DIY vs Hire Deck Building: Cost Comparison Calculator

Is $5,300.00 the right DIY cost for building a 400 sq ft deck?

On the defaults — 400 square feet at $8.00 of materials each, $300.00 of supplies and 40 hours of your time at $45.00 an hour — building the deck costs $5,300.00 to do yourself, against a $10,000.00 pro cost, so DIY wins by $4,700.00. The DIY cost is the square feet times the materials per square foot plus the supplies plus your hours valued at your hourly rate; the pro cost is the square feet times the pro price per square foot. A pro deck build is usually priced per square foot — and a typical backyard deck is 300–500 square feet. Pressure-treated pine installed by a pro usually runs $15–$25 per square foot, cedar or redwood $20–$35, and composite $25–$45, so a 400 sq ft pro job commonly lands between $6,000 and $14,000 depending on the material and the site.

Four things about the model are worth stating plainly. First, the materials are $8.00 a square foot — 400 square feet is $3,200.00 of decking. Second, the DIY cost is $5,300.00 — $3,200.00 of materials + $300.00 of supplies + 40 × $45.00 of your time. Third, the pro cost is $10,000.00 — 400 × $25.00 a square foot. And fourth, DIY wins by $4,700.00 — but the answer turns on your hourly value: at $163.00 an hour hiring wins; all listed in Accuracy & limitations.

The worked example, line by line

Setup: 400 square feet at $8.00 of materials each, $300.00 of supplies, 40 hours at $45.00 an hour, pro price $25.00 a square foot.

Line 1 — the DIY cost. The DIY cost is 400 × $8.00 + $300.00 + 40 × $45.00 = $5,300.00.

Line 2 — the pro cost. The pro cost is 400 × $25.00 = $10,000.00.

Line 3 — the winner. $10,000.00 − $5,300.00 = $4,700.00 — DIY wins by $4,700.00.

Line 4 — the check. $3,200.00 + $300.00 + $1,800.00 = $5,300.00, the DIY cost; and $5,300.00 + $4,700.00 = $10,000.00, the pro cost.

Every branch, checked

Hours 20: DIY $4,400.00; pro $10,000.00 — DIY wins by $5,600.00 — With 20 hours the DIY cost is $4,400.00 — DIY wins by $5,600.00.

Hours 60: DIY $6,200.00; pro $10,000.00 — DIY wins by $3,800.00 — With 60 hours the DIY cost is $6,200.00 — DIY wins by $3,800.00.

Materials $5.00 per square foot: DIY $4,100.00; pro $10,000.00 — DIY wins by $5,900.00 — With $5.00 of materials a square foot the DIY cost is $4,100.00 — DIY wins by $5,900.00.

Materials $15.00 per square foot: DIY $8,100.00; pro $10,000.00 — DIY wins by $1,900.00 — With $15.00 of materials a square foot the DIY cost is $8,100.00 — DIY wins by $1,900.00.

Hours 80: DIY $7,100.00; pro $10,000.00 — DIY wins by $2,900.00 — With 80 hours the DIY cost is $7,100.00 — DIY wins by $2,900.00.

Materials $19.75 per square foot: DIY $10,000.00; pro $10,000.00 — exact tie — With $19.75 of materials a square foot the DIY cost is $10,000.00 — a dead heat, a TIE, not a hiring win.

Hours 30: DIY $4,850.00; pro $10,000.00 — DIY wins by $5,150.00 — With 30 hours the DIY cost is $4,850.00 — DIY wins by $5,150.00.

The reverses, worked backwards

Smallest whole-dollar hourly value where hiring WINS: At the displayed $163 the figures are DIY $10,020.00; pro $10,000.00 — Hiring wins by $20.00. At the displayed $163 the DIY cost is $10,020.00 and hiring wins by $20.00. At $162 the DIY cost is $9,980.00 and DIY wins by $20.00 — so $163 is the smallest whole-dollar hourly value where hiring wins.

Largest whole-dollar hourly value where DIY still wins by at least $500.00: At the displayed $150 the figures are DIY $9,500.00; pro $10,000.00 — DIY wins by $500.00. At the displayed $150 the DIY cost is $9,500.00 and DIY wins by $500.00. At $151 the DIY cost is $9,540.00 and DIY wins by only $460.00 — below $500 — so $150 is the largest whole-dollar hourly value where DIY still wins by at least $500.00.

Smallest whole-dollar supplies where hiring WINS: At the displayed $5,001 the figures are DIY $10,001.00; pro $10,000.00 — Hiring wins by $1.00. At the displayed $5,001 the DIY cost is $10,001.00 and hiring wins by $1.00. At $5,000 the DIY cost is $10,000.00 — a dead heat, a TIE, not a hiring win — so $5,001 is the smallest whole-dollar supplies where hiring wins.

Smallest whole-cent materials per square foot where hiring WINS: At the displayed $19.76 the figures are DIY $10,004.00; pro $10,000.00 — Hiring wins by $4.00. At the displayed $19.76 the DIY cost is $10,004.00 and hiring wins by $4.00. At $19.75 the DIY cost is $10,000.00 — a dead heat, a TIE, not a hiring win — so $19.76 is the smallest whole-cent materials per square foot where hiring wins.

Smallest whole-hour hours where hiring WINS: At the displayed 145 hours the figures are DIY $10,025.00; pro $10,000.00 — Hiring wins by $25.00. At the displayed 145 hours the DIY cost is $10,025.00 and hiring wins by $25.00. At 144 hours the DIY cost is $9,980.00 and DIY wins by $20.00 — so 145 hours is the smallest whole-hour hours where hiring wins.

