the finish annually, depending on local conditions. The built-in UV protection keeps the lumber natural with periodic reapplication.
What Is the Difference Between Wood Protector and Wood Preserver?
Generally, there is a minimal difference between wood protectors and wood preservers. Some manufacturers use the terms interchangeably.
In such a case, the difference between the formulas is whether one is water-based or solvent-based.
Thus, it is best to check the product description if it says, protector or preserver.
As a rule of thumb, lumber protectors work well on pre-treated surfaces. They offer protection against deterioration, environmental damage, and decay.
On the other hand, wood preservers offer protection against fungal decay and lumber-boring insects.
Wood protectors, like most paint, can either be water-based or solvent-based. Further, they have benefits and drawbacks, depending on the project requirements.
Both options have similar protecting ingredients. But a solvent-based formula has better penetration abilities.
Also, it is more water-repellent and protects the wood from moisture damage.
Conversely, a water-based protector is easier to handle and eco-friendly.
Usually, wood protectors and preservers are transparent, only darkening the lumber’s natural hue.
But you can still get some with different colors. They dye the wood while protecting it.
A wood preserver is an undercoat. You spray or brush it onto sanded or raw and freshly sawn wood surfaces.
The formula also stabilizes the lumber’s moisture content, making it rot and decay-resistant.
What Are the Three Types of Wood Preservatives?
Usually, wood preservatives are the primary ingredient during chemical wood treatment.
Further, the process requires the compounds to be infused in lumber at very high-pressure levels.
Thus, most woodworkers prefer to buy already treated wood rather than treat it themselves.
These wood preservatives include:
CA preservatives contain copper, chromium, and arsenic. Since the 1940s, treating plants have used these compounds to protect the lumber from rotting.
Further, they discourage insect and microbial agent attacks and wood-boring marine invertebrates.
Most woodworkers used chromate arsenic-treated wood from the 70s to the 2000s in outdoor residential applications.
However, effective December 31, 2003, chromate arsenic-treating plants voluntarily stopped using CCA-treated products.
In addition, EPA classifies chromate arsenicals as restricted-use products only for use by certified pesticide applicators.
CCA-treated wood works well for commercial wood posts, poles, shingles, shakes, pilings, permanent foundation support beams, and other approved lumber products.
Creosote is a heavy-duty lumber preservative. It comes from distilling coal tar under high-temperature.
Pesticides with creosote as an active ingredient protect lumber against fungi, mites, termites, and other wood-degrading pests.
Currently, creosote is only used for commercial purposes. It has no approved or registered residential uses.
Further, the authorities do not allow using creosote for indoor projects or surfaces in contact with feed, food, or drinking water.
However, you can use it in outdoor settings such as utility poles and railroad ties.
PCP became a registered pesticide on December 1, 1950. Further, it was a famous biocide in the US before 1987.
However, the authorities disapproved of the product’s uses as a defoliant, herbicide, and disinfectant.
Currently, Pentachlorophenol has no registered residential purposes. It is a restricted use pesticide only allowed for commercial purposes.
Alternative Wood Preservatives
This wood preservative is a triazole fungicide first registered in 2009.
Triademefom became EPA-approved for preserving wood-based products for in-ground contact.
It is also ideal for above-groundwork, such as patio furniture, millwork, wood decking, utility poles, fences, guardrails, and foundation pilings.
This chemical is also a triazole fungicide, registered in 1981.
Further, it is EPA approved for preserving lumber used in shingles, shakes, millwork, siding, structural wood, plywood, and composites used in above-ground applications.
But Propiconazole, by itself, does not protect lumber against insect damage. You have to use it with other chemicals.
- Acid Copper Chromate (ACC)
ACC wood preservative is only registered for commercial and industrial uses.
Moreover, the Chromated Arsenicals registration review case reevaluates the compound frequently to confirm it is fit for use.
This wood preservatives class contains three primary chemicals.
The most common compound is DCOIT (3(2H)-isothiazolinone, 4,5-dichloro-2-octyl), registered in 1996.
It is suitable for sap stain protection, millwork projects, and utility poles.
OIT (2-n-octyl-4-isothiazolin-3-one) is the next chemical. It is also an excellent sap stain wood preservative.
Lastly, we have a mixture of the isothiazolinone MIT (2-methyl-4-isothiazolinone-3-one) and CMIT (5-chloro-2-methyl-4-isothiazolinone-3-one).
The solution is a primary ingredient in wood pressure treatment.
Newer Wood Preservatives for Residential Uses
Recently, EPA registered new wood preservative active compounds.
Furthermore, these products have lower toxicity profiles, making them suitable for commercial and residential uses.
