Shed & Outbuilding Calculator

Estimate framing lumber, sheathing, siding, roofing materials, and total cost for any shed — gable, shed-roof, or gambrel.

Shed Dimensions

Width (ft)

Length (ft)

Wall Height

Roof Configuration

Roof Type

Roof Pitch

Siding & Floor

Siding Type

Floor Type

Openings

Windows

Doors

Floor Area

—

sq ft

—

Floor Area (sq ft)

—

Net Wall Area (sq ft)

—

Roof Area (sq ft)

—

Est. Total Cost

Key Quantities

— Studs

— 4×8 Sheets

— Shingle Bundles

⚠ Permit may be required

Full Materials List

Complete itemized materials based on your shed dimensions and configuration.

Cost Estimate

Adjust unit prices to match your local market. Totals update instantly.

Cost Breakdown

Permit & Code Thresholds

Most jurisdictions follow these general guidelines. Always verify with your local building department.

📄 Permit Requirements

Under 120 sq ft — Often permit-exempt (varies by jurisdiction)
120–200 sq ft — Permit commonly required; setbacks apply
Over 200 sq ft — Full permit + possible engineering review
Always check local zoning ordinances; HOA rules may be stricter
Some areas require permits for any permanent structure

📍 Setback Requirements

Rear yard — Typically 5–10 ft from property line
Side yard — Typically 3–5 ft from property line
Front yard — Usually not permitted in front setback
Corner lots have two "front" yards with stricter setbacks
Easements prohibit structures regardless of setbacks

🏗 Foundation Options

PT Skids — 4×6 or 6×6 pressure-treated timbers on gravel; easiest, relocatable
Concrete blocks — Solid or deck blocks on compacted gravel; good drainage
Concrete slab — Most permanent; requires rebar and forms; best for heavy use
Helical piers — Best for sloped sites; minimal site disturbance
All wood in contact with ground must be rated UC4B (ground contact)

🔧 Build Sequence

Prepare and level the site; install gravel pad
Set foundation skids or pour concrete slab
Frame and sheath the floor deck
Frame all four walls flat on the deck, then raise
Install temporary bracing; plumb and square walls
Frame the roof: ridge board, rafters, collar ties
Install roof sheathing (OSB or plywood)
Install felt paper + shingles or metal roofing
Install doors, windows, and trim
Apply siding and caulk all seams
Paint or stain exterior; install gutters if needed

📈 Roof Type Comparison

Gable — Classic triangle; good ventilation, easy to build, moderate attic space
Shed (lean-to) — Single slope; simplest build; attaches easily to house or fence
Gambrel — Barn-style; maximum interior headroom; more complex framing
Minimum pitch for asphalt shingles: 2:12 with underlayment; 4:12 preferred
Metal roofing works on pitches as low as 1:12 with proper sealant

🔌 Siding Guide

T1-11 — Economical; integral siding+sheathing in one panel; needs painting
LP SmartSide — Engineered wood; rot/impact resistant; pre-primed; ~20% premium
Vinyl — Zero maintenance; no painting; install over sheathing layer
Board & Batten — Vertical wood boards + narrow battens; rustic look; most labor
All siding requires 1" clearance above grade to prevent moisture wicking

How to Use This Calculator

Enter dimensions — Input width and length in feet. Wall height chips set the stud length used for framing calculations.

Choose roof type and pitch — Gable and gambrel roofs use the pitch multiplier; shed roofs use a simplified flat factor. Steeper pitch = more rafter material.

Select siding and floor — Siding type affects cost per sq ft; PT skids adds floor framing lumber to the materials list.

Enter openings — Each door subtracts 42 sq ft (6×7 opening) from wall area; each window subtracts 9 sq ft (3×3).

Check the Materials List tab — Full itemized list with quantities for ordering at the lumber yard.

Adjust prices in Cost Estimate — Override default unit prices with quotes from your supplier to get an accurate budget.

Key Formulas

Floor Area = Width × Length

Net Wall Area = (Perimeter × Height) − Door & Window Openings

Roof Area = Width × Length × Pitch Multiplier × 1.1 waste

Studs = 2 × (Long Wall + Short Wall) × 1.15

Sheathing Sheets = ⌈Total Area / 32⌉ (4×8 = 32 sq ft)

Shingle Bundles = ⌈Roof Squares × 3⌉ (3 bundles = 1 square)

Key Terms

Roof Square100 sq ft of roof surface. Shingles are sold by the bundle; 3 bundles cover 1 square for standard 3-tab shingles.

Pitch MultiplierFactor that converts horizontal floor area to actual sloped roof area. 6:12 pitch = 1.118 multiplier (hypotenuse/run).

T1-11 SidingGrooved plywood panel used as combined sheathing and siding. Available in 4×8 sheets (32 sq ft each).

PT LumberPressure-treated lumber chemically preserved against rot and insects. Required for all ground-contact applications.

OC (On-Center)Measurement from center of one stud to center of the next. Standard framing is 16" OC for sheds.

Gambrel RoofBarn-style roof with two slopes per side. Lower slope is steeper (typically 60°) creating usable loft space.

Rim BoardHorizontal board at the end of floor joists that caps the floor frame and provides a nailing surface for siding.

Ridge BoardHorizontal board at the peak of a gable roof. Rafters on both sides attach to it. Not a structural member in simple sheds.

Frequently Asked Questions

Do I need a permit for a small shed?

In most US jurisdictions, sheds under 120 sq ft are exempt from permits, though setback rules still apply. Some localities set the threshold at 100 or 200 sq ft. A 10×12 shed (120 sq ft exactly) is at the common threshold — check with your local building department. If your shed is 10×10 (100 sq ft), it is generally permit-free in most areas.

What size foundation do I need?

For sheds up to about 200 sq ft, pressure-treated 4×6 skids on a 4-inch compacted gravel pad are the most common and cost-effective foundation. Use at least three skids spaced evenly across the width. For larger sheds or areas with expansive soils, concrete piers or a full slab provide more stability and longevity.

How much does it cost to build a shed?

A basic 10×12 gable shed with T1-11 siding typically runs $800–$1,500 in materials for a DIY build. A 12×16 shed with LP SmartSide and metal roofing can run $2,000–$3,500 in materials. Contractor-built sheds of the same size typically cost $4,000–$8,000 installed. The Cost Estimate tab in this calculator uses current average lumber yard prices that you can adjust to your local quotes.

What roof pitch should I use?

A 6:12 pitch is the sweet spot for most sheds — it sheds water efficiently, provides some interior headroom under the roof, and is straightforward to frame. 4:12 is the minimum recommended pitch for asphalt shingles and reduces material cost slightly. 8:12 gives a steeper, more dramatic look but requires more rafter lumber. For lean-to roofs, even a 2:12 works with metal roofing.

Why does the calculator add 10–15% waste?

Lumber waste accounts for cuts, defects, and off-cuts that can't be reused. Sheathing waste (10%) covers edge cuts and damaged panels. