Why the estimates vary so much
Ask around and you'll hear very different numbers. A maker of composite decking puts traditional wood at 10 to 15 years. Other published estimates give a well-kept pressure-treated deck 15 to 30. Neither is wrong. They're describing different decks.
A deck that's washed, stained every few years and built with the right lumber in the right places sits at the top of the range. One that's never sealed, stays damp under trees and has ordinary lumber touching the ground sits at the bottom.
The parts wear out at different speeds
The boards
The decking takes the sun, the rain and the foot traffic, so it usually looks old first. Boards gray, check, cup and splinter. That's mostly surface damage, and it's the cheapest part to fix.
The frame
Joists and beams sit out of the sun, but water runs down between the boards and onto their top edges, where it can sit. Rot that starts there is hidden until the boards come up, which is why a deck can look fine and still be soft underneath.
The posts and anything near the ground
Wood that touches soil, or sits close to it, stays wet the longest. This is where the type of treated lumber matters most.
Not all pressure-treated wood is the same
Treated lumber is rated by how much exposure it's meant for. The tag stapled to the end of each board says which:
- UC3B, above ground: for deck boards, railings and framing that stays well clear of the soil and dries out between rains.
- UC4A, ground contact: for posts, and for framing that's close to the ground or hard to keep dry.
- UC4B, heavy duty ground contact: for structural posts buried in soil and other critical uses.
Using above-ground lumber where ground contact lumber belongs is one of the most common reasons a deck fails early. When you buy, read the tag, not just the label on the rack.
What makes a deck last longer
Keep the finish up. Stain or sealer keeps water out of the boards. Finishes don't last long on a deck, though: in a US Forest Service test of 32 deck finishes, the researchers called a 2 to 3 year life excellent. Our guide on how often to stain a deck covers the timing.
Let it dry. Clear leaves out of the gaps between boards, trim plants back from the edges, and keep sprinklers off the deck. Air moving underneath matters as much as the finish on top.
Protect the frame. Many builders put flashing tape on the top of joists and beams before the boards go down, so water can't sit on the wood there. It costs little and can only be done while the deck is open.
Use the right fasteners. Treated lumber is hard on ordinary steel. Screws, nails and connectors should be rated for treated wood, usually hot-dip galvanized or stainless.
Signs a deck is wearing out
- Boards that flex or feel spongy underfoot.
- A screwdriver that sinks into a joist, beam or post instead of stopping at the surface.
- Rust streaks, or fasteners that are loose or pulling out.
- A gap opening between the deck and the house, or a ledger board that looks stained or wet.
- A railing that moves when you lean on it.
- Posts that are cracked, soft or leaning at the base.
Any of the last three is a reason to stop using the deck until someone has looked at it. Those are the parts that hold people up.
Resurface or rebuild?
If the boards are tired but the frame and posts are sound, new boards on the old frame cost a fraction of a new deck. Our prices for a 12 × 16 deck:
| New boards | Boards / sq ft | Labor / sq ft | Total / sq ft, old boards removed | 12 × 16 deck |
|---|---|---|---|---|
| Pressure-treated pine | $3.50 | $7 | $11–$16 | $2,200–$2,980 |
| Cedar | $5.50 | $7 | $13–$18 | $2,530–$3,420 |
| Composite | $11.50 | $12 | $23–$30 | $4,320–$5,850 |
| PVC | $12.50 | $12 | $23–$32 | $4,490–$6,070 |
If the frame is soft in more than a spot or two, or the ledger against the house is rotten, new boards would only hide the problem. That's a rebuild, and the deck cost calculator prices it.
Would composite last longer?
The boards, yes: composite makers estimate 25 to 30 years for their decking, and it needs no staining. But a composite deck normally sits on the same pressure-treated frame, so the frame still decides how long the whole deck lasts. The composite vs wood calculator compares what the two cost over the years.
Fair questions
Is cedar better than pressure-treated pine for a deck?
For the boards it's a matter of looks and budget: cedar is naturally rot-resistant and stays straighter, while treated pine costs less. For the frame and posts, treated lumber rated for the job is the norm, even under cedar boards.
Can an old deck be saved by staining it?
Stain protects sound wood. It won't fix rot, and it can hide it for a while. Check the frame with a screwdriver first, then decide.
How often should a deck be inspected?
A look every spring is a good habit: walk the boards, check the railing, and look underneath at the posts, the beams and where the deck meets the house.
Sources
- ForestSource, Pressure-treated wood: AWPA use categories: what UC3B, UC4A and UC4B mean, which parts of a deck each one is for, and how to read the end tag.
- USDA Forest Service, Protecting wood decks from biodegradation and weathering (Morrell, Schneider and Williams, 2001): a test of 32 deck finishes outdoors for over three years, and how long they held up.
- TimberTech, How long does decking last?: a composite decking maker's lifespan estimates for wood and composite decks.
- Hunker, What's the average lifespan of a wooden deck?: lifespan estimates for well-kept pressure-treated decks.
- American Wood Council, DCA 6: Prescriptive Residential Wood Deck Construction Guide: ledger attachment, joist spans, guards and stairs for wood decks.
- How we calculate: every suggested price behind this calculator, with the date it was last reviewed.