The chemicals include:
This compound is EPA approved as a water-based preservative.
Moreover, government agencies in Europe, Asia, and North America endorse it for various woodworking tasks.
Typical applications include interior and furnishings construction such as sill plates, sheathing, trusses, furring strips, framing, and joists.
- Alkaline Copper Quaternary
ACQ is a water-based lumber preservative preventing insect attacks and fungi decay.
In addition, it features relatively low risks based on its quaternary ammonium and copper oxide compounds.
Water-based chemicals like ACQ deliver a dry, paintable surface.
Moreover, you can use it on timbers, fence posts, utility poles, freshwater and marine pilings, decking, sea walls, wood shingles, and landscape ties.
- Copper Naphthenate
Copper Naphthenate, first registered in 1951, brushes, sprays, dips, and pressure treats lumber.
As a result, the treated wood works best for water contact, ground contact, and above-ground use, such as docks, posts, fences, piers, utility poles, and landscape projects.
Copper Naphthenate also protects lumber pieces against insect damage.
- Copper- HDO (Bis-(Ncyclohexyldiazeniumdioxy- copper))
Copper- HDO, first registered in 2005, treats lumber used as rails, frames, sills plates, fences, spindles, decks, gazebos, and posts.
However, the authorities restrict it from use in beehive construction, marine areas, or applications associated with food or feed packaging.
- Copper Azole
This water-based lumber chemical prevents insect attacks and fungal decay. Hence, it is a perfect insecticide and fungicide.
Copper Azole leaves the wood with a clean, paintable surface.
Also, you can use it to treat wood used for shingles, siding, plywood, millwork, structural lumber, building and utility poles, composites, and fence posts.
Finally, copper Azole-treated materials are perfect for ground contact and above-ground, fresh water, and salty water decking applications.
- Polymeric Betaine
The United States first registered Polymeric Betaine as an active ingredient in 2006.
Further, after infusion, the compound breaks down to boric acid and didecyl dimethyl ammonium chloride (DDAC).
How Long Does Untreated Wood Last Outside?
Untreated wood lasts a few months to two years without a protective coating.
Some wood types last for years when left outside without treatment, while others rot within a few months.
For instance, redwood, cedar, white oak, and Cypress survive long durations left untreated, whereas alder, white oak, and hemlock quickly fail if they stay outdoors without treatment.
However, we do not have a hard and fast rule for this duration.
The longevity depends on the wood type and exposure level to harsh climatic elements like heat, rain, sun, and humidity.
Also, how you cut the wood grain significantly affects the untreated wood’s life expectancy.
The lumber’s water content and the presence and prevalence of fungus and bacteria compromise its life span.
Similarly, exposure to rodents, insects, and ground contact impacts the wood’s usefulness.
Therefore, ensure you take protective measures to protect and keep lumber workpieces healthy.
For example, always keep the material dry during the most humid seasons. Use a large outdoor fan or regularly clean the lumber with a dry rag.
Also, consider waterproofing the surface.
You can use tung or linseed oil to repel moisture while delivering a lovely finish. Or apply a varnish, lacquer, or polyurethane sealer.
Alternatively, finish the wood with a stain-sealant combination.
Importance of Treating Wood for Outdoor Use
Dry wood with less than 20 percent humidity is less likely to rot. But unfortunately, this scenario is not practical for outdoor use.
So, treat the wood to enhance its efficacy in exterior applications.
The importance of the exercise is as follows.
Treated lumber features a longer life span than untreated wood.
In addition, the treatment process infuses preservatives in the wood. These compounds prevent fungi and repel insects, which often rot the lumber.
Other treatment strategies add a protective finish to the wood, making it water-resistant.
Prolonged Immersion in Water
Treated plywood is perfect for shipbuilding.
It resists corrosion from seawater, delivering incredible longevity to the project despite excess water exposure.
Treating wood protects it from harsh weather elements such as rain, snow, and sunlight.
The process also preserves the wood against fire.
Some treated lumber types are flame retardant, which slows down the combustion process and increases the burning time.
Further, fire retardant wood comes in handy for restaurants and homes.
Treated lumber is versatile and excellent for multiple construction projects.
In addition, we have various wood treatment methods to accommodate different project needs.
Frequently Asked Questions
Some of the most asked questions include:
Why Treat Wood for Outdoor Use?
The sun is among the leading causes of damage to exterior wood. It releases UV rays that deplete the lumber’s natural oils.
Ultimately, the material becomes dry, discolored, and disfigured.
Further, rain, snow, and humidity often damage untreated wood because of its porous surface is porous.
Excess moisture also causes mold and fungi growth, eventually causing further damage.
