Why Steel Deck Frames?
Crippen Woodworks specializing in no-wood deck builds? What?
The irony of a company named Crippen Woodworks pushing steel and other alternative deck frames is not lost on me. I am still a wood guy-a carpenter first-but wood is no longer the durable exterior solution it once was. In order to build things that stand the test of time, we had to adjust to that reality.
Composite decking and railing have been an industry standards for decades now.
Unfortunately, the composite decking is performing far better than the pressure-treated framing supporting it.
We are seeing significant rot in pressure-treated framing in as little as 7 to 10 years. It is reasonable to expect to repair a deck frame and replace some joists or stair stringers within 10 to 15 years of your new build.
The pressure-treated lumber is covered by the manufacturer's warranty but the labor, the more expensive part, is not.
Best Practices for Wood Frames
Joist tape, a self-sealing flashing applied to the top of the joist, is the most common preventative measure against joist decay. This is a great deterrent and one we use on every wood-frame build. It is true that much decay starts at the penetrations made by the decking fasteners on top of the joist, and a high-quality joist tape solves this problem. However, there are multiple sources of decay on and under decks.
The Problem: Fungal and Insect Pressure
The AWPA Wood Decay Hazard Map divides the United States into five distinct Deterioration Zones based on the severity of fungal and insect pressure:
(https://evertrak.com/railroad-tie-rot-zones/ based on AWPA standards)
Zone 1 (Low): Arid and cold climates (e.g., the Intermountain West).
Zone 2 (Moderate): Mild climates with low relative humidity.
Zone 3 (Intermediate): Transverse zones with seasonal moisture changes.
Zone 4 (High): Hot, humid regions—this includes most of Georgia.
Zone 5 (Severe): Warm, humid, high-rainfall regions.
Our decks are under extreme pressure from decay and fungus. While the old CCA pressure-treated lumber was extremely effective against rot, modern copper-based chemical treatments-used in today’s pressure-treated lumber-fail. Unfortunately, two of the most common fungi to attack exterior wood are also extremely copper-tolerant.
Decks that are close to the ground or close to water are extremely susceptible to rot. This also applies to decks with any type of underdeck system. That being said, the deck in the photo below (left) is 6 feet off the ground, well-ventilated and was destroyed by brown rot.
Fungus can enter the wood in the forest or at the mill and be deep enough to not be affected by the pressure treatment process. It can lay dormant until conditions and moisture content are right and then begin to destroy the framing from the inside out.
Brown-Rot Fungi:
(The Most Destructive)
Common regional species include Gloeophyllum trabeum, Rhodonia placenta (formerly Postia placenta), and Serpula lacrymans. These species target the cellulose and hemicellulose in the wood, causing it to shrink, turn brown, and break into small, fragile cubical pieces (often called "dry rot").
White-Rot Fungi:
Common local species include Trametes versicolor (Turkey Tail) and Ganoderma applanatum (Artist's Conk). These fungi break down the lignin—the dark substance that glues wood fibers together—leaving behind a stringy, soft, bleached white rot.
When the residential construction industry phased out arsenic-heavy CCA wood treatments in the early 2000s, it shifted heavily toward copper-based alternatives. However, species like Rhodonia placenta and various fungi in the Antrodia genus have adapted to survive on copper-heavy treated wood.
So, Why Build with Wood at All?
Frankly, if the budget supports eliminating all wood from the exterior of your home in any capacity-including the deck-it’s what I would recommend.
However, wood deck frames are still performing reasonably well, and most will not have any rot issues for 10 to 15 years. It is also important to accept that some warping and bowing of a modern wood deck frame is expected. This is not a structural issue, but if you have an eye for this sort of thing, you will see it. There is no formal study on the longevity of deck frames in Georgia and the Southeast. Based on our own customer base and the experiences of other deck builders I speak with, I believe the failure rate of wood is around 15% - 20%. This is anecdotal and simply my opinion.
As a deck builder who wants to build things that last, I find the failure rate of wood is high enough that I would prefer to never use it again. However, as a service provider attempting to provide the right material to my clients, pressure-treated (PT) wood framing is still often the best fit:
Short-term ownership: Some of our clients have no intention of owning their home for more than 5 to10 years. It is very likely a wood frame will be fine for this timeframe.
Budget constraints: Others may simply not have the budget for a steel frame. A new wood deck is certainly better than an old, unsafe deck.
Risk tolerance: Others may simply be willing to assume the risk. There are far more wood-framed decks that are 20 years old and doing fine than decks that are 10 years old and falling apart.
It is our goal to inform potential clients of all of the options-and the pros and cons of each-so that you can make an informed decision.
"What’s the right material?" isn't the right question. The question we are trying to answer when we work with a customer is: "What is the material that meets this particular client's budget and objectives?"
When Steel or Aluminum is the Best Choice:
Anytime the budget is available. For all of our clients, cost is a factor, but for some, it is not the primary driver. If the finances are available and you want a deck to last a lifetime, eliminate the wood from the build. Metal framing is the best choice if:
The deck is at ground level or you desire an under-deck system.
You want the deck frame to last as long as-or longer than-the material on top of it.
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