How much does a deck planter box cost in 2026?

For a 36×18×18 box (~5.4 cu ft soil): PT pine $80-110, western cedar $110-145, redwood $130-175, composite/PVC $145-195, IPE hardwood $185-265. Including soil ($25-40 per box) and liner ($5-10). DIY total: $90-275 depending on material. Contractor add ~$75-145 labor per box. Larger boxes (raised beds 6 ft long) run 2-3× these prices.

What's the best wood for a planter box?

Western red cedar is the best balance — naturally rot-resistant, food-safe (no chemical treatment), 18-yr lifespan, $5.80/BF. Redwood lasts longer (25 yr) but costs 25% more. IPE hardwood lasts longest (50 yr) but is heavy + slow to work. AVOID PT pine for edibles unless using a heavy plastic liner — modern ACQ treatment chemicals aren't immediately toxic but slow leaching into soil is a concern.

How much soil do I need for a planter box?

Inner dimensions × volume formula. Common boxes: 18×18×18 = 4.5 cu ft = 3 bags. 36×18×18 = 5.4 cu ft = 4 bags. 48×24×24 = 12.5 cu ft = 8-9 bags. 72×48×30 = 50 cu ft = 33+ bags (consider bulk delivery at $35-65/cu yd). 1 cubic yard = 27 cu ft = saves ~$50 vs bagged at this scale. The calculator outputs exact bag count.

Do I need a liner in my planter box?

Recommended for ALL wood planters. Heavy plastic (6-mil polyethylene) + landscape fabric prevents direct soil contact with wood interior. Extends wood lifespan 30-50% by reducing constant moisture exposure. REQUIRED if using PT wood with edibles. NOT needed for composite/PVC planters (no rot concern). Adds $5-15 per box depending on size.

How many drainage holes does a planter need?

½″ diameter holes at 6″ OC on the bottom. Calculator outputs count based on soil volume — typically 4-12 holes for most box sizes. Cover each hole with a square of landscape fabric to prevent soil washout. Add 1″ gravel/perlite layer above the holes for sustained drainage. Without proper drainage, roots rot within 1-2 seasons.

Can I use pressure-treated wood for vegetable planters?

ACQ-treated PT (post-2003) is considered safe for incidental contact but NOT directly for food-growing soil. Use a heavy plastic liner (6-mil polyethylene) to prevent soil contact with the treated wood — this is the standard recommendation from extension offices. Avoid older CCA-treated wood (pre-2003) entirely — it contains arsenic. Best practice: cedar, redwood, or IPE for edible planters.

Should I add casters to my planter box?

Only for freestanding boxes < 24″ wide that you want to move (chase the sun, store for winter, rearrange). Heavy-duty casters rated 100+ lb each ($38 kit). Soil weight: 80 lb/cu ft → a 4 cu ft soil-filled planter = 320 lb (80 lb per caster). Not for raised garden beds (too heavy + defeats the purpose). NOT for railing-mounted (no clearance).

How long does a cedar planter box last?

18 yrs typical with liner + drainage. Western red cedar's natural tannins resist rot + insects. Lifespan halved (8-10 yr) without liner because constant soil moisture eats away at the wood interior. Lifespan doubled (35+ yr) with: liner + raised on cleats (no ground contact) + annual cedar oil treatment + cover in winter. Cedar weathers to silver patina — don't bother staining.

Can I put a planter directly on my composite deck?

Yes with precautions: (1) use felt pad / composite spacers under the planter to prevent dye transfer from wet soil to composite, (2) drainage holes shouldn't pool water on composite surface — use a drain saucer or drainage pad, (3) verify deck framing supports the load (8 cu ft soil + plants ≈ 700 lb concentrated load — heavier than a typical patio chair). Most composite warranties cover planter use; check yours.

What size planter for vegetables?

Minimum 12″ deep for most vegetables (lettuce, herbs, beans). 18″ deep for tomatoes, peppers, root crops (carrots, beets). 24″ deep for deep-root crops (potatoes, parsnips). Width 18-24″ for most. Length flexible — many gardeners build long beds (4-6 ft) for vegetable rotation. Drainage critical for vegetables: roots rot fast in waterlogged soil. Use the Raised Garden Bed style preset for proper sizing.

4 styles · 5 materials · soil volume + lumber BoM · food-safe options

Planter Box Calculator

Q: How long does a cedar planter box last?

18 yrs typical with liner + drainage. Western red cedar's natural tannins resist rot + insects. Lifespan halved (8-10 yr) without liner because constant soil moisture eats away at the wood interior. Lifespan doubled (35+ yr) with: liner + raised on cleats (no ground contact) + annual cedar oil treatment + cover in winter. Cedar weathers to silver patina — don't bother staining.

