
Framing a Deck:
Pressure-Treated Lumber vs. Cold-Form Steel
When building a deck, the framing material you choose plays a crucial role in the longevity, maintenance requirements, and overall cost of the project. Traditionally, pressure-treated (PT) wood has been the go-to material for deck framing, but in recent years, cold-formed steel (CFS) has emerged as a viable alternative. While the upfront costs of CFS and PT lumber are now relatively similar, their long-term value is vastly different due to the inherent durability and maintenance requirements of each material.
Pressure Treated Lumber
Pressure-treated lumber is wood that has been chemically treated to resist rot, decay, and insect damage. This process involves forcing preservatives into the wood under high pressure, making it suitable for outdoor applications like decking and framing. Current life expectancy for this lumber is 10-15 years.
Pros

Low Upfront Material Cost
PT lumber is typically cheaper than cold-formed steel in terms of initial material cost.

Ease of Use
It's relatively easy to work with—cutting, nailing, and fastening are straightforward for most contractors and DIY builders.

Traditional Choice
Wood has been used for centuries in construction, so it is a familiar and trusted material.
Cons

Maintenance
Even with treatment, pressure-treated wood can still degrade over time, requiring periodic staining, sealing, and replacement of rotted or damaged pieces.

Vulnerability to Elements
Exposure to moisture, pests, and weather conditions can lead to warping, cracking, and rot.

Shorter Lifespan
While PT wood lasts longer than untreated wood, it doesn’t compare to the longevity of cold-formed steel, especially in humid or coastal climates.
Many deck builders are implementing waterproofing in their frames to improve longevity. Consequently, the labor material costs tied to these methods mean that pressure-treated framing often matches the price of steel framing.
Cold-formed steel refers to steel that is shaped or "formed" at room temperature using machines to create structural components like joists, beams, and studs. These steel components are often galvanized or coated to resist rust and corrosion, making them ideal for framing in demanding environments.
Pros

Durability
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Steel does not rot, warp, or decay. It is also impervious to insect damage and is resistant to rust when properly coated.

Long-Term Investment
CFS has a significantly longer lifespan compared to PT wood—often lasting 50+ years or more with minimal maintenance.

Environmentally Friendly
Steel is 100% recyclable and can be reused, making it a more sustainable choice compared to wood.

Consistent Quality
Steel framing doesn’t suffer from the natural imperfections of wood, such as knots or splits, which can weaken the material.
Cons

Higher Material Cost
While prices for CFS have come down in recent years, it still tends to be more expensive upfront than pressure-treated wood piece for piece.

Specialized Tools & Expertise
Working with steel requires specialized tools and knowledge. Cutting and fastening methods differ from wood, which might increase labor costs or require hiring a specialist.

Potential for Corrosion
If the steel is not properly coated or installed in a way that protects it from moisture, it can rust over time, though proper galvanization prevents this issue.
Many deck builders are implementing waterproofing in their frames to improve longevity. Consequently, the labor material costs tied to these methods mean that pressure-treated framing often matches the price of steel framing.
Cost Comparison: Why Prices Are Becoming Similar
Historically, pressure-treated lumber has been the more affordable choice, largely due to its widespread availability and lower production costs. However, recent advancements in cold-formed steel manufacturing, combined with the increase in demand for more durable and sustainable materials, have narrowed the price gap.
Factors contributing to the price similarity include:
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Improved Manufacturing Processes: As demand for cold-formed steel grows, the industry has scaled up production, reducing material costs.
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Lumber Shortages: Global timber shortages and fluctuations in supply chains have driven up the cost of pressure-treated lumber in recent years.
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Cost of Labor: While steel requires specialized labor, the price of skilled workers in steel framing has become more accessible, further closing the price gap.
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Price vs. Value: The Long-Term Difference
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While the upfront cost of cold-formed steel and pressure-treated wood may now be similar, the long-term value each provides is not. Here's why:
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Pressure-Treated Lumber (Shorter Lifespan):
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Maintenance: Over time, PT wood will need to be repaired or replaced due to rot, warping, and insect damage. These repair costs can add up, especially in harsh climates.
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Lifespan: PT lumber typically lasts around 15-30 years depending on the climate and maintenance practices.
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Cold-Formed Steel (Longer Lifespan):
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Minimal Maintenance: Steel framing does not require regular maintenance or replacement, meaning you won’t have to spend time or money on repairs over the years.
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Lifespan: Steel can last 50+ years without significant degradation, especially if it’s galvanized or coated to prevent rust.
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The True Cost: Understanding Total Ownership
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When comparing materials, it's important to consider Total Cost of Ownership (TCO). While PT wood might appear cheaper initially, over time, the ongoing maintenance and potential repairs can make it more expensive in the long run. On the other hand, cold-formed steel, with its low maintenance and longer lifespan, may present a better value even if the initial cost is higher.
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Conclusion: Choose for Longevity, Not Just Cost
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While both materials have their place in deck framing, the decision ultimately comes down to how long you want your deck to last and how much maintenance you’re willing to commit to. If you're looking for a low-maintenance, long-lasting option that will require fewer repairs and maintenance costs over time, cold-formed steel is an excellent choice. However, if upfront cost is your primary concern and you're okay with the maintenance demands, pressure-treated wood remains a viable option.