A 14 by 20 deck covers 280 square feet, and the shorter dimension drives more of the price than the square footage suggests. Deck installation on that footprint runs roughly $9,000 to $15,000 in pressure treated material and $16,000 to $26,000 in capped composite across the Puget Sound region. The 14 foot span, the permit threshold, and stock board lengths explain most of the variation.
The 14 Foot Direction Sets the Framing Bill
Joists running the 14 foot direction hit a hard limit under Washington load rules. State code calculates deck framing at 60 pounds per square foot of live load, which shortens allowable spans against the national tables.
Douglas fir and hem fir joist limits at 60 psf:
- 2×8 at 16 inches on center: 9 feet 5 inches
- 2×10 at 12 inches on center: 13 feet 3 inches
- 2×12 at 16 inches on center: 13 feet 4 inches
- 2×12 at 12 inches on center: 15 feet 4 inches
Only the last option clears 14 feet in a single run. Every other layout needs an intermediate beam splitting the span, which adds posts and footings but allows smaller joists.
Two Framing Paths, Two Price Points
The choice between one long span and two short ones changes the material list, and SmartDecks prices both when the site allows either.
Single span with 2×12 joists at 12 inches on center:
- More lumber per square foot, roughly 25 percent more joist material
- Fewer footings, usually six to eight
- Clear space underneath with no mid run posts
- Adds $900 to $1,600 over the alternative
Split span with a center beam and 2×8 joists:
- Smaller joists at wider spacing
- Two additional footings and posts
- Lower material cost, higher labor hours
- Better fit on sloped lots where post height varies anyway
Ledger Fasteners Tighten With the Span
The house connection scales with joist length. At a 14 foot span under the state load figure, fastener spacing runs far tighter than most homeowners expect:
- Half inch lag screws: 9 inches on center
- Half inch through bolts: 13 inches on center
- Both patterns staggered top and bottom along the ledger
- Flashing above the ledger required in every case
A 20 foot ledger at 9 inch spacing takes roughly 27 lag screws. Hardware and labor for that connection alone runs $250 to $450, and the framing stage is where a low bid usually cuts corners.
280 Square Feet Crosses the Permit Line
Kent exempts a deck from permitting only when it stays under 200 square feet, sits no more than 30 inches above grade, stands free of the house, and does not serve a required exit door. Those permit exemption rules put a 280 square foot build outside the exemption on size alone.
Permit stage costs and timing:
- Application and plan review: $250 to $700 in most King County jurisdictions
- Site plan with dimensions and setbacks required at submittal
- Footing inspection, then framing inspection before decking goes down
- Review time of two to four weeks before construction starts
Stock Board Lengths Favor This Size
A 14 by 20 layout wastes less material than most rectangles, which holds the per square foot cost down.
How the lengths work out:
- Capped composite decking sells in 12, 16, and 20 foot boards, so the 20 foot direction runs with no butt joints
- Pressure treated decking in 16 foot lengths covers the 14 foot direction with two feet of trim waste per board
- Joists at 14 feet come out of 16 foot stock
- A 20 foot ledger and 20 foot beams cut cleanly from standard lengths
Butt joints matter beyond appearance. Every seam needs blocking underneath and creates a spot where water sits, so a layout that avoids them lowers both cost and long term maintenance.
What the 280 Square Feet Actually Buys
Component pricing on a typical Kent build:
- Footings and posts: $1,200 to $2,600
- Framing package including ledger hardware: $3,000 to $4,800
- Pressure treated decking: $1,100 to $1,900
- Capped composite decking with hidden fasteners: $4,200 to $7,500
- Railing at 34 linear feet on an open sided deck: $2,400 to $4,800
- Stairs at four risers: $700 to $1,200
Railing is the line most often left out of a rough deck installation estimate. A ground level 14 by 20 with no guardrail lands near the bottom of the range, while the same footprint at five feet carries railing on three sides.
Comparing a 14 by 20 to a 20 by 20
Adding six feet of width raises the footprint by 43 percent, and price rises less than that.
Where the economies show up:
- Ledger and house connection labor stays identical
- Permit and mobilization costs do not change
- Crew days rise by one or two, not by half
- Per square foot cost typically drops $3 to $6 on the larger build
Homeowners weighing the two sizes often find the wider deck costs less per usable square foot, though a 14 foot depth still holds a table with chairs pulled out, which is the practical test most yards need.
Timeline and Crew Days
Deck installation on 280 square feet moves faster than the permit process that precedes it.
Typical schedule once permits clear:
- Demolition of an existing structure: half a day to one day
- Footings and cure time: one to two days
- Framing and inspection: two days
- Decking, railing, and stairs: two to three days
Weather adds days between November and April, since footings poured into standing water fail inspection. SmartDecks crews schedule concrete work around the forecast rather than the calendar during those months.
Upgrades That Move the Final Number
Base pricing assumes an open deck with a simple railing. Common additions and their range on this size:
- Integrated lighting on posts and stairs: $900 to $2,200
- Steel framing instead of wood: adds $2,200 to $3,400
- Cable or glass railing instead of aluminum balusters: adds $2,000 to $4,500
- Built in bench seating along one side: $1,400 to $2,800
- Under deck drainage for storage below: $2,400 to $4,000
Each item is easier to install during the original build than to retrofit later, which is why quotes from a deck company working across King and Pierce counties tend to list them as line items rather than folding them into a single figure.
Narrowing a 14 by 20 Quote to One Number
Pricing for deck installation on this footprint firms up once three things are settled: joist direction, deck height, and railing material. Those three decisions account for most of the spread between a $10,000 quote and a $24,000 one, and none of them can be answered from a satellite image.
For a 280 square foot deck, an on-site assessment is the most reliable way to determine the final cost and construction requirements. A typical evaluation includes the span layout, footing count, applicable permit requirements, and a detailed material list that specifies the framing, decking, and railing components.
