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Does Pressure-Treated Wood Rot?

Pressure-treated wood is extremely long-lasting and easy to work with, but you might worry that this type of wood can suffer from wood rot since wood rot is one of the most dangerous types of hazards for a home. Not only is it bad for your home’s aesthetic, but it can also be hazardous to you and your family’s health and safety. Pressure-treated wood is not immune to wood rot since fungal issues can creep into the wood. However, knowing what wood rot is and how you can prevent it from affecting pressure-treated wood can keep your home safe.

What Is Pressure-Treated Wood?

Wet pressure-treated wood deck

Image via Pixabay by PublicDomainPictures

Used for more than half a century, pressure-treated wood is used where there’s direct contact between wood and anything that could supply moisture. It’s usually found on a variety of exterior surfaces such as porches, decks, and fences as well as exterior door and window sills. 

To make pressure-treated wood, the lumber goes into a pressure chamber that has a horizontal steel cylinder that’s called a retort. This piece of machinery resembles a rail car. After the wood is secured properly within the retort, a vacuum removes all the air from the cylinder as well as the wood’s cell structure.

The retort uses 160 pounds of pressure to drive preservative agents into the cell structure of the wood. These agents, which are meant to preserve the wood’s lifespan, typically include copper azole (CA), copper quaternary (ACQ), and micronized copper azole (MCA). When placed inside the wood, the agents react with the fibers and slow the natural decay. They also contain properties that resist termites, moisture, and fungus. 

Once the pressure treatment is finished, the wood is relocated to a drip pad to cure and dry enough for shipment. Before you use the wood for your project, you need to make sure the wood is completely dry. To do this, sprinkle some water on the wood. If the droplets are absorbed into the wood, it’s ready to be painted or stained. However, if the water beads on the surface, the wood needs a few more days to dry completely.

How Does Wood Rot Happen?

Even though pressure-treated wood contains properties that can resist moisture and fungus, it doesn’t mean this type of wood is entirely resistant to damage. One of the most common reasons for wood rot in pressure-treated wood is due to fungi. These very small organisms take up residence in the wood and feed on it over time. Their movement causes the wood to decay and soften, eventually causing the wood to rot. Because dry rot is a fungus, it can spread throughout the wood, so it’s best to take care of the problem immediately.

Often wood rot isn’t obvious unless you’re specifically looking for it. Every year, you should inspect your property to take note of any repairs you need to schedule for the upcoming year. Pay particular attention to the following spots:

  • Exterior window railings and sills.
  • Exterior wood stairs, particularly in areas near the base.
  • The area where wood siding meets the trim.
  • The area where two pieces of trim join together.
  • Deck beams or supports.

When you look at the wood and notice a spot might be rotting out, press your fingers to the wood. If the wood feels soft or crumbles easily when you touch it, you might have wood rot. Other signs you can look for to determine if you have wood rot include the following:

  • Black spots.
  • Soft spots in the wood.
  • Black fungi.
  • Odd or musty smells.
  • Cracked or crumbling wood.

How Do You Stop Wood Rot?

To completely prevent wood rot from spreading, you need to kill the fungus. In certain cases, you might be able to find the leak or drainage issue causing the excess moisture to settle on the wood. Other times, you might need to do a little research to find the source of the water. Once you find the cause of the water, try to relocate the drain or add a way for the water to disburse elsewhere.

To treat the wood rot, your next step involves killing off the fungus that’s ruining the pressure-treated wood. Boric acid, or borate, is one of the most effective types of fungicides on the market to treat wood rot. Apply it to the wood to stop an active decaying fungus from growing. If the affected area is relatively small and in a non-supported area, you can usually remove the damaged wood and rebuild it with wood filler. However, if the damaged area is larger or in a load-bearing area, you must replace the pressure-treated wood.

How Do You Prevent Wood Rot?

The best way to prevent wood rot is to keep the wood dry. Obviously, if your pressure-treated wood is part of your deck, that might be difficult to accomplish, especially if it’s outside and subject to inclement weather. Pressure-treated wood can crack and eventually split from too much water exposure, which allows fungi to seep into the cracks and form wood rot.

Consider applying a deck preservative, which can include varnishes, oils, paint, waxes, or any other type of substance that can enhance the wood’s longevity. You might also want to apply protectors that contain a fire retardant to keep you and your family safe. To prevent future rot, you can also apply boric acid during construction. Keep in mind that you will need to apply these preservatives periodically, at least once a year. These products aren’t meant to keep out moisture for the life of your wood, but a higher-grade sealant will give you longer protection.

Moisture is a breeding ground for fungus, so it’s best to practice preventative measures when it comes to your pressure-treated wood. Regularly cleaning and inspecting the wood’s exposure to moisture can also remedy any source of moisture that might develop before it has a chance to do serious harm. If you need further assistance in treating any pressure-treated wood at your home, reach out to Teak Masters. We offer a variety of restoration services to protect the wood’s surface from moisture. 

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