Also, drastic temperature changes alter the wood’s moisture content, leading to expansion and shrinkage.
What Is the Best Treatment for Exterior Wood?
We have two strategies to guarantee your exterior wood’s long-life protection against wear, rot, and decay.
First, consider oil-based products soaking into the lumber’s surface. They penetrate and cure inside the material, thus hardening the grain.
As a result, the wood remains rugged and weather-resistant while maintaining its texture.
Also, you can use a protective finish to deliver superior protection from cracking, flaking, and peeling.
Varnish and Shellac are better choices as they dry quickly on the wood.
How Do I Use Untreated Wood Outdoors?
The first step is to ensure the wood remains as dry as possible. In addition, please minimize sunlight exposure to prevent long-term damage.
Also, keeping the wood under the shade without direct sun exposure makes a significant difference.
So, bring outdoor furniture indoors when not in use to prevent unnecessary exposure to the elements.
Finally, always ensure that the lumber species can resist inclement environmental conditions when choosing outdoor furniture.
What Is the Longest-Lasting Wood for Outdoor Use?
Prolonged exposure to natural elements ultimately leads to wood damage.
However, this aspect does not hinder you from using untreated lumber in outdoor applications.
Moreover, choosing the right untreated wood type helps ensure your project lasts longer.
Several lumber species have naturally occurring chemicals that help resist natural elements and insects.
This tree species is famous for its natural beauty and aromatic smell. Besides, it can naturally resist natural decay via moisture and insect.
Cedar is widely available and best for decking, fencing, and trim, thanks to its dimensional stability and straight grain.
Redwood is a favorite among woodworkers due to its unique reddish hue.
In addition, it has incredible integrity and naturally occurring chemicals that resist the elements.
However, redwood is not readily available.
Due to the lumber’s decreased population, we have strict regulations protecting larger and older Redwood trees.
This lumber type is another alternative for outdoor wood. It has a lovely yellow to reddish-brown color.
Further, Cypress is stable and does not split easily, thus useful for various applications.
Although the wood is relatively resistant to decay, it is not naturally insect resistant.
Also, Cypress does not come close to Cedar and Redwood’s organic preservative qualities. As a result, it works best in hot and dry climates.
Previously, teak was the go-to lumber type for boat-building in most cultures worldwide. It does not crack easily under pressure.
In addition, unlike other wood species, teakwood does not become black when used with metal.
Teak features a naturally high oil level, making it resistant to rot, moisture, and decay.
Thus, it features incredible longevity and durability when confronted with harsh climatic conditions.
Teakwood also naturally resists termites and other wood-eating insects.
But the lumber type is not widely available because of decades of overharvesting. So, it is more expensive than other lumber options.
Do I Need a Wood Preservative for Outdoor Lumber?
It is advisable to use wood preservatives on outdoor wood to guarantee longevity.
The products control wood degradation problems due to decay, mold, sap stain, fungal rot, or wood-destroying insects.
Remember, lumber is hard-wearing and versatile hence perfect for various outdoor projects.
More specifically, you can comfortably use the material for decking, garden furniture, fences, sheds, and cabins.
But please note that wood is susceptible to insect and moisture damage. Even worse, it succumbs to common deterioration culprits like mold, fungi, and algae.
These organisms are prevalent in damp areas and cause early wood rot.
Even worse, wet conditions make the wood sag and misshape, compromising its structural integrity.
Fortunately, while we cannot control the environment or the weather, it is possible to protect the wood using preservatives.
Can I Use Other Products Over Preservers or Protectors?
You can finish over preservers and protectors. But please check what the specific protector or preserver recommends about top coats.
Also, some protectors and preservers have some color tint, while some are like a stain and accentuate the wood grain.
It boils down to what you want. Only ensure that the top coat delivers complete coverage.
Further, an oil-based wood protector does not accommodate a water-based top coat. But you can add an oil-based top coat on a water-based protector.
Lastly, the protector or preserver will repel water-based top coats if it has wax ingredients.
Outdoor wood suffers a higher damage risk from environmental elements than indoor lumber.
As such, it needs special treatment to survive in exterior conditions.
Furthermore, although we have other materials woodworkers can use for outdoor work, wood’s unique appearance is difficult to replicate.
Therefore, experts have sought strategies to make the product efficient for exterior applications. Check out the above discussion on:
How to Treat Wood for Outdoor Use
You do not need to be an expert to treat wood for outdoor use.
The first option is to add a topcoat to the surface. It could be paint, a sealer, an oil formula, or a stain sealer combination.
Alternatively, pressure-treat the wood before use. Luckily, most lumberyards sell pre-treated lumber.