Do I need to treat cuts on pressure-treated wood?

Yes. When you cut, drill, or notch pressure-treated lumber, you expose untreated wood that has no preservative protection. Apply an EPA-registered brush-on preservative like copper naphthenate to all field cuts, allowing it to soak in before assembly. This is especially important for cuts near ground contact or moisture exposure.

Are wood preservatives safe for raised garden beds?

Modern ACQ and CA-C pressure-treated lumber is considered safe for garden bed use according to EPA guidelines. For additional peace of mind, line the inside of beds with plastic sheeting to prevent direct soil-to-wood contact. Borate treatments are low-toxicity and break down in soil. Avoid using CCA-treated wood (pre-2004 vintage) for any food-contact application.

How long does wood preservative last?

Factory pressure-treated wood can last 20-40+ years above ground and 15-25 years in ground contact. Brush-on preservatives at field cuts provide 5-15 years of protection depending on exposure. Borate treatments in protected interior applications last the life of the structure. Reapply brush-on treatments if the wood is re-cut or damaged.

Finishes & Coatings

Wood Preservatives Guide: Protect Against Rot, Insects, and Decay (2026)

Prepared by Lumberama's Hardware & Accessories Team

|Last updated July 9, 2026|Sources & methodology

Wood preservatives extend the useful life of lumber by preventing fungal decay, insect damage, and moisture deterioration. Whether you are treating field cuts on pressure-treated lumber, preserving untreated wood for ground contact, or protecting timbers from termites, the right preservative can add decades of service life. This guide covers available treatment options from brush-on borate solutions to professional-grade copper compounds.

Key Takeaways

Wood preservatives extend the useful life of lumber by preventing fungal decay, insect damage, and moisture deterioration.
Whether you are treating field cuts on pressure-treated lumber, preserving untreated wood for ground contact, or protecting timbers from termites, the right preservative can add decades of service life.
This guide covers available treatment options from brush-on borate solutions to professional-grade copper compounds.
End use (ground contact vs above ground vs interior), target threats (fungal rot, termites, carpenter ants, marine borers), application method (brush-on, spray, dip, or pressure treatment), environmental and health considerations, compatibility with finishes and coatings, EPA registration status, and whether you need to treat field cuts on factory-treated lumber.
Copper Green wood preservative provides brush-on copper naphthenate protection for ground-contact and below-grade wood.

What to Consider

End use (ground contact vs above ground vs interior), target threats (fungal rot, termites, carpenter ants, marine borers), application method (brush-on, spray, dip, or pressure treatment), environmental and health considerations, compatibility with finishes and coatings, EPA registration status, and whether you need to treat field cuts on factory-treated lumber.

Product Comparison

Copper Green wood preservative provides brush-on copper naphthenate protection for ground-contact and below-grade wood. Bora-Care is a borate-based treatment that penetrates deep into bare wood to prevent termites, carpenter ants, and fungal decay with low toxicity. Tim-bor is a powdered borate that mixes with water for spray application on framing and structural lumber. Penofin Verde is a plant-based preservative oil with lower environmental impact.

Size Selection Guide

Brush-on preservatives cover 100-200 sq ft per quart on smooth surfaces. Borate solutions cover 200-250 sq ft per gallon when sprayed on bare wood. For field-cut treatment on pressure-treated lumber, a quart of end-cut preservative is sufficient for most deck projects. Whole-log treatment with borate requires significantly more product — calculate based on total surface area and absorption rate.

Installation Tips

Apply brush-on preservatives liberally to all field cuts, holes, and notches in pressure-treated lumber before assembly. Borate treatments work best on bare, unsealed wood — the wood must be able to absorb the solution. Apply multiple coats until the wood stops absorbing. Allow full drying before painting, staining, or covering. Treat end grain and cut surfaces especially thoroughly as these are the primary moisture entry points.

Common Mistakes to Avoid

Forgetting to treat field cuts on pressure-treated wood, leaving exposed untreated wood that rots first. Applying borate treatments to sealed or painted wood where they cannot penetrate. Using preservatives that are not rated for ground contact in below-grade applications. Not allowing adequate drying time before covering treated wood. Assuming that pressure-treated wood never needs additional preservative treatment.

Budget Guide

End-cut preservative costs $8-15 per quart. Copper naphthenate brush-on runs $15-25 per gallon. Borate treatments cost $40-80 per gallon of concentrate (makes 5-10 gallons of solution). Tim-bor powder costs $20-30 per 1.5-lb bag treating up to 1,000 sq ft. For a standard deck build, $15-30 in end-cut preservative covers all field cuts.