How to Treat Wood for Outdoor Use

Wood is a commonly used material for outdoor use and crafting most of the items used in indoor settings. Unfortunately, in its natural state, wood cannot withstand outside elements such as harsh weather and insects without any treatment.

It’s advisable to treat wood to protect it from bugs, snow, rain, and other outside elements that could harm it. But how exactly do you treat wood for outdoor use?

The best way to treat wood for outdoor use is to seal untreated wood. Other effective ways include applying oil, wood-treatment chemicals, varnish, or paint to make it resistant to harsh outdoor elements.

The treatment method you choose will depend on the type of wood and the project you want to use it on. This article will share innovative options for treating wood for outdoor use. Read on to learn more.

Can you use unsealed wood outdoors?

You can use unsealed wood outdoors if the upcoming project is for short-term use. Some types of wood are tough and may not need to be treated. White oak, cypress, redwood, and cedar withstand harsh weather for longer periods even when they are not treated.

Otherwise, using untreated wood for long-term projects poses several potential issues such as wood decay, fungal growth, and UV light damage.

Therefore, protective measures such as sealing, vanishing, painting, or oiling the wood can help increase the lifespan of untreated wood.

How to treat wood for outdoor use

This section explains different ways you can treat wood for outdoor use.

1. Applying a sealant

Sealing untreated wood is one of the best methods of treating wood for outdoor use. The use of sealants makes unfinished wood impermeable and durable. They work by sealing up the wood’s surface, preventing it from absorbing moisture from the environment and soaking up water from the surrounding.

Once the wood is sealed, the internal structure of the wood remains intact. The wood is not only protected from harsh weather environments but also preserves its original shape during the winter and summer seasons. Below are steps for applying a sealant on the wood:

  • Before you apply your sealant, sand the surface to eliminate any defects and make it smooth. A high-grit paper can help you achieve a smooth and clean surface.
  • The next step is to choose a preferred sealer for the wood you want to seal. There are several brands on the market, so you will need to consider factors such as the type of wood, the condition of the wood, and the outdoor elements you want to protect the wood against.
  • Apply the first coat of the wood sealer using a sprayer or paintbrush. Make sure you apply the sealer evenly and neatly.
  • Leave the wood in the sun to dry for 5 to 8 after applying the first coat.
  • Re-sand the wood you applied the first coat to remove any extra sand. Use low-grit sandpaper when re-sanding the wood.
  • Apply the second layer of sealer and leave the wood to dry for 24 hours.

If the wood has not achieved the required finish, sand it again, apply the third layer of the sealer and dry it for longer hours.

2. Using varnishes

Another method of treating wood for outdoor use is using vanishes. Vanishes offer protection by creating a hard outside layer without damaging the wood. Unlike most oils and sealants that soak the wood, varnishes don’t penetrate the wood. Instead, they create a waterproof covering that absorbs pressure and keeps moisture and other harsh elements away. Below are some of the steps of applying varnish on the wood:

  • Before considering applying varnish on your wood, choose a day when the environment is not too cold or hot. Avoid hot days because the varnish will dry too fast, leaving a mass of bubbles on the surface. Varnish takes longer to dry in a humid environment.
  • Vacuum the area to remove any dust that might settle on the varnish to interfere with the finished surface.
  • Prepare the wood before you apply the varnish. Preparation may include cleaning the wood using soap and water and sanding it using fine-grit sandpaper to make it smooth.
  • Choose a preferred varnish for the wood you are using. You can choose different types of varnish, including glossy, satin, and matt varnish.
  • Use a soft brush to apply the first coat of varnish to the wood. Make sure you apply the varnish along and against the grain. Leave the wood to dry for about 24 hours.
  • Sand the wood again, this time round using fine sandpaper. Apply another coat of the varnish and let it dry for another 24 hours. If you want a finer finish, you may apply multiple coats if the second one isn’t enough.

Once the wood is dry, it will have a hard outside layer that’s dirt resistant and can be easily cleaned with water.

3. Using tung oil or linseed oil

Tung oil is extracted from the seeds of tung trees, while linseed oil is extracted from flax seeds. These two oils penetrate deep into the grain of the wood, protecting it from changes in humidity, scratches, and any other external pressure.

Unlike sealers, paint, and varnish that lose the feel of the wood, hand-rubbed oil finishes preserve the grain and color of the wood underneath.

Some basics you need to complete the task include linseed or tung oil, mineral salt, polyurethane, high-grit and fine sandpaper, wood stirring stick, bristle paint brush, vacuum cleaner, and a couple of rags.

Here’s how to treat outdoor wood using tung oil or linseed oil:

  •  Vacuum any dust and small particles that might be present on the working surface. If dirt is not removed from the surfaces, it might stick on the wood, creating an ugly finish.
  • Clean the wood using a damp cloth and allow it to dry.
  • Sand the wood smooth using a high-grit sandpaper
  • Mix one part linseed or tung oil, one part mineral salts, and one part mineral salt.
  • Using a wood stirring stick, thoroughly stir the mixture gently but thoroughly.
  • Use a bristle paint brush to apply the mixture to the wood with the grain and leave it for at least 8 hours to dry.
  • Once dry, use fine sandpaper for sanding the wood again before applying a second coat of the oil.
  • After applying the second coat, leave the mixture to soak into the wood for 4 to 5 hours, and then reapply oil to any dry patches.
  • Use the rags to wipe off all excess oil from the wood and leave it to dry for at least 10 hours.

If the wood needs multiple coats to achieve desired results, re-sand the wood before applying additional coats. Allow around 6 to 8 hours drying period before you apply another coat. 

Using a pressure treatment

Another effective way of treating wood for outdoor use is a pressure treatment. This method involves using pressure, hot water, and various preservatives such as copper azole, alkaline copper quaternary, and compounds contacting copper.

These preservatives are added to hot water and thoroughly mixed before they are applied under pressure into the wood’s grains. If done properly, these agents will protect the wood from inside. Below are steps for treating wood for outdoor use through the pressure treatment method:

  • Usually, the process takes place in a cylindrical holding tank. Get the tank ready for the task.
  • Add the wood preservatives into hot water and mix them thoroughly.
  • Arrange the wood in the tank, ensuring enough space between different pieces.
  • Poor the mixture of hot water and wood preservatives in the tank.
  • Turn on the pressure tank to introduce pressure to the tank. After a few minutes, the pressure you add will force the wood to soak up the mixture of preservatives.
  • Turn off the tank, remove the cover, remove the wood from the tank and take them into the kiln to dry.

One of the advantages of pressure treatment is the costs associated with this process. You will have to incur the cost of buying a pressurized tank and kiln. However, this might be a good option for large-scale wood treatment.

How long can you preserve wood outdoors?

You won’t be able to preserve untreated wood outdoors for long because its structural integrity can become jeopardized within a few months. The wood may remain usable for a few days but will not survive harsh outdoor elements such as rain, snow, UV sunlight, insects, and bugs.

The exact period the wood can last outside will depend on many factors such as the type of wood, condition of the wood (treated vs. untreated), temperature ranges, humidity, the place of storage (shaded vs. no-shaded area), and how much ground contact it will be subjected to.

For instance, wood such as fir, white oak, cypress, redwood, cedar, and teak can survive untreated outdoors for a long period because they are weather-resistant.

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