Cedar vs Pressure-Treated Calculator
The DIY decking decision tool — pick a cedar grade (Western Red Clear / Select Knotty / STK or Northern White) against a PT tier (generic SYP, YellaWood, Wolmanized, Weather Shield). 10-dimension scoreboard: installed cost · 25-yr TCO · lifespan · decay class · insect resistance · splintering · heat retention · weight · IRC ground-contact · sustainability. Built on 2026-Q1 lumber-yard pricing + IRC 2021 R317 ground-contact rules. Cedar-boards-on-PT-joists is often the best-of-both — the calc flags it when deck height triggers IRC R317.1. Pairs with Cedar Deck Calculator (BoM) and PT Deck Cost Calculator (PT-only deep-dive).
Inputs
Deck dimensions
Scope
Head-to-head
Western Red Cedar — Select Knotty vs YellaWood SYP · 192 sqft · PA (Northeast, 1.22× labor)
Lower 25-yr TCO by $4,199 — install + maintenance. PT's chemical treatment delivers higher decay class (1 vs 2) and IRC ground-contact compliance, plus install costs ~20% lower than Western Red Cedar — Select Knotty.
- Install
- $11,894
- $/sqft
- $62
- Lifespan
- 22 yr
- 25-yr TCO
- $16,077
- Wins
- 2 dim
- Install
- $9,491
- $/sqft
- $49
- Lifespan
- 25 yr
- 25-yr TCO
- $11,878
- Wins
- 7 dim
10-dimension scoreboard
| Dimension | Cedar | PT | Winner |
|---|---|---|---|
Installed cost Real project cost for 192 sqft incl. boards, framing, fasteners, railing, stairs, finish, labor in Northeast. | $11,894 | $9,491 | PT |
25-yr TCO Install + 25 years of DIY maintenance + board-replacement reserve. Cedar yearly oil vs PT biennial seal + every-5-yr stain. | $16,077 | $11,878 | PT |
Expected lifespan Real-world service life with on-schedule maintenance. Skip maintenance and lifespan drops ~30%. | 22 yrs | 25 yrs | PT |
Decay resistance (AWPA class) Cedar relies on natural thujaplicins (oils) for decay resistance; PT relies on copper-based chemical treatment. PT chemistry is more aggressive — Class 1 (best) vs cedar's Class 2 (good). | Class 2 (natural) | Class 1 (chemical) | PT |
Insect resistance Cedar oils deter most insects but carpenter ants/bees may still bore. PT chemistry repels termites + carpenter ants reliably. | 7/10 | 9/10 | PT |
Splintering resistance Cedar's soft, straight-grain wood splinters far less than PT's denser SYP — better for kids + bare feet. | 8/10 | 6/10 | Cedar |
Heat retention (sunny 90°F) Cedar's lower density means lower thermal mass — slightly cooler than PT in direct sun. Both far cooler than dark composite. | +4°F | +0°F | PT |
Board weight Cedar ~25% lighter than PT. Matters for DIY install (easier carries, no chemical residue on skin) + load on substructure. | 2.4 lb/lf | 3.2 lb/lf | Cedar |
Ground-contact rated IRC R317.1 requires ground-contact-rated lumber within 6″ of grade. Cedar joists are not allowed below 6″ — must build on PT framing. PT is rated for direct contact. | No (above-grade only) | Yes (UC4A) | PT |
Sustainability Cedar has no chemical treatment (compostable end-of-life) but old-growth sourcing concerns. PT carries copper-based chemistry through to disposal — not recyclable, mild bioaccumulation in soil if buried. | 6/10 | 5/10 | Tie |
| Total dimension wins | Cedar 2·PT 7·tie 1 | ||
Tolerances applied to flag ties on trivial deltas. Decay-class score inverted (Class 1 = best in AWPA, scored as 5 in higher-is-better).
Cost breakdown (high estimate)
| Line item | Cedar | PT |
|---|---|---|
| Boards (waste +10%) | $2,534 | $991 |
| Fasteners | $355 | $182 |
| PT framing substructure | $1,440 | $1,440 |
| Railing | $1,520 | $1,040 |
| Stairs | $780 | $780 |
| Initial finish (year-0) | $317 | $288 |
| Labor (Northeast 1.22×) | $3,631 | $3,631 |
| Project install | $11,894 | $9,491 |
| 25-yr maintenance (DIY) | $3,600 | $2,160 |
| Board replacement reserve | $583 | $228 |
| 25-yr TCO total | $16,077 | $11,878 |
Both scenarios use PT pressure-treated substructure (joists, ledger, posts). Cedar always pairs with stainless fasteners (tannin reaction); PT modern MCA chemistry uses HDG; legacy ACQ generic also needs stainless. 2026-Q1 lumber-yard retail. Excludes permit, design fees, demolition.
How to use
Three steps. Permit-ready output.
- 01
Enter deck size + height
Length × width in feet plus shape (rectangle or L-shape — L-shape applies 0.85 area factor + 1.10 complexity premium on perimeter). Deck height in inches drives railing trigger (>30″ → guardrail per IRC R312.1) AND cedar ground-contact warning (<6″ from grade → cedar joists prohibited, PT required per IRC R317.1).
- 02
Pick a cedar grade
Western Red Cedar Clear ($8.50/lf, no knots, premium look, 25-yr life), WRC Select Knotty ($5.50, sound knots, mid-grade DIY favorite, 22-yr), WRC STK ($4.50, more knots, 18-yr life), or Northern White Cedar ($4.95, East-coast option, narrower boards). Premium clear is bookmatch joinery quality; STK is utility-deck quality. All cedars share the same maintenance schedule and decay/insect resistance profile.
