How long does a deck last? Most contractors will not answer that question on their website. They worry the answer will scare you off or start a conversation they do not want to have. We are going to answer it anyway, with real numbers, real trade-offs, and the information you need to make a smart investment decision.
The Honest Answer: It Depends on What It Is Made Of
Most homeowners researching deck lifespan are really asking a comparative question: How long does a wood deck last compared to a composite deck? The gap between those two answers is significant, and understanding it is the first step toward choosing a material you will not regret.
Deck Lifespan by Material
| Material | Product Examples | Average Lifespan | Maintenance Required |
| Pressure-treated pine | Standard PT lumber | 12 to 18 years | High (seal every 1 to 3 years) |
| Composite, entry-level | Trex Select, Trex Enhance | 25 to 30 years | Low (annual cleaning) |
| Composite, premium | Trex Transcend, TimberTech PRO | 30 to 40 years | Very low (occasional cleaning) |
| Full PVC | TimberTech AZEK | 40 to 50+ years | Minimal |
Ranges based on a 400 sq ft deck in the Des Moines metro area. Site conditions, design complexity, and substructure specs affect the final number.
Wood vs. Composite: The Comparison Every Homeowner Is Already Making
It is one of the most common comparisons homeowners research, and the honest answer is that wood and composite are not competing on equal ground.
Wood decking:
- Lower upfront cost, but requires sealing every 1 to 3 years
- Susceptible to UV damage, rot, and Iowa’s freeze-thaw cycle
- Structural wear is common by year 15
Composite decking:
- Higher upfront cost, minimal maintenance after installation
- Resists rot, insects, UV fading, and moisture
- Surface warranty runs 25 to 30 years from installation
- A composite deck at year 15 typically looks close to how it did at year one
The gap in long-term performance is significant. For a homeowner making a serious investment in their outdoor space, composite decking is not just the more durable option. It is the one that actually holds its value. See a full material comparison before making a call.
Why Wood Falls Short
Pine boards are pressure-saturated with alkaline copper quaternary compounds that fight rot and insects. What those compounds do not fight is UV radiation or Iowa’s freeze-thaw cycle. Skip a sealing cycle or two, and the damage compounds quickly:
- Surface fibers begin breaking down
- Moisture penetrates deeper into the grain each season
- Structural integrity erodes from the inside out
- By the time cracking and graying appear on the surface, the damage underneath is already irreversible
Pro Tip: New pressure-treated lumber arrives at the job site wet. Let it dry for at least 30 days before sealing. Applying a sealer to wet wood traps moisture, causing the sealer to fail within months. Most homeowners who report early sealer failure skipped this step.
The lower upfront price of a wood deck comes with real ongoing costs: time, attention, and eventual replacement. That math matters more than the sticker price.
Composite Decking: What the Warranty Actually Covers
Composite decking is where most Des Moines homeowners land when they weigh long-term value against upfront cost. Products like Trex and TimberTech combine wood fiber and recycled plastic polymers into boards that resist rot, insects, UV fading, and moisture at a level wood simply cannot match.
Expected composite deck lifespan: 25 to 50 years, depending on product tier.
The biggest source of confusion is the warranty. Trex products carry a 25-year warranty covering fade, stain, and structural performance. TimberTech products step up to 30 years across the same categories. What neither brand covers is the substructure beneath the boards: The joists, beams, and fasteners that hold everything together.
That framing system is where installation quality determines how long the deck actually performs, regardless of what the surface warranty says.
Pro Tip: Before signing anything, ask your contractor specifically what covers the framing system. A warranty on the boards alone is partial protection. See the full warranty details here.
Three Things That Kill a Deck Before Its Time
Material choice matters. Installation quality matters more. Premature deck failure almost never traces back to the material itself. It traces back to one of these three problems:
1. Ledger Board Failure
The ledger board connects your deck to the house. When it is improperly flashed, moisture finds the connection point and works into the house’s rim joist. This is the most common cause of structural deck failure and the most expensive to repair. Proper ledger installation requires a waterproofing membrane, metal flashing, and lag bolts or structural screws driven into house framing. Never nails.
