1×2 Treated Lumber in Construction in USA

Understanding the Actual Dimensions of 1×2 Treated Lumber

In U.S. construction, the term 1×2 refers to the nominal size of the lumber, but the actual dimensions are 0.75 inches thick by 1.5 inches wide. This dimensional reduction is the result of the lumber being planed and dried after its initial rough cut, a standard process for all dimensional lumber used in building applications.

• Nominal Size: 1 inch x 2 inches
• Actual Size: 0.75 inches x 1.5 inches

Despite its small profile, 1×2 treated lumber serves a multitude of functions in both residential and commercial construction environments across the United States.

Benefits of Pressure-Treated 1×2 Lumber in Construction

Resistance to Moisture, Rot, and Insects

1×2 pressure-treated lumber is infused with chemical preservatives during manufacturing. These preservatives make the wood resistant to rot, mold, fungal decay, and insect infestation, making it ideal for environments exposed to moisture or ground contact.

Extended Lifespan

With proper installation and periodic maintenance, treated 1×2 boards can last 20 years or more in exposed conditions. This durability makes them a cost-effective material for long-term structural and non-structural applications.

Common Applications of 1×2 Treated Lumber

Trim and Furring Strips

One of the most widespread uses of 1×2 treated lumber is for furring strips—thin wooden supports used to:

• Level surfaces for drywall or paneling installation
• Provide backing for exterior siding
• Space out insulation or sheathing materials

Because of its uniform size and durability, it performs well as a trim board, especially around windows, doors, and rooflines in moisture-prone areas.

Garden and Outdoor Structures

In outdoor construction, 1×2 pressure-treated boards are used for:

• Garden trellises
• Greenhouse framing
• Fence lattice construction
• Planter box edging

Their small size is ideal for light-duty framing, aesthetic detailing, and projects where space efficiency is essential.

Underlayment and Lath Work

For plaster wall systems, 1×2 treated laths are installed horizontally across studs. They support the application of wet plaster, preventing cracking and ensuring adherence over time, especially in humid climates.

Availability and Lumber Grades for 1×2 Treated Boards

Standard Lengths and Lumber Yard Options

1×2 treated boards are typically available in the following lengths:

• 8 feet
• 10 feet
• 12 feet
• 16 feet

Longer lengths are available in select specialty lumberyards or for commercial bulk orders.

Grades of Treated Lumber

Treated lumber comes in various appearance and structural grades, including:

• Standard & Better (Std & Btr)
• Select Structural
• Appearance Grade

Most 1×2 boards are intended for non-load-bearing applications and are therefore graded more for appearance and treat penetration than structural strength.

Treatment Types and Preservatives Used in 1×2 Lumber

ACQ and MCA Treatments

The most common preservatives for 1×2 treated lumber include:

• Alkaline Copper Quaternary (ACQ)
• Micronized Copper Azole (MCA)

Both are EPA-registered treatments that offer superior decay and insect resistance, making the lumber safe for residential use, including playgrounds, raised beds, and decks.

Ground Contact vs. Above Ground Use

1×2 treated wood is generally labeled for Above Ground Use. However, if used in environments with high moisture or contact with soil, ensure it’s rated for Ground Contact, which provides deeper preservative penetration.

Fasteners and Installation Practices for 1×2 Treated Wood

Corrosion-Resistant Fasteners

Treated lumber must be paired with hot-dipped galvanized, stainless steel, or coated fasteners to prevent corrosion caused by preservative chemicals.

Common fastener types include:

• Exterior-grade screws (deck screws)
• Ring-shank nails
• Framing anchors and connectors

Spacing and Support Guidelines

Due to its narrow cross-section, 1×2 lumber requires frequent support when used horizontally. Vertical spacings of 12 to 16 inches are typical for secure furring strips or lath support.

When used for trim, proper bracing and anchoring ensure the board does not warp over time due to environmental stress.

Fire Retardant and Environmental Considerations

Fire-Retardant Options

Some 1×2 treated boards are available with fire-retardant treatments, especially for use in:

• Multifamily housing
• Public facilities
• Building egress systems

These boards comply with local fire codes and are rated for interior or exterior fire resistance based on application.

Environmental Impact and Safety

Modern preservatives used in pressure-treated lumber are safer and more eco-conscious than past formulations like Chromated Copper Arsenate (CCA). MCA-treated 1x2s are suitable for:

• Residential gardens
• Play equipment
• Pet enclosures

Proper disposal of off-cuts and unused lumber should always follow local waste regulations to prevent soil or water contamination.

Cost and Market Availability

Retail Pricing

1×2 pressure-treated boards are among the most affordable treated lumber options. Prices vary by region, wood species, and length but typically fall in the range of:

• $1.50 to $3.50 per board (for 8-foot lengths)
• Bulk purchases may reduce per-unit cost

Pricing is affected by lumber market conditions, which fluctuate based on season, transportation, and availability of raw materials.

Wood Species

Common species used for 1×2 treated lumber include:

• Southern Yellow Pine
• Douglas Fir
• Hem-Fir

Each species offers different characteristics in terms of weight, grain, durability, and resin content. Southern Yellow Pine is the most widely treated and commercially available.

Maintenance of Treated 1×2 Lumber in Construction

Sealing and Finishing

Although pressure-treated 1x2s are rot-resistant, applying a sealant or paint can extend their life further, especially in exposed locations. Wait for the lumber to fully dry before applying finishes.

Recommended finishes include:

• Oil-based wood sealers
• Exterior-grade paint or stain
• UV-resistant coatings

Annual Inspection

Routine inspection for signs of:

• Cracking
• Warping
• Surface mold

can ensure early maintenance and prevent long-term deterioration. Re-coating every 2–3 years is recommended for exterior installations.

Conclusion

The 1×2 treated lumber plays an essential role in residential and light commercial construction across the USA. With actual dimensions of 0.75 inches by 1.5 inches, this small but versatile material provides dependable support in furring, trim, garden, and utility applications. Its rot resistance, availability, and affordability make it a smart choice for professionals and DIY builders alike. When used with corrosion-resistant fasteners, finished with proper sealers, and installed following spacing guidelines, 1×2 treated boards will deliver reliable performance for years to come.