Smallest whole-dollar pro price per square foot where DIY wins at all: At the displayed $14 the figures are DIY $5,300.00; pro $5,600.00 — DIY wins by $300.00. At the displayed $14 the pro cost is $5,600.00 and DIY wins by $300.00. At $13 the pro cost is $5,200.00 and hiring wins by $100.00 — so $14 is the smallest whole-dollar pro price per square foot where DIY wins at all.

A note on the ties: at $19.75 of materials a square foot the DIY cost is $10,000.00 — exactly the pro cost — so it is a dead heat, not a hiring win; hiring only wins at $19.76. The same holds for supplies: at $5,000.00 the DIY cost is $10,000.00, a dead heat, and hiring only wins at $5,001.00. One more edge: with 250 square feet, materials of $12.375, supplies of $215.75, 18.5 hours at $42.25 an hour and a $28.50 pro price, the DIY cost is 4091.125 unrounded — shown as $4,091.13 after rounding — and DIY wins by 3033.875 unrounded — shown as $3,033.88 after rounding. With materials at $30.00 a square foot, supplies of $500, 60 hours at $75.00 an hour and a $20.00 pro price, the DIY cost is $17,000.00 — pro wins by $9,000.00.

What the defaults assume

The defaults are 400 square feet at $8.00 of materials each, $300.00 of supplies, 40 hours at $45.00 an hour and a $25.00 pro price per square foot — DIY $5,300.00; pro $10,000.00 — DIY wins by $4,700.00. With Hours 20, DIY $4,400.00; pro $10,000.00 — DIY wins by $5,600.00. With Hours 60, DIY $6,200.00; pro $10,000.00 — DIY wins by $3,800.00. With Materials $5.00 per square foot, DIY $4,100.00; pro $10,000.00 — DIY wins by $5,900.00. With Materials $15.00 per square foot, DIY $8,100.00; pro $10,000.00 — DIY wins by $1,900.00. With Hours 80, DIY $7,100.00; pro $10,000.00 — DIY wins by $2,900.00. With Materials $19.75 per square foot, DIY $10,000.00; pro $10,000.00 — exact tie. With Hours 30, DIY $4,850.00; pro $10,000.00 — DIY wins by $5,150.00. With Square feet 0, materials $0, supplies $0, hours 0, hourly value $0, DIY $0.00; pro $0.00 — exact tie. With Square feet 100, materials $10.00, supplies $50, hours 5, hourly value $30, pro $20.00 per square foot, DIY $1,200.00; pro $2,000.00 — DIY wins by $800.00. With Square feet 250, materials $12.375, supplies $215.75, hours 18.5, hourly value $42.25, pro $28.50 per square foot, DIY $4,091.13; pro $7,125.00 — DIY wins by $3,033.88. With Materials $30.00 per square foot, supplies $500, hours 60, hourly value $75, pro $20.00 per square foot, DIY $17,000.00; pro $8,000.00 — Hiring wins by $9,000.00. With Hours 0, DIY $3,500.00; pro $10,000.00 — DIY wins by $6,500.00. With Hours 12.5, DIY $4,062.50; pro $10,000.00 — DIY wins by $5,937.50. With Win-by bars — DIY $5,300.00, hourly value for a $500.00 DIY win $150.00; pro price per square foot for a $1,000.00 DIY win $15.75; materials per square foot for a $1,000.00 DIY win $17.25.

Output · formula · meaning

Who uses this

• The homeowner building a 400 sq ft deck: they learn building it costs $5,300.00 to do themselves against a $10,000.00 pro cost — and they check the $163 reverse to see where hiring takes over.
• The homeowner whose time is pricey: they learn at $150.00 an hour DIY wins by $500.00 — and they check the $14 reverse to see how low the pro price must fall before hiring wins.
• The homeowner facing a $19.76 materials bill: they learn hiring wins by $4.00 at that materials cost — and they check the $19.75 tie to see that one cent less is a dead heat, not a hiring win.
• The homeowner with a 145-hour job: they learn at 145 hours hiring wins by $25.00 — and they check the $5,001 reverse to see how much supplies must cost before hiring wins.

Accuracy & limitations

The math is first-principles: the DIY cost is the square feet times the materials per square foot plus the supplies plus the hours times the hourly value; the pro cost is the square feet times the pro price per square foot; the winner is the lower total. The reverses are judged on the UNROUNDED totals: at $19.75 of materials a square foot the DIY cost is $10,000.00, exactly the pro cost, so it ties; at $19.76 the DIY cost is $10,004.00, so hiring wins by $4.00. The same rounding shows in the fractional edge: the DIY cost is 4091.125 unrounded, shown as $4,091.13 after rounding, and the win is 3033.875 unrounded, shown as $3,033.88 after rounding. What the model cannot do is price your deck: the $15–$25 pressure-treated pine, $20–$35 cedar or redwood and $25–$45 composite per-square-foot pro ranges and the $6,000–$14,000 full-deck range are typical figures, not quotes; footings that are too shallow heave in winter, railings that are too low or too far apart fail inspection, a deck that is not level or not properly flashed against the house rots the framing, and a big deck takes a pro crew days but a DIYer several weekends — are the risks of doing it yourself; and the hourly value is yours to set — an hour of a Saturday is not worth the same to everyone. A deck is worth building yourself when it is small and low to the ground, the design is a simple rectangle, and you have a helper — boards are long and awkward alone, and a second pair of hands halves the time. A pro is worth it for a raised or second-story deck, composite decking (special fasteners and expansion gaps), tight deadlines, or when the permit and inspection process matters — most pro jobs carry a labour warranty the DIY route does not. Use it to see which side wins on your numbers — then get a real quote before you book.

Frequently asked questions