Last Updated on October 14, 2023 by Ernest Godia
Pine is incredibly popular among woodworkers due to its ubiquity. The wood is also inexpensive and easy to work with, so you can use it in many woodworking applications.
However, pine is one of the least durable wood options for outdoor uses. It lacks the natural adaptation to make it resilient against outdoor weather extremes. Fortunately, you can protect the wood and increase its lifespan significantly.
This is why pressure-treated pine is a more popular outdoor wood than regular pine. Still, knowing how to treat pine for outdoor use can help you protect and use standard pine on exterior applications.
How to treat pine for outdoor use
How to treat pine wood for outdoor use partly depends on the intended application and the weather elements that the wood will be exposed to.
For instance, fences and garden furniture will require treatment to withstand insect attacks and resist the elements, while patio seats can do without resistance to termites. This is because they sit above the ground, often in a sheltered area.
Here are the four main methods for treating pinewood to resist warping, splitting, cracking, or rotting outdoors.
Method 1. Seal it with polyurethane
Polyurethane is among the most durable plastic resins on the market, with an incredible ability to seal pores on wood.
It is available in a wide range of finishes, so you can choose high gloss, semi-gloss, satin, and matte options depending on your preferred level of shine.
You can also choose a water-based or oil-based option. While water-based poly is currently just as durable as oil-based poly, the latter is historically preferred for high-traffic areas due to its superior strength and durability.
Oil-based poly is, however, more toxic than its water-based cousin. But this will not often be a consideration on outdoor projects.
What you will need to seal pine with polyurethane
- Polyurethane (preferably oil-based for outdoor projects)
- Mineral spirits
- Plastic sheeting or drop cloth
- Hand gloves
- Sander and sandpaper
- Safety mask or respirator
How to treat pine with polyurethane for outdoor use
Once you have everything you need for this project, follow the procedure below to seal and protect your wood with polyurethane.
Step 1. Set your workspace in a well-ventilated area
Oil-based polyurethane emits toxic fumes, so you need to work in a well-ventilated space to avoid inhaling air saturated with these fumes.
Lay plastic sheeting or drop cloth to collect any spills or sanding dust produced while you work. Ensure you cover any items that you cannot move away from your workstation to protect them from any spills or wood dust.
Next, wear a safety mask or respirator to protect yourself from inhaling wood dust and the fumes from polyurethane. This is especially important if you are sensitive to strong fumes or pollen.
Step 2. Sand the wood surface
Sanding helps smooth the wood surface and opens the pores to give the polyurethane a better grip.
Use a power sander for a large project, but for a small project, you can use a sanding block. Your choice of sandpaper grit should depend on the project. In any case, most outdoor projects will require starting with coarse-grit sandpaper and finishing with medium grit.
Step 3. Seal the pinewood with diluted polyurethane
Diluted polyurethane acts as a wood conditioner allowing better coverage for your sealant.
Since you are using oil-based polyurethane for your outdoor project, dilute it with mineral spirits in a ratio of 2:1. Saturate a paintbrush with the diluted poly and apply it to the sanded pine surface in long, even strokes.
Check the surface for any runs, and use the paintbrush to even them out if you see any. Ensure you do this before the runs drip off or dry out.
Once done, leave the pine to dry for 24 hours.
Step 4. Coat your wood with undiluted polyurethane
Once the base coat of diluted polyurethane has dried for 24 hours, use a clean paintbrush to apply a coat of undiluted poly over it.
Dip the brush in the polyurethane can and apply the sealer in long, even strokes. Ensure you catch any drips as you go, and keep each coat thin and even.
Cover every inch of the wood’s surface and let the polyurethane dry for another 24 hours before applying additional coats.
Step 5. Recoat the pine surface
After the surface has dried for the recommended duration, add two to three more coats of polyurethane to achieve the desired coverage. Ensure you let the surface dry for 24 hours between each subsequent coat.
We also recommend scuffing the surface with ultra-fine grit sandpaper between coats. Rubbing the surface with fine sandpaper should help the subsequent coat stick better and become more durable.
