Wood vs Composite Deck: 25-Year Cost Calculator 2026

How wood vs composite is really compared

A deck is not bought once — it is bought, kept, and bought again. Wood is cheaper to build: $15.00 a square foot against $28.00 for composite at the defaults, so a 300 sq ft wood deck costs $4,500.00 to build and a composite one costs $8,400.00. But wood lasts 15 years and composite lasts 25, so over a 25-year horizon the wood deck must be built twice: once at the start and once at year 15, another $4,500.00. And wood costs $1.25 a square foot a year to keep — cleaning, sealing and staining — against $0.25 for composite, mostly washing. Over 25 years that is $9,375.00 of wood maintenance against $1,875.00 for composite. Add it up: wood $4,500.00 + $4,500.00 + $9,375.00 = $18,375.00; composite $8,400.00 + $0.00 + $1,875.00 = $10,275.00. Composite wins by $8,100.00, even though it costs $3,900.00 more on day one.

The replacement rule matters, so here it is plainly: a replacement is counted only when the replacement year is strictly less than the horizon. A wood deck with a 15-year life is replaced at year 15 only if the horizon is longer than 15 years — at a 15-year horizon there is no replacement, because the deck only needs replacing after the horizon ends. At a 30-year horizon the wood deck is replaced once, at year 15, and the composite deck is replaced once, at year 25 — a second wood replacement at year 30 is not counted, because year 30 is the end of the horizon, not inside it.

The worked example, line by line

Setup: deck 300 sq ft, wood $15.00/sq ft, composite $28.00/sq ft, horizon 25 years, wood life 15 years, composite life 25 years, wood maintenance $1.25/sq ft/yr, composite maintenance $0.25/sq ft/yr.

Line 1 — wood upfront. $15.00 × 300 = $4,500.00.

Line 2 — wood replacements. A 15-year deck is replaced at year 15, which is inside the 25-year horizon, so 1 replacement at $4,500.00.

Line 3 — wood maintenance. $1.25 × 300 × 25 = $9,375.00.

Line 4 — wood total. $4,500.00 + $4,500.00 + $9,375.00 = $18,375.00, which is $61.25/sq ft and $735.00/yr.

Line 5 — composite upfront. $28.00 × 300 = $8,400.00.

Line 6 — composite replacements. A 25-year deck is replaced at year 25, which is not inside a 25-year horizon, so 0 replacements.

Line 7 — composite maintenance. $0.25 × 300 × 25 = $1,875.00.

Line 8 — composite total. $8,400.00 + $0.00 + $1,875.00 = $10,275.00, which is $34.25/sq ft and $411.00/yr.

Line 9 — the winner. Composite wins by $18,375.00 − $10,275.00 = $8,100.00, despite costing $8,400.00 − $4,500.00 = $3,900.00 more upfront.

Reverse: the composite price that ties wood is $55.00/sq ft (exact 55.0000 — ($18,375.00 − $1,875.00) ÷ 300); the wood maintenance that ties composite is $0.17/sq ft/yr (exact 0.1700 — ($10,275.00 − $9,000.00) ÷ (300 × 25)); the horizon that ties the two is 13.0 years (exact 13.0000 — ($8,400.00 − $4,500.00) ÷ ($375.00 − $75.00)); the wood price that ties composite is $1.50/sq ft (exact 1.5000 — ($10,275.00 − $9,375.00) ÷ 600, unrealistically low); there is no area break-even, because both totals scale linearly with area; a $10,000 budget builds 291.97 sq ft of composite or 163.27 sq ft of wood, and a $15,000 budget builds 437.96 sq ft of composite or 244.90 sq ft of wood.

Every branch, checked

200 sq ft: wood is $12,250.00 and composite is $6,850.00 — composite wins by $5,400.00. A smaller deck costs less in total, but the per-square-foot figures are the same: $61.25 wood against $34.25 composite.

500 sq ft: wood is $30,625.00 and composite is $17,125.00 — composite wins by $13,500.00. The gap grows with the deck, because every extra square foot costs $61.25 in wood and $34.25 in composite over 25 years.

600 sq ft: wood is $36,750.00 and composite is $20,550.00 — composite wins by $16,200.00. At this size the $8,100.00 gap at 300 sq ft has doubled.

Wood $12/sq ft: wood falls to $16,575.00 — composite still wins by $6,300.00. Cheaper wood helps, but the replacement and the $9,375.00 of maintenance are still there.

Wood $20/sq ft: wood rises to $21,375.00 — composite wins by $11,100.00. Dear wood is dear twice over, because the replacement costs the same dear price.

Wood $25/sq ft: wood rises to $24,375.00 — composite wins by $14,100.00. At $25.00 a square foot, wood costs nearly as much as composite to build and far more to keep.

Composite $20/sq ft: composite falls to $7,875.00 — composite wins by $10,500.00. Cheap composite is the best of both worlds: the cheapest upfront and the cheapest to keep.

Composite $35/sq ft: composite rises to $12,375.00 — composite still wins by $6,000.00. Even at $35.00 a square foot, composite's low maintenance carries it.