2. Footings That Do Not Reach Frost Depth
Iowa frost depth in the Des Moines metro runs 42 to 48 inches. Footings poured above the frost line heave every winter, racking the frame out of level and loosening post-to-beam connections. A deck that creaks and shifts after two winters almost certainly has a footing depth problem, not a material problem.
3. Blocked Drainage Beneath the Deck
Wood substructures rot from the bottom up when air cannot circulate beneath the deck. Composite boards can develop mold on their underside for the same reason. Proper joist spacing, adequate ground clearance, and clearing debris between boards significantly extend structural life, regardless of what the surface boards are made of.
The Cost Question Nobody Asks Until It Is Too Late
Homeowners focused on the upfront price often skip the math that matters more: Cost per year of use.
20-Year Cost of Ownership (400 Sq Ft Deck, Des Moines Metro)
| Material | Install Cost | Est. Maintenance (20 yrs) | Replacement Before Year 20? | Total 20-Year Cost |
| Pressure-treated pine | $ | $$$ | Yes, likely | $$$$ |
| Entry-level composite (Trex Select / Enhance) | $$ | $ | No | $$ |
| Premium composite (Trex Transcend / TimberTech) | $$$ | $ | No | $$$ |
More dollar signs = higher relative cost. Ranges vary based on deck size, site conditions, and material selection.
Here is what most contractors will not tell you: The cheaper deck often costs more in the long run. Three takeaways from the table above:
- Pressure-treated pine carries the lowest sticker price and the highest 20-year cost, once maintenance and likely replacement are factored in.
- Entry-level composite hits the value sweet spot: Meaningfully lower total cost than wood, without the premium price of top-tier boards.
- Premium composite costs more upfront and less over time than any other option on the list.
Upfront cost and total cost are two completely different numbers. Most contractors only talk about the first one.
How to Tell If Your Existing Deck Is Near the End
Before calling anyone, do a quick physical inspection:
- Probe the joists and ledger board with a flathead screwdriver. If the tip sinks in without resistance, the wood is rotting from the inside. Softness at the ledger is the highest-priority warning on this list, as it is the structural connection to your house.
- Push on each post at the base. Movement or soft wood at ground level means the post is compromised.
- Step across every board. Any that flex, spring, or feel soft underfoot need immediate attention.
- Check the fasteners. Corroded screws and popped nail heads signal that wood has swelled and shifted enough to break the mechanical connection.
A deck that fails one or two of those checks may be repairable. Three or more is usually a replacement conversation.
Frequently Asked Questions
How long does it take to build a deck?
Most residential decks take 3 to 7 days of active construction. Covered structures, multi-level designs, and custom features add time. Permitting is handled before the build starts.
Can a deck be built in winter in Des Moines?
Yes. Concrete footings require ground temperatures above freezing to cure, but framing and decking can proceed through most of Iowa’s winter months. Winter builds also tend to have shorter lead times.
Do I need a permit to build a deck in Des Moines?
In most cases, yes. Any deck attached to a house or built above a certain height requires a building permit in Iowa. Skipping it can create issues at resale and may void homeowners’ insurance coverage.
How do I choose between Trex and TimberTech?
Both carry strong warranties and proven track records. Trex offers a wider color range at the entry level. TimberTech AZEK is made entirely of PVC, with no wood fiber, making it the stronger pick for high-moisture areas. The right choice depends on budget, aesthetics, and site conditions.
Get a Straight Answer Before You Commit
Knowing how long a deck lasts starts with understanding what it is made of and how it is put together. The homeowners who make the best decisions are the ones who ask the hard questions before the project starts, not after.
If you are planning a new deck or evaluating an existing one, request a free estimate. You will get honest material comparisons, real numbers, and a design process built around your site, not a catalog page.
