Despite its durability, pressure-treated wood can still succumb to harsh elements over time, leaving you with unsightly and unsafe structures. To avoid experiencing these, understanding how long pressure-treated wood lasts is beneficial.
To give you an informed decision about this type of wood for your outdoor project, our woodworkers will guide you to learn more about pressure-treated wood and its lifespan.
What to Know About Pressure-Treated Wood: How it’s Treated
The treatment process begins with placing the wood in a large depressurized holding tank, where it is infused with a chemical solution under high pressure to remove wood excess air.
The chemical solution in pressure treatments typically includes copper, which is a natural fungicide, as well as other chemical treatment that resist rot and insect damage.
Types and Lumber Grades of Pressure-Treated Wood
Lumber classified as #1 grade is of higher quality and has a better appearance, with fewer defects such as warping, blemishes, and knots. It is commonly used for visible decking and railing projects due to its premium quality.
On the other hand, #2, or construction grade lumber, has a rougher appearance and is usually used for framing and other non-aesthetic projects.
Benefits, Uses of Pressure-Treated Wood
The benefits of pressure-treated wood are:
- Durability: Pressure-treated lumber is treated with chemicals that make it resistant to rot, decay, and insect damage, making it a long-lasting option for outdoor structures.
- Cost-effective: Compared to other wood species, pressure-treated lumber is relatively inexpensive, making it a popular choice for budget-conscious projects.
- Versatile: Pressure-treated lumber is available in various sizes, types, and grades, making it suitable for various projects.
- Low maintenance: It requires minimal maintenance compared to other wood species, making it a convenient option for outdoor application.
Pressure-treated wood is commonly used in the following:
- Decks: Treated lumber is a popular choice for deck construction due to its durability, cost-effectiveness, and ease of installation.
- Fences: It is a common choice for fencing due to its resistance to rot, decay, and insect damage, making it ideal for long-lasting outdoor structures.
- Retaining walls: Treated lumber is often used in retaining wall construction due to its ability to resist water damage and prevent soil erosion.
- Playsets: It is a safe and durable option for playset construction, as it can withstand heavy use and exposure to the elements.
The Lifespan of Pressure-Treated Lumber + Indicating Factors
On average, pressure-treated wood last anywhere from 20 to 50 years, depending on the level of exposure to the elements and the quality of its installation.
In some cases, pressure-treated lumber can last even longer if it is well-maintained and protected from excessive moisture and sunlight. However, the lifespan of treated lumber highly depends on the following factors:
Maintenance
By taking adequate care and maintenance, the pressure-treated wood’s longevity can be extended. Proper upkeep and attention can prevent damage that may be caused by extreme temperature changes, sun, and rain.
To protect decks and other outdoor structures, we recommend applying a water repellent about six weeks after construction and annually.
Type of Wood
Different types of wood have varying abilities to absorb and retain the chemicals used in pressure treatment. This leads to varying levels of durability when used in different applications.
Certain wood species are better suited for pressure treatment and are more long-lasting than others. The top-performing wood species for this purpose are:
- Hem-Fir is a type of western species that is less sturdy than Douglas fir, more susceptible to warping and splitting, but very responsive to preservation methods.
- Douglas Fir is mainly utilized in the western regions of the United States and Canada.
- Southern Pine is frequently used for deck framing due to its strong logs and high sapwood content that efficiently absorbs preservatives.
Climate/Temperature
In regions with high humidity or sub-tropical climates, a pressure-treated deck is more susceptible to decay because they absorb moisture and come into contact with damp plants, shrubs, and trees.
Usage
Vertical wood construction usually has a more extended lifespan than horizontal wood projects, as the former can expel moisture more efficiently.
Chemical Preservatives
The pressure treatment process is created by injecting preservative chemicals into the wood in a vacuum-sealed, pressurized tank [1].
The type and amount of chemical preservative used and its depth of penetration determine how long the wood will last. But if you want to discard it, can you burn pressure-treated wood? Find answers here.
Type of Project
The type of project determines the amount and type of wood pressure treatment needed for the wood, which affects its lifespan.
The amount of preservative required is called “chemical retention levels” and varies depending on the use and stress placed on the wood.
The Lifespan of Pressure-Treated vs Untreated Deck
On average, a pressure-treated wood deck can last up to 25 years with proper maintenance, while untreated decks may only last 10 to 15 years.
However, it’s important to note that the lifespan of a deck is influenced by factors such as climate, exposure to the elements, and maintenance practices.
What Causes Pressure-Treated Lumber to Rot?
Lack of Air Circulation
Even properly maintained pressure-treated wood rot due to a lack of airflow and moisture buildup, especially in areas close to the ground, surrounded by vegetation, or near water.
