Pressure's On: How Treated Lumber Stands Strong
Treated lumber is important in the United States because it is resistant to fungal decay, insect damage, and weathering. The process of pressure-treating uses high pressure to drive preservative chemicals deep into the wood.
When lumber is pressure-treated, it increases the wood's lifespan. This readies it for outdoor applications like decks, fences, and landscaping projects. This is essential since the lumber will be in contact with the ground.
Pressure Treated Lumber
Pressure-treated lumber prices are higher than regular untreated lumber because of higher manufacturing costs. Prices can also vary based on lumber size, wood species, preservative type, and treating plant location.
In the US, common sizes include 2x4, 2x6 and 4x4 posts, though one can reasonably treat any size.
- 2x4 pressure-treated lumber for deck framing, fencing, etc.
- 2x6 pressure-treated lumber for joists, retaining walls, etc.
- 4x4 pressure-treated posts for deck supports, fence posts, etc.
Applications of treated 2x4s
2 x 4 pressure-treated lumber is commonly used for framing in construction projects such as:
- Framing walls, floors, and roofs in house and building construction
- Building sheds, barns, and other outdoor structures
- Framing decks and fences
- General carpentry and DIY projects requiring dimensional lumber
The 2x4 size (actually measuring 1.5" x 3.5") provides strength and rigidity while still being relatively lightweight and easy to use. Its narrow width makes it ideal for framing.
Applications of treated 2x6s
2x6 pressure-treated lumber has several common applications, including:
- Deck framing and joists for added strength and span
- Stair stringers for outdoor steps and staircases
- Handrails and guardrails for decks and porches
- Fence rails and top caps for long-lasting fencing
- Landscaping projects like retaining walls and raised garden beds
The larger pressure-treated 2x6 dimension (actually 1.5" x 5.5") provides increased load-bearing capacity compared to 2x4s. It's good when extra length is needed between supports. A few good tips concerning pressure-treated deck lumber are to seal or treat any cut ends. This will keep the integrity of the treated wood intact and get you the longevity you desire from it.
Applications of treated 4x4s
4x4 pressure treated lumber has several common applications, including:
- Deck posts and support columns for elevated decks
- Fence posts for fencing projects
- Landscape timbers for retaining walls and raised garden beds
- Posts for outdoor structures
The 4x4 dimension (actually 3.5" x 3.5") provides robust structural strength for load-bearing. You would use a 4x4x10 pressure-treated post for a gazebo, for instance. Building codes often mandate its use in structural support where there is contact with soil or concrete. Pressure-treated 4x4 lumber is readily available wherever wood or landscaping products are sold.
Up To Code
Most US building codes require pressure-treated wood where lumber will be exposed to moisture, soil, or concrete. This includes deck framing, fence posts, landscaping timbers, and other ground contact uses.
Proper specification and use of treated lumber help ensure structural integrity and longevity. Building codes provide guidance on approved preservatives, treatment levels, and applications. The thrust is preventing premature decay or failure.
Environmental Concerns
Pressure-treating is an effective wood preservation method, but there are environmental concerns around certain preservatives. CCA (chromated copper arsenate) was popular for a long time but has been phased out in residential settings.
Many treating plants in US have transitioned to alternative preservatives that are less toxic.
Alkaline Copper Quaternary (ACQ) can replace CCA for residential uses like decks and fencing. Copper Azole is another residential preservative containing copper and organic azole fungicides. Micronized Copper Quaternary (MCQ) is a newer residential preservative using finely ground copper particles and an ammonium compound.
Creosote is still widely used in industrial applications like railroad ties and utility poles because of its effectiveness against bugs and weather.
In summary
If you plan to build anything outside that will touch the ground or face the elements, pressure treated lumber is the way to go. It adds some extra cost upfront, but that investment pays off long-term in peace of mind. Much less worrying about rot, insects, or weathering damaging your project. The extra durability means you can spend more time enjoying the outdoors instead of frequently replacing grungy untreated boards.