Decks and Patios in Puget Sound: Costs, Materials and How to Hire
A new deck in the Seattle area costs $45 to $75 per square foot in cedar and $60 to $110 in composite, a paver patio $25 to $55 per square foot, and an attached covered patio $90 to $180. The difference between a deck that lasts and one that rots in a decade is mostly underneath it: footings, flashing at the house, and framing that is allowed to dry.
What decks and patios cost here
| Project | Installed range | Notes |
|---|---|---|
| Cedar deck, ground level | $45 – $75 per sq ft | Lowest upfront cost; needs oiling |
| Composite or PVC deck, ground level | $60 – $130 per sq ft | Board line drives the range |
| Elevated or second-story deck | Add 30% – 80% | Tall posts, bracing, engineering |
| Railing | $70 – $450 per linear ft | Cedar low end; glass high end |
| Paver patio | $25 – $55 per sq ft | Base depth and paver type |
| Covered patio, attached roof | $90 – $180 per sq ft | Roof style, ceiling, heaters |
| Deck repair: boards, posts, ledger | $1,500 – $15,000 | Depends on what is rotted |
Cedar or composite in a wet climate
Western red cedar is cheaper to build and looks and feels like wood, but it needs a penetrating oil every two to three years here and wears out fast in deep shade on low decks. Capped composite and PVC cost more but do not rot, need only washing, and handle damp shade far better. In full sun with good airflow and an owner who refinishes it, cedar remains a sound choice. The deck or patio guide helps decide between a raised deck and a ground-level surface in the first place.
The framing details that decide lifespan
- Ledger flashing. The board that bolts the deck to the house must be flashed so water does not run behind it and rot the house's rim joist. Ledger failures cause most deck collapses.
- Joist protection. Tape on the tops of joists and beams keeps water that drips through board gaps from sitting in the wood.
- Footings. Concrete footings below the frost line on undisturbed soil, with posts on metal bases rather than buried.
- Lateral connection. Elevated decks need hardware tying them to the house floor framing and bracing so they do not sway.
- Airflow. The lower and more enclosed the deck, the slower it dries.
Paver patios on clay soil
Much of the region sits on clay and glacial till that drain slowly. A patio that stays flat needs 8 to 12 inches of excavation, fabric over soft soil, compacted crushed rock in layers and a slope away from the house. Permeable pavers let rain soak through and can help on lots near their impervious-surface limit.
Deck and patio permits
Decks more than 30 inches above grade at any point, attached decks, decks over 200 square feet and decks serving an exit door generally need a permit, as do covered patios and decks carrying hot tubs. Ground-level patios usually do not, though large new hard surfaces can trigger stormwater review. Check with the Permit Checker.
How to vet a deck builder
- Confirm L&I registration, bond and insurance.
- Ask how the ledger will be attached and flashed, and whether they will open the siding to do it.
- Ask about joist tape, footing depth and post bases.
- For composite, ask whether they install to the manufacturer's specifications, which warranties depend on.
- Ask who prepares and pulls the permit on raised or covered decks.
- Ask for a written warranty on workmanship separate from the material warranty.
Deck quote red flags
- No mention of the ledger or flashing on an attached deck.
- New boards over old framing without an inspection of the framing.
- Composite joist spacing at 24 inches.
- No permit on a deck several feet above the yard.
- Railing posts attached with a few screws into the rim joist.
Deck and patio guides by city
Questions about decks and patios
How long does a deck take to build?
One to two weeks on site for most decks, after any permit.
Can new boards go on my old framing?
Only if the framing is sound and spaced for the new boards. Older framing is often rotted at the ledger.
Do composite decks get slippery?
Wet surfaces with moss or leaves on them are slippery whatever the material. Capped composite has texture and cleans more easily than mossy cedar.
Can I build a covered patio over my deck?
Usually, with new footings for the roof posts and a permit.
How often should a deck be inspected?
Every few years for ground-level decks, more often for elevated decks or any deck older than twenty years.