- 03
Pick a PT tier
Generic SYP ($1.85/lf, no warranty, cheapest, often ACQ chemistry → needs stainless fasteners). YellaWood ($2.15, 25-yr warranty, MCA chemistry — HDG fasteners safe). Wolmanized ($2.10, 30-yr warranty — longest in industry, CA-C chemistry). Weather Shield ($1.99, 25-yr warranty, MCA). Branded PT is ~10-15% pricier than generic but delivers warranty + reliable end-tag stamping.
- 04
Project years + maintenance approach
TCO horizon 5-50 yrs. Toggle DIY vs professional maintenance — DIY is $0.45-0.75/sqft/yr at retail product cost; professional is $1.85-2.25/sqft/yr labor included. Cedar takes yearly Penofin/Sikkens oil + soap-wash; PT takes biennial Thompson's WaterSeal + every-5-yr stain refresh. Skip maintenance and cedar drops to ~12 yrs, PT to ~14 yrs lifespan.
- 05
Read the scoreboard + recommendation
10-dimension comparison: install cost · TCO · lifespan · decay class · insect resistance · splintering · heat · weight · ground-contact · sustainability. Tie-breaker is TCO when scoreboard is within 1. Watch the caveat for cedar-on-PT-substructure recommendation: cedar boards on PT joists is often the best-of-both at premium-cedar pricing minus the IRC ground-contact concern.
How we calculate
The math, fully transparent.
The Cedar vs Pressure-Treated Calculator is the DIY decking decision tool — pick a cedar grade (Western Red Clear / Select Knotty / STK or Northern White) against a PT tier (generic SYP, YellaWood, Wolmanized, Weather Shield), enter deck size + state, and get installed cost, 25-yr TCO, lifespan, and a 10-dimension scoreboard covering decay resistance, insect resistance, splintering, heat retention, weight, ground-contact compliance, and sustainability. Built on 2026-Q1 lumber-yard pricing + IRC 2021 R317 ground-contact rules. Pairs with the Cedar Deck Calculator (BoM) and PT Deck Cost Calculator (PT-only deep-dive).
IRC references
- IRC 2021 R317.1 — Decay-resistant lumber within 6″ of grade or in direct contact (PT required, cedar not rated)
- IRC 2021 R317.3 — Naturally durable woods (cedar, redwood, black locust) acceptable for non-ground-contact above 6″
- IRC 2021 R507.6 — Joist span tables (SYP allows longest spans; cedar shorter spans than SYP)
- IRC 2021 R312.1.1 — Guardrail required where walking surface >30″ above grade
- AWPA U1-23 — Use Categories for treated lumber (UC3B above-ground; UC4A ground-contact required for joists/ledger)
- ASTM D3345 — Wood preservation test for insect resistance
2026-Q1 retail. Cedar: WRC Clear $8.50/lf, WRC Select Knotty $5.50, WRC STK $4.50, Northern White $4.95. PT: Generic SYP $1.85, YellaWood $2.15, Wolmanized $2.10, Weather Shield $1.99. Cedar fasteners stainless required ($1.85/sqft); PT modern MCA HDG OK ($0.95/sqft); ACQ generic stainless required ($1.85/sqft). PT substructure $7.50/sqft same for both. Cedar railing $38/lf vs PT $26/lf. Stairs $195/step. Initial finish $1.65 cedar / $1.50 PT per sqft. Labor $11-20/sqft × regional multiplier. Maintenance DIY: cedar $0.75/sqft/yr, PT $0.45/sqft/yr; Professional: cedar $2.25, PT $1.85.
Both materials use same engine: board LF = area / 0.458 × 10% waste, then board × material $/lf + stainless/HDG fasteners ($0.95-1.85/sqft) + PT substructure ($7.50/sqft, same for both) + railing ($26 PT or $38 cedar /lf) + $195/step stairs + initial finish ($1.50 PT or $1.65 cedar /sqft year-0). Labor $11-20/sqft (wood install, no proprietary clips) × regional multiplier. 8% contingency on the high side.
Cedar: yearly Penofin/Sikkens UV oil application (~$0.55/sqft DIY material) + soap-wash. PT: biennial Thompson's sealer ($0.85/sqft / 2 yrs ≈ $0.43/sqft/yr) + every-5-yr full stain ($1.45/sqft / 5 ≈ $0.29/sqft/yr). Combined PT rate ~$0.45/sqft/yr DIY. Professional rates ~3-4× DIY (labor dominates).
Both materials lose ~20% of boards near end-of-life from cupping, splitting, or knot loss. Cedar STK (18-yr life) hits this reserve around year 14; WRC Select (22 yrs) at year 18; PT (~25 yrs) at year 21. We apply 1.15× inflation to original board cost since you'll replace 18-22 years from now.
10 dimensions evaluated. Cost/weight/heat → lower wins. Lifespan/decay/insect/splinter/sustainability/ground-contact → higher wins. Ground-contact is binary (yes/no). Tolerances: $50 install delta, $100 TCO, 1 lifespan yr, 1°F heat, 0.1 lb/lf weight, 1 point on 10-pt scales. Overall winner = majority of dimensions; ties broken by TCO.
Cedar lacks IRC ground-contact rating — joists within 6″ of grade must be PT UC4A minimum. Solution when picking cedar: use cedar BOARDS on PT JOISTS — perfectly code-compliant, gets the cedar aesthetic at PT's structural cost.
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