Step 6. Shave off any bumps on the dried wood surface
After the last coat of polyurethane has dried, inspect the wood surface for any lumps or uneven spots. If any, use a sharp razor to cut them away. This step is only necessary if you missed any drips that have since dried up.
Do not cut deep, as doing so can spoil the layers of polyurethane on your pine. Instead, cut the bumps so that these areas are flush with the rest of the wood surface.
Once done, use a fine 400-grit sandpaper to smoothen the entire surface.
Step 7. Brush on a finishing coat of poly
Once your entire wood surface is free of bumps, and you have scuffed it up, brush on a final coat of poly to give the wood your desired gloss.
Keep the coat as thin and even as possible because you will not rub it again with sandpaper. Instead, check for any imperfections as you go, ensuring you leave none.
Once you finish applying this final coat, let it dry for 24 hours undisturbed.
- You may have to repeat these steps every two to three years to keep the wood adequately protected with polyurethane.
- You can use exterior-grade lacquer or varnish instead of polyurethane. Each of these has its strengths and limitations and will require following the same application procedure as poly above.
Lacquer is a highly durable finish with a glossy sheen. It is typically made by dissolving resin from waxes and trees in alcohol or turpentine.
While the finish is generally glossy, the sheen levels differ from one product to another. And since lacquer has a thinner consistency than polyurethane, you must apply several coats to achieve the desired strength and durability.
Three to five coats of lacquer should create a durable coat, but you can apply more for outdoor projects and high-traffic areas.
The product dries pretty quickly, so you should finish the project in less time than polyurethane.
Varnish is a hard-wearing sealant for wood, metals, and other surfaces. It is made from tree resin, drying oil, and a solvent.
Varnish forms a tough coat on the surfaces like wood, protecting them from moisture and physical damage such as scratches and dents. This happens as the solvent in the product evaporates, leaving the resin to harden into a rock-solid coat.
Varnish can be clear or yellowish and protects against UV rays depending on its color.
Like polyurethane, varnish requires approximately 24 hours to dry, even though some varnishes dry in as little as 6 hours.
Nonetheless, ensure you apply several coats of exterior grade varnish to protect your outdoor pine projects adequately.
Method 2. Use epoxy sealant
Epoxy is another sealant that gives pine wood a bright, clean finish. The product is made of organic compounds and epoxy resins that form a tough coat on the wood surface when dry.
When you protect pine or any wood with epoxy filler, you will need to apply a light coat of varnish or lacquer over it.
Also, like all sealants, ensure you choose a UV-resistant epoxy rated for outdoor use. Not all epoxies are suited for outdoor use.
Here is the list of supplies you will need to seal pine with epoxy.
- Exterior grade wood epoxy
- Lacquer or varnish sealant
- Safety mask or respirator
- Sander and sandpaper
- Tack cloth or vacuum cleaner
- Drop cloth or plastic sheeting
- Applicators (Putty knife and paintbrush)
Once you have all these requirements, follow the following steps to complete the project using wood epoxy.
Preliminary step. Lay a tarp or plastic sheeting and prepare your workspace.
Since you are treating pine for outdoor use, the chances are that you will be working outdoors, which is ideal. But if you work indoors, such as in the garage, ensure you open any windows and the garage door to create a well-ventilated work area.
Cover the floor or ground with a plastic sheeting or tarp to catch any drips or debris created while you work.
You also need to wear a respirator mask before you start handling epoxy if you are sensitive to strong odors.
Step 1. Sand the wood
You can use a sanding sponge to smoothen the wood surface for a small project or a power sander for a large project.
Once the surface is smooth and even, use a shop vac to pick up the sanding dust or tack cloth if the project is a small one, like an outdoor chair.
Step 2. Apply your first coat of wood epoxy
Use a putty knife to scoop the epoxy from its container and apply it to your project. Spread the wood epoxy with the edge of the putty knife along the pinewood surface.
Flatten out any bubbles, bumps, and thick sections the epoxy forms as you go to achieve a thin, even coat. We recommend working in straight lines along the wood grain until you have covered the entire surface.
