Pressure-treated pine is the default choice for residential decks in many parts of the world. It’s cheap, widely available, and every contractor knows how to work with it. Black Locust costs more upfront. End of conversation for many buyers.
But the upfront cost comparison is only part of the story. Here’s what the full 10-year picture looks like.
The Upfront Cost
Let’s use a realistic residential deck: 400 square feet, standard decking profile.
- Pressure-treated pine (standard grade): roughly $2–4 per linear foot
- Black Locust decking: roughly $5–9 per linear foot depending on grade and length
On a 400 sq ft deck, the material cost difference is typically $800–$2,000 in favor of pressure-treated pine. That’s a real number, and it’s fair to acknowledge it.
Year 1–3: Maintenance Begins
Pressure-treated pine requires sealing within the first year of installation to prevent cracking, checking, and accelerated weathering. A quality deck sealant applied by a professional to a 400 sq ft deck typically runs $200–$400 in materials and labor. This needs to be reapplied every 2–3 years.
Black Locust, left to weather naturally to its silver-gray patina, requires no sealing or treatment. If you prefer to maintain the natural amber color, an oil application costs roughly $100–$200 every 1–2 years.
By year 3: pressure-treated pine has incurred $200–$400 in maintenance. Black Locust: $0–$200.
Year 5–7: The Refinishing Question
Pressure-treated pine typically shows significant weathering, checking, and color degradation by year 5–7. A deck refinishing — strip, sand, reseal — runs $800–$1,500 for a 400 sq ft deck. Many homeowners do this once or twice over a 10-year period.
A well-maintained Black Locust deck at year 5–7 looks essentially the same as it did at year 2. The wood’s natural character develops — the silver-gray patina or the maintained amber tone — but there’s no significant structural weathering, no checking requiring repair, and no stripping required.
Year 10: Where Do You Stand?
Cumulative cost estimate for a 400 sq ft deck over 10 years:
- Pressure-treated pine: $2,000–4,000 materials + $1,500–3,500 maintenance/refinishing = $3,500–7,500 total
- Black Locust: $3,000–6,000 materials + $500–1,500 maintenance = $3,500–7,500 total
The 10-year total cost ranges overlap significantly. And this calculation doesn’t account for the possibility of partial or full deck replacement for treated pine — which is common at or before the 15-year mark due to rot in boards or structural framing. Black Locust at 10 years is still in its youth as decks go.
The Beyond-10-Year Picture
A quality Black Locust deck, properly installed, should last 25–40 years with minimal maintenance. A pressure-treated pine deck in the same timeframe typically requires significant board replacement at 10–15 years and potentially a full rebuild at 15–20 years. The cost of a second deck build eliminates any early price advantage entirely.
The Bottom Line (On Pressure-Treated Pine)
Black Locust costs more upfront. Over a 10-year horizon, the total cost of ownership is roughly comparable to pressure-treated pine. Over 20–30 years, Black Locust is almost certainly the less expensive choice — while also performing better, looking better, and avoiding the chemical treatment questions associated with ACQ and copper azole-treated lumber.
For those who value both financial return and environmental responsibility, Black Locust offers something pressure-treated pine never can: a fast-growing, chemical-free material that doesn’t deplete old-growth forests or leach preservatives into the environment. Compare all decking species →
