Does Pressure Treated Wood Need to Be Sealed?

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pressure treated wood need to be sealed

One of the major benefits of pressure treated wood is that it is fairly durable. 

Pressure treated wood is usually soft like pine and cedar. Because of this, the oils that are injected into it help keep it from splintering. 

Many people think that pressure treated wood will also be protected from water damage. 

While it is usually used for things like decks and outdoor structures, it is not waterproof. Pressure treated wood can still absorb moisture and rain. 

This means that it can grow things like rot and mold over time. 

If you want to avoid this, sealing your pressure treated wood is essential. Knowing how to do this properly can help you protect your outdoor wood surfaces. 

Sealing Pressure Treated Wood: Basic Idea

Sealing pressure treated wood is fairly simple. If you follow the correct steps, you can give yourself the best possible chance at preserving it. 

These steps are: 

  • Choose a sealer 
  • Wash the surface 
  • Sand the wood
  • Apply the sealant 

Why Does Pressure Treated Wood Have to Be Sealed?

why does pressure treated wood have to be sealed

Pressure treated wood is usually very soft and can be susceptible to damage over time. 

Because of this, it gets injected with chemical preservatives that help prevent rot and insect damage. 

It is placed in a high-pressure chamber and the chemicals are forced through the pores. 

While this can help with certain types of damage, it can still get moldy and take on mildew. The chemicals do not close up the pores. 

Because of this, if you plan on using pressure treated wood for outdoor projects, sealing it is best. A sealant will close up the pores and prevent water from getting inside. 

Pick a Sealer

You will need to pick a proper sealer for your pressure treated wood. 

It is best to use a clear, oil-based sealant. Before you do this, this would be the time to stain the surface if you want to change the color. 

The stain will seep into the pores, which will then be closed by the sealant. You can use almost any kind of stain you want since it will be protected by the clear coat. 

Using a sealant with an acrylic finish will give you a durable shine as well. You can keep the look of your deck and make sure it is protected.  

Clean the Wood

Before you put down your sealant, you will want to clean the wood surface thoroughly. Any debris that is on the surface of the wood will get stuck under the sealant. 

Use a pressure washer to completely clean the surface. This is especially effective if you are cleaning a deck. 

Get the entire surface clean and then wait for it to dry. It is recommended that you completely dry the area and wait at least 48 hours before moving on. 

Sand the Surface 

After the surface has been dried, you can then move on to sanding. 

Using a rough-grit sandpaper, thoroughly sand the area you want to seal. After you have made a pass at it, clean the area. 

Make another pass on the surface with a fine-grit sandpaper. Repeat as many times as is necessary to get the area smooth and clean. 

After you have done this, wash the area one more time with the pressure washer. 

Apply the Sealer 

If you are going to stain the surface, this is the time to do it. Apply the stain with cloth and allow it to dry fully before moving on. 

It is recommended that you wait 48 hours for the stain to completely dry. 

After the stain is dry, you can apply the sealer. Use a roller and apply the sealer evenly across the surface. 

Add two to three coats, allowing each coat to thoroughly dry. After you have applied the last coat, let the sealer cure for at least 72 hours before walking on it. 

Frequently Asked Questions

faq pressure treated wood need to be sealed

  • What is the best sealer for pressure treated wood?

The best sealer for pressure treated wood will be oil-based. 

Look for an oil-based sealer that has an acrylic finish. This will give the surface a clean shine and protect it for many years. 

  • Is it better to stain or seal a deck?

It is best to both stain and seal a deck if you want it to have a finished look. 

However, if you can only choose one, it is best to seal it. This will protect the wood and keep it from rotting or splitting. 

  • How long do you wait to waterproof a new deck?

After getting a new deck installed, wait at least 30 days to seal it. 

Oftentimes, wood will be too wet to seal and the sealant will not take. As soon as the wood has dried, you can then apply the sealant. 


Sealing pressure treated wood is a great way to give it the protection it needs. 

If you follow the above steps, you can be sure that your wood surfaces will be protected. By combining pressure treatment and sealing, your deck or structure will last for many years. 

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Michael J. O’Connor is a writer and marketing specialist from the Bay Area of California. A graduate of Sonoma State’s Creative Writing program, he spent many years as a contractor and carpet layer, learning the ins and outs of flooring and general contracting. When he’s not typing away at his desk, he enjoys hiking with his dogs, woodworking and collecting rare books. See full biography here.

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