How Much Does It Cost to Build a Deck in Washington State?

Average Deck Cost in Washington State

While every project is different, most professionally built decks in Washington fall within these general ranges:

• Basic wood deck: $35–$55 per square foot

• Composite deck: $55–$85+ per square foot

• Elevated or second-story deck: Higher due to posts, footings, bracing, and inspections

• Complex designs (stairs, multiple levels, custom railings): Higher due to labor and materials

These numbers reflect permitted, code-compliant construction, not unpermitted or surface-only work.

Why Deck Costs Vary So Much

Deck pricing is driven by more than size alone. A major factor is how the deck is supported and stabilized.

Many homeowners don’t realize that posts, footings, and bracing are often where problems — and costs — arise.

The following list is reproduced verbatim from a professional deck standards reference and highlights common structural issues that affect both safety and price:

Common deck post, footings, and bracing defects include the following:

1. Deck post is too tall.

2. Deck post is deteriorated or damaged.

3. Deck post is improperly secured, or is not secured, to the deck beam or to the deck footing.

4. Deck post is too far out of plumb.

5. Deck post is excessively bowed.

6. Deck post is not centered on the deck footing.

7. Deck footing is too small or not thick enough.

8. Deck footing is not deep enough.

9. Deck footing is made from improper materials, such as concrete blocks.

10. Deck footing is close to the house, but the bottom of the footing is not at the house footing level.

11. Deck bracing is absent.

12. Deck bracing is improperly installed.

Why This Affects Cost

Correcting or preventing these issues requires:

• Proper excavation and concrete footings

• Correct post sizing and attachment hardware

• Structural bracing for taller decks

• Additional inspections

These elements add cost — but skipping them creates safety risks and inspection failures.

Bracing and Structural Stability (Often Overlooked in Cheap Quotes)

Deck height has a direct impact on price. Taller decks require lateral bracing to prevent sway and collapse.

The following guidance is reproduced unchanged for accuracy:

Deck bracing should be installed between the corner deck posts and the deck beam. Deck bracing should not be attached to any interior deck posts. At least 2×4 lumber should be installed using ½-inch diameter screws with a washer on the head end. The brace should be about two feet beyond the post and about two feet below the beam.

What This Means for Homeowners

Bracing adds labor, hardware, and inspections — but it is required for safety. If a quote does not mention bracing on an elevated deck, that is a red flag.

Local Cost Factors: Seattle, Bellevue, and Sammamish

Seattle

• Permits are generally required for decks over 18 inches above grade or attached to the home

• Zoning, setbacks, and lot coverage can affect deck size and placement

• Steep lots and environmentally critical areas increase cost

Seattle decks often cost more due to permitting complexity and inspection requirements.

Bellevue

• Permits are typically required for decks 30 inches or more above grade or attached

• Electrical (lighting, outlets) adds inspection steps

• Soil and slope conditions often require deeper footings

Sammamish

• Structural deck work almost always requires a permit

• Decks over 18 inches are subject to lot coverage calculations

• Careful layout and planning are essential to avoid redesign costs

Materials and Long-Term Cost

Material choice affects not only upfront cost, but maintenance and lifespan.

A deck’s service life is a major cost consideration. The following explanation is reproduced verbatim:

The service life of a deck can be divided into two categories. One category is the service life of the deck components, such as the wood and the fasteners. The other category might be called functional obsolescence.

Deck component service life varies over a wide range that depends on factors including environmental conditions and maintenance.

A common estimate for the service life of an average deck, in an average environment, with average maintenance, is between 10 and 20 years.

Cost Implication

• Lower upfront cost may mean higher long-term replacement costs

• Composite decking costs more initially but reduces maintenance and extends usable life

Why Extremely Low Quotes Are Risky

Very low deck quotes often exclude:

• Permits and inspections

• Proper footings

• Required bracing

• Quality fasteners and connectors

These omissions can result in:

• Failed inspections

• Costly retrofits

• Safety hazards

Deck construction is not an area where cutting corners pays off.

Questions Homeowners Commonly Ask About Deck Costs

How much does a 12×16 deck cost in Washington?

Costs vary widely, but most professionally built decks of that size range from mid-four figures to well into five figures depending on height, materials, and site conditions.

Is it cheaper to repair an old deck?

Sometimes — but if posts, footings, or bracing are deficient, replacement is often safer and more cost-effective.

Does permit cost significantly affect pricing?

Permit fees are usually a small portion of total cost. The real cost impact comes from meeting the structural requirements those permits enforce.

Why do elevated decks cost more?

Elevation requires deeper footings, larger posts, bracing, and additional inspections.

Planning Questions to Ask Before Getting a Quote

Homeowners often start with questions like:

• Do I need a permit for my deck in my city?

• How high will my deck be above grade?

• What type of footings and bracing are required?

• What materials make sense for Washington’s climate?

• How long should this deck realistically last?

• What is included — and not included — in this quote?

Asking these questions early helps prevent surprises later.