Composite $40/sq ft: composite rises to $13,875.00 — composite still wins by $4,500.00. Composite has to reach $55.00 a square foot before wood catches it.

Wood life 25 years: wood needs no replacement, so it falls to $13,875.00 — composite still wins by $3,600.00. Even a wood deck that lasts the full horizon loses on maintenance alone: $9,375.00 against $1,875.00.

Wood life 10 years: wood needs two replacements, so it rises to $22,875.00 — composite wins by $12,600.00. A short-lived wood deck is the worst case: three builds in 25 years.

Wood maintenance $0.50/sq ft/yr: wood falls to $12,750.00 — composite still wins by $2,475.00. Wood maintenance would have to fall to $0.17 a square foot a year — almost nothing — before wood ties composite.

Wood maintenance $2.00/sq ft/yr: wood rises to $24,000.00 — composite wins by $13,725.00. A wood deck that is stained and sealed properly every year is an expensive deck to keep.

Composite maintenance $0.00/sq ft/yr: composite falls to $8,400.00 — composite wins by $9,975.00. Even if composite cost nothing to keep, the $8,400.00 upfront is the whole bill.

10-year horizon: wood is $8,250.00 and composite is $9,150.00 — wood wins by $900.00. This is the flip: over 10 years there is no wood replacement yet, so the cheaper build wins. Below a 13-year horizon, wood wins; above it, composite wins.

15-year horizon: wood is $10,125.00 and composite is $9,525.00 — composite wins by $600.00. At 15 years there is still no wood replacement — the replacement lands at year 15, which is the end of the horizon, not inside it — but 15 years of the maintenance gap is already enough for composite.

20-year horizon: wood is $16,500.00 and composite is $9,900.00 — composite wins by $6,600.00. At 20 years the wood deck has been replaced once, and the gap jumps.

30-year horizon: wood is $20,250.00 and composite is $19,050.00 — composite wins by only $1,200.00. At 30 years composite is finally replaced once, at year 25, so its bill jumps by $8,400.00 and the gap narrows sharply.

Reverse — the lines that matter: composite ties wood at $55.00/sq ft; wood maintenance ties composite at $0.17/sq ft/yr; the two tie at a 13.0-year horizon; wood ties composite at $1.50/sq ft, which no builder charges; there is no area break-even; and a $10,000 budget builds 291.97 sq ft of composite against 163.27 sq ft of wood.

The flip: at the defaults composite wins by $8,100.00. Wood wins only on a short horizon — 10 years, by $900.00 — because no replacement has happened yet. Once the horizon passes 13 years, composite wins, and it keeps winning until its own replacement at year 25 narrows the gap.

What the defaults assume

The model assumes the prices you enter, a wood deck life of 15 years and a composite deck life of 25 years, and flat maintenance of $1.25 a square foot a year for wood and $0.25 for composite. It assumes a replacement costs the same as the original build — check that, because demolition and disposal add to a rebuild. It assumes no discounting: a dollar in year 25 counts the same as a dollar today, so the totals are undiscounted cash costs, not present values. It leaves out the frame and footings, permits, railings and steps, and any resale value: a composite deck may add more to the home's value than a wood one, and that is not in the $18,375.00 or the $10,275.00. Rounding convention: money is rounded to cents, the break-even prices and horizon to two decimals with the exact value to four, and all figures are computed from unrounded values, rounded only for display.

Output · formula · meaning

Who uses this

• The homeowner choosing decking for a forever home: they learn composite wins by $8,100.00 over 25 years — so they know the dearer build is the cheaper deck, and they check the 13-year break-even horizon before deciding how long they will stay.
• The seller fixing up a house to sell in five years: they learn wood wins by $900.00 over 10 years — so they know the cheap build is the right call for a short stay, and they check the 15-year case at $600.00 the other way before committing.
• The builder pricing a big deck: they learn a 600 sq ft deck costs $36,750.00 in wood and $20,550.00 in composite over 25 years — so they know the gap is $16,200.00 at that size, and they check the $10,000 budget figures (291.97 sq ft composite, 163.27 sq ft wood) before quoting.
• The owner of a weather-beaten wood deck: they learn a 10-year wood life costs $22,875.00 over 25 years — so they know replacing it with composite saves $12,600.00, and they check the $2.00 maintenance case at $24,000.00 before staining it again.

Accuracy & limitations

The math is exact for the numbers you enter: each side is the upfront cost plus the replacements plus the maintenance, with replacements counted only when the replacement year falls strictly inside the horizon. What the model cannot do is know your prices: check the installed price per square foot, because composite ties wood at $55.00 a square foot and wood ties composite at $1.50 — and a real quote sits between them, where the answer is set by your maintenance and your horizon. It assumes a replacement costs the same as the original build and leaves out demolition, the frame and footings, permits, railings, steps, discounting and resale value. For the build cost alone, see deck cost calculator; for the same question about a deck or a patio, see deck vs patio cost.