How to Treat Wood for Outdoor Use – A Comprehensive Guide

Wood is probably the most used material for building and crafting in the history of humanity. And with good reason. It is quite easy to work with, you can get it pretty much anywhere, it is robust but soft enough to easily work with at the same time, and so much more. But there are only a handful of wood types, that can survive the elements outdoors without any treatment. So in this article, I will tell you exactly how you can treat almost any type of wood for outdoor use.

In short, the best ways to treat wood for outdoor use are either using a wood sealer, varnish, or an oil finish. What kind of treatment to use completely depends on the project and the kind of wood that is supposed to be treated.

There is only a very small amount of wood types, that can be put outdoors without any treatment and withstand the elements. These types of woods include Cedarwood and Redwood.

But these kinds of wood can be very expensive, depending on where in the world you live in. So, naturally, you want an alternative that is cheaper but still doesn´t rot when it is outdoors. Luckily we humans have found various ways to seal the wood and protect it from rain, snow, bugs, and everything else, that could possibly harm it.

You could also use pressure treated wood for your project. This kind of wood has been pretreated with chemicals to make it permanently resistant against the elements and bugs of any type. So if you don´t want to coat the wood by hand, then this would be the best alternative. But pressure treated wood is kind of hard to paint, so keep that in mind.

The 3 Best Ways to Treat Wood for Outdoor Use

There are a lot of ways to treat wood to protect it from the elements. You could go the absolute traditional route and fire the wood to seal it just like the Japanese did in medieval times. You could also coat your wood in natural resin just like the Vikings did centuries ago.

But let´s face it, even though these methods sound amazing, you probably want to use a simpler and less spectacular option to treat your wood for outside use. So I only listed the four best and most widely used methods instead of every single possible option. So let´s get to it.

Use Varnish to Treat Wood

Probably my favorite way of treating wood for outdoors is using varnishes.

Other than most other sealers and oils out there, varnishes will not soak into the wood but instead create a watertight coating on top of it.

You can use multiple layers of varnish without any issues. It is actually even recommended to coat every piece of wood in at least two layers of varnish.

The varnish will create a hard outside layer, that will sit on top of the wood, instead of being absorbed by the wood. The advantage of that is, that wood, that has been treated with varnish, can easily be cleaned with water and dirt won´t stick to it at all.

The disadvantage of using varnish is, that you will lose the feel of the wood. What I mean by that is, that the coat of varnish is sitting on top of the wood creating a strong seal. So when you touch the wood all that you will feel is the varnish. It will not feel like wood anymore.

You can get varnish in matt, satin and glossy.

I would recommend using varnishes mainly on wooden tables and chairs but you can use it on anything made out of wood.

How to Use Varnish

  • First, you have to clean the wood, that you want to coat with varnish, from dust and dirt. I usually simply use some soapy water and a sponge to clean the wood.
  • Lightly sand the wood with some fine-grit sandpaper or something similar.
    Learn more about alternative ways to smooth wood without using sandpaper.
  • Clean the wood from any dust and other remains from the sanding process.
  • Apply your varnish with a soft brush. Brush against and with the grain.
  • Let the varnish dry for about 24 hours. Depending on your particular brand the drying time can vary so check the label for an accurate time.

You can add multiple coats if the first coat wasn´t enough or if you want more protection.

Normally at least two coats of varnish are recommended.

Use Wood Sealers to Seal the Wood

Using a wood sealer is probably the easiest and most often used method of treating wood for outdoors.

They are easy to apply, quite cheap compared to other methods, and they will hold for a long time (usually at least two years). You can easily reapply them at any time.

The only real disadvantage of sealing wood with a wood sealer is, that softer woods tend to absorb quite a lot of the sealer. So you might end up using a lot of it to seal softer wood, which could end up being more expensive than you originally planned.

How to Apply Wood Sealers

  • First, you have to clean the wood surface from dust and dirt, as always.
  • Then you have to lightly sand the wood and clean it again before you can apply the sealer.
  • Apply the Sealer to the wood. You can be very generous here, the wood will absorb the sealer quite quickly. Use a brush to spread the sealer but make sure not to leave any drops or streaks on the wood. You will see them very clearly once the sealer has dried so try to spread the sealer evenly to avoid that from happening.
  • Let the sealer dry for at least 24 hours. As always check the label for further information about the exact drying time.

You can repeat the process as often as you like to add more layers to the wood. I would recommend adding at least two layers of the wood sealer for a nice finish.

Use an Oil Finish to Protect the Wood

And the final method is using oil finishes to treat your wood.

This method of sealing wood is the oldest one from all of the ones I mentioned above. Oil was already used in medieval times to keep wood from rotting and to protect it from the elements.

This kind of finish can look really great on wood, which has a beautiful rich grain on it.

But I wouldn´t recommend it if you are not a fan of the natural wood look.

Oils, much like wood sealers, soak into the surface of the wood. They will make the wood water-resistant, a little bit like varnish but without the coating.

How to Apply Oil to Wood

  • As always, clean the surface of the wood from dust and dirt. I usually use some soapy water and a sponge to do so.
  • Apply the first layer of oil with a soft brush. Try to spread the oil as evenly as possible.
  • Let the oil dry for a few hours. The drying time can vary greatly from product to product so read the product label for a drying time estimate.
  • Sometimes the oil will not soak into the wood completely and sit on top of the applied layer. Simply use a piece of cloth to remove any access oil from the surface.

If you are not happy with the first layer or if you want to add additional layers for a better seal then simply repeat the steps. But sand the surface lightly before you do or your next layer will simply sit on top of the od one without soaking into the wood.

When Should I Use Which Method?

There really isn´t a definitive answer to what kind of method is the best for treating wood because it completely depends on the project and what kind of wood you use.

If you are dealing with a very soft kind of wood, then I would recommend using varnish. Mainly for two reasons.

One, Varnish will not soak into the wood but instead create a coat on top of the wood protecting it from water and also from dents and scratches. Which is great because especially softer wood is prone to getting dents and scratches.

And secondly, softer wood is known to soak up a lot of oil and wood sealer. So it is actually cheaper to seal it with varnish.

If you want to seal a wooden table, then I would recommend using varnish as well.

Just because tables have to be cleaned a lot and it can happen quite often, that liquids are spilled on it. Varnish will give you the best protection against water.

If you want to seal a wood decking, then I would recommend either oil or a wood sealer to treat the wood.

This is mainly because varnish can be quite slippery when wet and the varnish finish can look a little weird on floors at times.

Also, oil can look amazing on darker wood while wood sealer can give some red intent wood a really great finish.

So, as you can see there are a lot of things to keep in mind when choosing the right type of treatment for your projects. But on the other side, there really isn´t anything, that you can do horribly wrong by simply choosing one sealer and simply go with that one.

Each of these methods will seal the wood and protect it from the elements and each of them will work on pretty much any type of wood. So if you really have no idea what kind of treatment to use simply pick one and test it on a spare piece of wood. If you like the outcome then use that one.

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