If the wood has any holes, you can feed the epoxy into them with your hands before flattening the surface with the putty knife.
Once done, let the epoxy coat dry for approximately 24 hours before recoating.
Step 3. Apply additional coats
Once the first coat of wood epoxy is dry, scuff sand the entire surface to smoothen it before applying the second coat.
Ensure you follow the same procedure when recoating as you did the first time.
After covering the entire surface with a thin, even coat of epoxy and flattening out any bumps, thick areas, and bubbles, allow it to dry for another 24 hours.
After the pine has dried, scuff sand it and apply the third coat. We recommend applying two to three coats for the best coverage and a durable finish.
Step 4. Let it cure for four to five days
After applying the final coat of epoxy and achieving the desired coverage, set aside the wooden item to dry for up to five days.
Wood epoxy has a thick consistency and generally takes several days to dry completely. Ensure the object remains completely undisturbed in a sheltered area while drying.
Step 5. Seal it with varnish or lacquer
Once the wood epoxy has fully cured, brush on a thin coat of lacquer or varnish to seal it up. Wood epoxy can have a porous texture, so a coat of lacquer or varnish will help waterproof it.
Ensure you scuff sand the entire surface before applying the varnish with a paintbrush.
Method 3. Paint it with exterior paint
Outdoor paint is an excellent choice if you do not mind losing sight of the wood grain or color. It also allows you to choose the color you want, which can perfectly match the pine object with the rest of your exterior décor.
You can paint outdoor pine tables, chairs, fences, garden boxes, or wooden flower pots.
What you will need
- Can of paint
- Paint primer
- Drop cloth
- Painter’s tape
- Protective personal gear
- Clean rags
How to treat pine by painting
Like many wood finishes, paint can have a strong odor, so we recommend working in a well-ventilated area. Once you have chosen the right spot, lay a drop cloth or plastic sheeting to collect any spills.
Preliminary step: Choose an exterior-grade paint
Exterior paint is formulated to withstand the damaging effects of the sun’s UV rays and other extreme weather elements. So begin by selecting a paint type formulated for use outdoors.
- For pressure-treated pine, choose latex paint.
- For untreated pine, go for oil-based paint instead. This paint type has enhanced moisture resistance and is suitable for outdoor use.
Step 1. Sand the wood
A rough or uneven wood surface will show through the finish, especially a painted surface, due to its bright color and reflective sheen.
Therefore, it is crucial that you sand the wood with medium-grit sandpaper and finally with fine-grit sandpaper to smoothen the surface.
After sanding, wipe the surface with a clean rag dampened with mineral spirits (if using oil-based paint) or water (if using latex paint)
The cloth must not be saturated with water as such will raise the wood grain. And allow it to dry after giving it a thorough wipe-down before proceeding to the next step.
Step 2. Apply a primer
Primer helps the paint adhere better and form a more durable coat. It should be the same base as the paint. So the primer should be water-based if you have latex paint and oil or solvent-based for oil-based paint.
Apply the primer in thin, even coats covering the entire surface. You can use a paintbrush or paint sprayer to apply the primer, depending on the type you are using.
Consider applying one or two thin coats for better coverage. More importantly, allow the primer to dry between coats as the label recommends.
Step 3. Paint it up
Like the primer, you can spray the paint or use a paintbrush or roller to apply it. Whichever applicator you choose, ensure you apply two to three coats of paint, allowing each coat to dry completely before the next.
After painting, allow the surface to dry for the time recommended on the product label.
You can also apply a compatible sealant over the paint, even though this is optional when you use exterior-grade paint. Such paint is formulated to be durable without a sealant.
Method 4 – Use an all-in-one stain-sealant combo
Deck stains are typically available as stain and sealant combos. The products usually consist of a mix of exterior-grade wood stain and polyurethane.
If you are treating a pine deck, a stain-sealant combo like Seal-Once Marine Premium Wood Sealer is an ideal option. It will color your deck while also sealing it against water and other liquids.
The finish is hard-wearing and can be incredibly long-lasting. The finished pine surface can last several years before it requires a do-over.
Alternatively, you can mix stain with polyurethane to create your own DIY stain-sealant combo.
How to apply a stain sealant combo
Step 1: Clean the wood surface thoroughly and let it dry.
Step 2: Sand the wood surface and wipe away the sanding dust
Step 3: Apply the sealant with a paint pad applicator with a long handle and allow it to dry as recommended on the product label.
Ideally, the product should specify how many coats to apply and the drying times. Ensure you pay close attention to these instructions for the best results.
Is It Safe To Use Untreated Pine Outside?
No, using untreated pine outdoors is not safe. Unlike woods like teak, pine is susceptible to the elements and insect damage. If left untreated, pine will not hold up well against the elements and may rot or get damaged quickly.
How weather elements affect untreated pine outdoors
Moisture, precipitation, and rainwater pose the greatest risk to untreated pine outdoors. Water penetrates the wood’s pores, causing decay and a much-reduced lifespan.
Water also breeds molds that discolor the wood and damage its structural integrity.
Sunlight contains harmful ultraviolet rays that cause the wood to fade. The heat from the sun also dries the structural oils that preserve and keep pinewood healthy. This results in cracking, warping, and weakening of the wood.
Humid air contains lots of moisture that affect pinewood in the same way as water. Moist air also causes condensation, with the resulting water ending up on the wood, causing it to rot and damage it.
Maintenance practices for pine wood
- Keep untreated pinewood dry at all times.
- Wipe away spills on untreated wood as soon as they occur, or you become aware of them.
- Keep untreated pine away from humid environments to avoid molds, decay, and rot.
- Keep the wood sheltered from direct sunlight to protect it from UV damage.
- Seal pine wood to make it weatherproof.
How long will pinewood last outside
The lifespan of pinewood outdoors depends on whether it is treated or untreated. Pressure-treated pine has a lifespan of 10 to 15 years outdoors, in contact with the ground. Some treated pine woods last as long as 30 outside.
However, if left untreated, the lifespan of pine is significantly reduced and depends on how exposed it is to the elements.
Can you use non-pressure-treated pine for a deck?
Yes, you can use non-pressure-treated pine for outdoor projects like wooden decks. But you must seal, stain, or paint the wood to protect it from water and UV damage. Pine is not rot-resistant, so leaving it untreated outdoors will significantly reduce its service life.
What is the best way to treat pine wood for outdoor use?
The best way to treat pine for outdoor use is to seal it with an exterior-grade finish such as polyurethane, lacquer, epoxy, and varnish. You can also use a stain-sealant combination or mixture consisting of one part linseed oil or Tung or one part polyurethane and mineral spirits.
Can pine wood be used outside?
Yes, Pine wood can be used on outdoor projects like wooden decks and furniture. However, ensure you seal, stain, or paint the wood to protect it from water and UV damage to last outdoors.
How do you seal pine wood?
You can seal pine wood with clear finishes like polyurethane or varnish like any other wood. Ensure you read the user instructions on the label of your selected product and follow them to the letter for the best results.
How do you prepare untreated wood for outdoor use?
To prepare untreated wood for outdoor use, clean it to remove any dust or debris. Next, sand it to make it smooth, and then apply a wood conditioner with a paintbrush, followed by an outdoor-rated sealer like polyurethane, varnish, lacquer, or stain-sealant combo.
You can also paint the wood with an exterior paint after sanding and coating it with a compatible primer.
How to Treat Pine for Outdoor Use: Recap
Exterior-grade sealants like polyurethane, epoxy, varnish, and paint all treat and preserve pine for outdoor use.
You can use clear sealers like polyurethane and varnish if you wish to preserve the wood’s natural character. However, if you wish to change the color or mark the wood grain, consider painting it or coating it with epoxy.
Whichever product you choose, ensure it is rated for outdoor use and follow the application instructions on the label for the best results.
We hope this detailed guide helps you treat your pine for outdoor use successfully. And share your experience in the comments.