MyBuildPlanner / Calculators / Decks & Structures

Deck, Shed & Outdoor Structure Cost Calculators

Size it, foot it, permit it — then price the material.

By Trace Bailey · Reviewed August 8, 2026 · How we calculate

16 calculators

Decks & Structures

Everything in this category carries load the same way: down through posts or a slab into soil. That's why a deck, a carport and a shed fail at the same three places — footing depth, member span, and the metal tying one piece to the next. Nail those and the rest is carpentry you can learn as you go. Miss one and the structure racks, heaves or pulls away from the house, usually in its second winter.

Settle three things before you open any calculator: the footprint, the height off grade, and whether the structure is permanent. Those set your footing depth, your permit status and most of your bill — the material list just follows from them. Every tool here prices material at national-average retail and shows a fifteen percent spread; none of it is labor. A contractor's bid for the same work usually lands near three times the number.

Before you pick a tool

Decide these before you open a calculator

How big should my deck actually be?

Furniture sets the number, not the house wall. A table for six with the chairs pushed back needs a clear ten by ten feet, a grill wants four feet of open depth in front of it, and a walking lane is 36 inches. Add those up and 12 by 16 feet is the smallest deck that does both jobs without traffic crossing the table. Depth matters more than length: under 10 feet a deck behaves like a walkway. Commit to 12 to 14 feet of depth, which puts you on 2x10 joists at 16 inches on-center in the Deck Builder, and let the house wall set the length.

Do I need footings below the frost line, or will deck blocks do?

Anything bolted to the house or holding up a roof gets poured piers, dug six inches past the frost line — the Deck Builder adds that six inches to the frost depth you enter. Figure 48 to 60 inches across northern New England, Minnesota and the Dakotas; 42 around the Great Lakes; 30 to 36 through the Ohio Valley and Mid-Atlantic; 12 to 24 in the mid-South; effectively none on the Gulf. Precast blocks are honest only under a freestanding ground-level platform or a shed on skids, which ride an inch of heave and settle back. A ledger cannot: the house holds still, the deck lifts, the connection tears.

Ground level or raised — what does 30 inches actually change?

Thirty inches above grade is where the money changes, not just the code. Below it you generally owe no guard at all. Above it you owe a 36-inch guard with gaps a 4-inch ball will not pass, 6x6 posts once the deck clears 48 inches, and a permit almost everywhere. Switching railing on in the Deck Builder adds roughly $20 a linear foot in pressure-treated material, about a quarter of a small deck's bill, and a composite or aluminum kit runs three to four times that. If your grade lets you land under 30 inches, take it; if not, lay the flight out in the Stairs Builder.

Pergola, carport, shed or garage — which do I actually want?

Pick by what you are protecting. A pergola defines a patio and cuts glare but stops no weather, and at roughly $14 to $19 a square foot in cedar it is the cheapest and fastest structure here. The carport is the value buy: on the same 20 by 20 footprint the Carport Builder lands near $2,200 in material against about $7,800 in the Garage Builder, so unless you need a lockable, insulable room, take the carport. A shed is enclosed storage on skids or a slab. A garage means a slab, engineered trusses and inspections. Price whichever roof you land on in the Roofing Calculator.

Reference

Outdoor structures compared — DIY material cost per square foot, what it sits on, and permit odds

Structure	Common size	DIY material cost	Sits on · permit
Pergola	12 × 10 ft	$14–19/sq ft (cedar)	Piers · sometimes
Ground-level deck, no guard	12 × 16 ft	$8–11/sq ft (PT)	Piers or blocks · sometimes
Raised deck, stairs + guard	14 × 20 ft	$10–14/sq ft (PT)	Piers below frost · nearly always
Carport	12 × 20 ft	$7–11/sq ft	Piers below frost · nearly always
Shed	10 × 12 ft	$20–30/sq ft	Skids or slab · often exempt
Detached garage	24 × 24 ft	$14–21/sq ft	Slab + thickened edge · always

Material only, taken from each builder on this site at its default options, including the fifteen percent spread those tools apply. Swapping PT decking for composite adds about half again to the two deck rows. Nothing here includes labor, permit fees, electrical or interior finish — hiring the same work out typically lands near three times these figures.

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Other calculator categories

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Answers

Frequently asked questions

I'm building more than one of these — what order?

Do all the digging and concrete in one trip. Footings for a deck, a pergola and a shed pad are the same operation, and renting an auger once beats renting it three times. One sequence is not optional: if a pergola is going over a deck, its posts run through the deck frame to their own footings. Block those penetrations out while you frame, then build up — a pergola lag-bolted to decking racks in the first real wind. Roofing, siding and finishes come last, after everything that needed a shovel has cured.

How close to the property line can I build?

Setbacks decide your footprint more often than the calculator does. Typical residential zoning holds accessory structures 5 to 10 feet off the rear line and 3 to 5 feet off the side, and many towns cap lot coverage — the share of the lot under roof — near 30 to 40 percent. An attached deck usually counts toward that; a ground-level deck under 30 inches sometimes does not. Utility easements along the back of a lot can be off-limits entirely, even inside the setback. Pull your plat, call the zoning desk before you buy lumber, and check the HOA separately — it can be stricter than the town.

Why is a contractor's quote three times the calculator's total?

Because these tools price material and a bid prices labor, and labor is the bigger half. Across this category materials land around 30 to 40 percent of an installed price: a 24 by 24 garage that totals near $9,700 in material in the Garage Builder is commonly bid around $30,000 finished. The rest is crew hours, mobilization, permit runs, insurance, warranty and margin — that is what a trade costs, not padding. Use these totals to check the material line on a bid and to decide what to sub out. The slab pour and the roof are the two worth paying for.

What lumber grade and fasteners does outdoor framing need?

Anything buried, within six inches of soil, or sitting on concrete needs ground-contact pressure-treated stock — AWPA use category UC4A. That covers posts, skids and sill plates. Above-ground treated, UC3B, is fine for joists, beams, rails and stringers. Cedar, redwood and composite are surface materials; do not frame with them. The fastener rule catches people out: copper-based treatments, ACQ especially, eat plain zinc, so every screw, hanger, bolt and connector touching treated wood must be hot-dip galvanized or stainless. Keep one metal through a whole connection — stainless screws in galvanized hangers set up galvanic corrosion.