Using UC4 B-treated wood and improving airflow can help prevent rot and retain moisture.
Fungal Infestations
Fungi can cause rot in treated wood, despite initial protection from fungicides in the treatment process.
Fungi can penetrate the wood and weaken it from within, leading to decay and rot. Regular treatment with fungicides can help protect pressure-treated structures.
Dirt and Vegetation
Leaving dirt and dead vegetation on a deck or structural members can trap moisture and seeds, leading to moisture damage and rot. These seeds can even penetrate the wood and cause rot.
To prevent this, it’s important to sweep or wash off dirt and dead vegetation from the structure regularly.
Moisture
Pressure-treated wood rot because of weathering, particularly deck boards, as they expand and contract with seasonal changes.
This can result in cupping or splitting of the boards, which can allow moisture to penetrate deeper into the wood, causing rot.
Applying Paint, Stain, or Sealant Before it Dries
Should You Paint or Stain It?
It is possible to paint or stain pressure-treated wood. In fact, it’s recommended to do so to maintain its quality and durability over time.
Annual maintenance, such as staining and washing with a high-intensity washer, will help to repel moisture and keep the wood in good condition.
Do You Need to Seal It?
Sealing pressure-treated wood is not always necessary, but it can provide an extra layer of protection against prolonged moisture and UV rays, helping to extend the lifespan of the wood.
Sealing is particularly important if the wood will be exposed to the elements or if it will be used in a high-traffic area.
Protecting Pressure Treated Wood + How to Extend its Lifespan
Drying
After the process of pressure treating wood, it takes some time for the wood to dry before painting, staining, or sealing it. It’s necessary to wait for weeks or months before applying these treatments.
To check if the wood is completely dry, sprinkle some water on it, and if it absorbs the droplets, it’s ready to be treated.
Sealing
Applying sealers that resist or repel water annually and using mildewcide cleaner at first sight of mildew is essential for maintaining the quality of pressure-treated wood. These steps help prolong the lifespan of the wood.
Maintaining
Regular maintenance is required for pressure-treated wood to prevent mildew and rot. Clear snow and leaves regularly, and cut back or prune any plants or foliage near the wood to help it dry more easily.
Best Pressure-Treated Wood for Ground Contact
UC4A Uses
- Ideal for building docks, decking, stringers, and boardwalks
- Suitable for use in ledger boards, joists, beams, and posts that are hard to maintain, repair, or replace
- Limited airflow
- Extended contact with damp vegetation or leaves
- Damp environments, frequent moisture exposure, and tropical climates
- Light ground contact wood
- Suitable for use within 6 inches of above-ground contact level
- Standard decay exposure
UC4B Uses
- Suitable for use in a tropical climate or all weather cycles
- Recommended for marine structures that come into direct contact with freshwater or saltwater spray
- Suitable for garden beds, wood posts, utility poles, or cross-ties that require long-term durability
- Ideal for ground contact use or wood foundations that have high exposure to decay potential
- Suitable for heavy-duty ground contact or framing members that are difficult to maintain or replace
- Recommended for posts that support permanent structures, docks, or piers
UC4C Uses
- It is commonly used for freshwater, land, and building pilings, as well as utility poles and cross-ties in areas with a high risk of decay.
- UC4C is used in cases with a high risk of exposure to decay and extreme weather cycles.
- This treatment is also suitable for structural components in contact with soil or freshwater.
- UC4C is recommended for applications that involve direct ground contact lumber with soil or installation in concrete or gravel.
Is Pressure-Treated Wood Safe?
Pressure-treated lumber is wood treated with chemicals, including copper-based preservatives like CCA or chromated copper arsenate, that were once considered harmful.
However, newer chemicals with less toxic chemicals have been developed for pressure treatment processes like alkaline copper quaternary, and many of the wood industry choose not to use CCA-treated wood.
Moreover, to avoid risks, it’s important to wear protective gear when handling pressure-treated wood and avoid burning it.
Bonus Tips When Working with Treated Wood
- Use HDG or stainless steel nails, fasteners, bolts, and screws to avoid corrosion caused by the copper coating.
- Do not burn pressure-treated wood
- Work with pressure-treated wood outdoors
- Keep children, pets, water, and food away from the wood
- Wear protective gear (gloves, goggles, masks)
Is there a Warranty Period for Pressure-Treated Lumber?
Yes, pressure-treated lumber usually comes with a warranty period, but the specifics can vary depending on the manufacturer and the product. In general, the warranty period for treated lumber can range from 20 to 50 years or more.
Conclusion
Knowing how long does pressure-treated wood last is beneficial if you are considering using this type of wood for outdoor projects.
While its lifespan can vary based on several factors, it generally offers a longer lifespan than untreated wood. However, it still requires proper care and maintenance to ensure longevity.
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