Q: Can I put a planter directly on my composite deck?

Yes with precautions: (1) use felt pad / composite spacers under the planter to prevent dye transfer from wet soil to composite, (2) drainage holes shouldn't pool water on composite surface — use a drain saucer or drainage pad, (3) verify deck framing supports the load (8 cu ft soil + plants ≈ 700 lb concentrated load — heavier than a typical patio chair). Most composite warranties cover planter use; check yours.

Q: What size planter for vegetables?

Minimum 12″ deep for most vegetables (lettuce, herbs, beans). 18″ deep for tomatoes, peppers, root crops (carrots, beets). 24″ deep for deep-root crops (potatoes, parsnips). Width 18-24″ for most. Length flexible — many gardeners build long beds (4-6 ft) for vegetable rotation. Drainage critical for vegetables: roots rot fast in waterlogged soil. Use the Raised Garden Bed style preset for proper sizing.

Compute lumber, soil, liner, and total cost for a deck planter box across 4 styles (raised garden bed, freestanding box, railing-mounted, trough) × 5 materials (PT pine, western cedar, redwood, composite/PVC, IPE hardwood). Inputs: outer dimensions (length × width × height in inches), style, material, optional plastic liner, optional caster wheels (freestanding only), build quantity. Outputs: soil volume (cu ft + gallons), board feet of lumber needed per box, soil bags (1.5 cu ft each), drainage hole count (½″ holes at 6″ OC bottom), total material + labor cost. 5 material profiles with documented lifespan (PT 8 yr → IPE 50 yr) and rot resistance. Auto-warns: PT requires liner if growing edibles; dimensions outside recommended style ranges; lifespan tradeoffs across material comparison panel.

4 styles · 5 materialsSoil volume + lumber BoMFood-safety warningsDrainage holesFree forever

4 styles·Garden bed → trough

$80-265/box·PT → IPE 36″ range

8-50 yr·Lifespan by material

5 materials·Ranked at same scope

Inputs

Box dimensions (outer)

Lengthin

Widthin

Heightin

Soil volume / box5.4 cu ft (40 gal)

Lumber / box17.5 BF

Quantityea

Style4 styles

Wider footprint, taller for deep-root vegetables. Often paired with deck for backyard kitchen garden.

Materialrot resistance

Naturally rot-resistant. Food-safe (no chemical treatment). Premium aroma. 18-yr lifespan.

Install + region

State2-letter

Northeast · 1.22× labor

Raised garden bed

36×18×18″ · Western red cedar · 1× · diy

Project total

$159 – $174

$174/box · 10% contingency · 18-yr lifespan

3.4 DIY hr4 bags soil · 11 drain holes

Box specs (per unit)

Soil volume

5.4 cu ft

Soil (gal)

40 gal

Lumber

17.5 BF

Drainage holes

11 ea

Cost breakdown (all boxes)

Lumber (17.5 BF × 1× × $5.8/BF)	$102
Hardware (screws + brackets)	$18
Liner (6-mil poly + fabric)	$5
Soil (4 bags × $8.50)	$34
DIY (3.4 hr)	$0
Project total (high, +10%)	$174

Material comparison (same scope)

PT pineCHEAPEST$221 · 8yr · medium

Western red cedarPICKED$300 · 18yr · high

California redwood$334 · 25yr · high

Composite/PVC planter board$367 · 35yr · high

IPE tropical hardwood$517 · 50yr · high

Recommendations

▸ 18″ width is below Raised garden bed range (24-48″). Narrower box may not provide adequate root spread.
▸ PT pine (cedar look) is cheapest at $221 (saves $79 vs current). Trade-off: 8-yr lifespan vs 18-yr.

How to use

Three steps. Permit-ready output.

Enter outer dimensions

Length × Width × Height in inches. Standard sizes: raised garden bed 36×18×18 to 72×48×24, freestanding box 16×16×16 to 24×24×18, railing-mounted 36×8×10 to 48×12×12, trough 60×12×14 to 96×16×18. Calculator computes inner dimensions (outer − 2× board thickness) for soil volume.

Pick style + material

Style drives recommended dimension ranges + use cases. Raised garden bed for deep-root vegetables. Freestanding for portable accent plants. Railing-mounted for trailing flowers (verify load capacity of railing!). Trough for screen plants. 5 materials with documented lifespan + food-safety. PT cheapest but NOT food-safe without liner. Cedar/redwood/IPE food-safe.

Liner + casters

Liner: heavy plastic + landscape fabric inside the wood box. Doubles wood lifespan by preventing constant moisture contact. ALWAYS yes if growing edibles in PT box (chemicals). $0.95/cu ft soil volume. Casters: only for freestanding boxes — heavy-duty wheels rated 100+ lb each. Soil-filled planter weight = ~80 lb/cu ft.

Quantity

Number of identical planters to build. Batch-building saves 30-40% on DIY time (cut all sides, then bottoms, then assemble in parallel). Same scope across all boxes — for different sizes, run the calc separately. Multiple of same design = one shopping trip + parallel cuts.

Read soil + lumber output

Soil volume in cu ft + gallons + bag count (1.5 cu ft per bag @ $8.50). Lumber board feet (BF = 1 sqft × 1″ thick) → cost varies $2.45/BF (PT) to $12.50/BF (IPE). Drainage holes ½″ dia at the bottom of the box, count varies with soil volume. Material comparison panel shows cheapest option at your scope.

How we calculate

The math, fully transparent.

The Planter Box Calculator computes lumber, soil, liner, and total cost for a deck planter box across 4 styles (raised garden bed, freestanding box, railing-mounted, trough) × 5 materials (PT pine, western cedar, redwood, composite/PVC, IPE hardwood). Inputs: outer dimensions (length × width × height in inches), style, material, optional plastic liner, optional caster wheels (freestanding only), build quantity. Outputs: soil volume (cu ft + gallons), board feet of lumber needed per box, soil bags (1.5 cu ft each), drainage hole count (½″ holes at 6″ OC bottom), total material + labor cost. 5 material profiles with documented lifespan (PT 8 yr → IPE 50 yr) and rot resistance. Auto-warns: PT requires liner if growing edibles (chemicals not food-safe); dimensions outside recommended style ranges; lifespan tradeoffs across material comparison panel.

IRC references

No IRC code applies to standalone planter boxes
Railing-mounted planters: verify railing system rated for soil + plant weight (typically 50-100 lb per LF added load)
Composite deck protection: under planter use felt pad or composite spacers to prevent staining + moisture trap
Food-safety: PT lumber (post-2003 ACQ formulation) safe with liner; older CCA-treated wood NEVER safe for edibles

2026-Q1 retail pricing — Home Depot / Lowe's / cedar / redwood dealer averages. PT $2.45/BF, cedar $5.80/BF, redwood $7.20/BF, composite $8.50/BF, IPE $12.50/BF. Hardware $18/box. Caster kit (4 wheels) $38. Liner $0.95/cu ft soil volume. Potting soil 1.5 cu ft per bag at $8.50.

Soil volume

soilVolumeCuFt = (length - 2 × 1″) × (width - 2 × 1″) × (height - 1″) / 1728

Inner dimensions = outer minus 2× board thickness (sides) and 1× thickness (bottom only). 1 cubic foot = 1728 cubic inches. Convert to gallons via 7.481 gal/cu ft. Example: 36×18×18 outer → inner 34×16×17 = 9248 cu in = 5.4 cu ft = 40 gallons.

Soil bags needed

soilBagsPerBox = ceil(soilVolumeCuFt / 1.5)

Standard potting soil bag = 1.5 cu ft at ~$8.50 retail. For 5.4 cu ft volume = ceil(5.4 / 1.5) = 4 bags = $34 soil cost per box. Bulk potting soil cheaper if buying 10+ bags — many garden centers do $7/bag at scale.

Lumber board feet

BF = (2 sides + 2 ends + 1 bottom) sqft × (1″ thick) / 12 × 12 = surface_sqft × thickness_in/12 × 12

Board foot = 1 sqft × 1″ thick. For 36×18×18 box: sides 2×(34+2)×18/144 = 9 sqft, ends 2×16×18/144 = 4 sqft, bottom 36×18/144 = 4.5 sqft = 17.5 sqft total × 1″ thick = ~17.5 BF lumber per box. Cedar at $5.80/BF = $101 lumber per box.

Drainage holes

holeCount = max(4, ceil(soilVolumeCuFt × 2))

½″ diameter holes at ~6″ OC on the bottom. Minimum 4 holes regardless of size. Larger box = more holes for proper drainage. Some growers add a 1″ gravel layer at bottom to keep holes from clogging with soil. Cover holes with landscape fabric squares to prevent soil washout.

Total cost

total = (lumber + hardware + liner + soil) × quantity + labor; × 1.10 contingency

Per-box material breakdown. Hardware $18 (deck screws + corner brackets) + casters $38 if included. Liner $0.95/cu ft soil volume. Soil $8.50 per 1.5 cu ft bag. Labor varies $75-145/box (pro) by material complexity. DIY hours 2-3.5 per box × material multiplier. 10% contingency on subtotal.

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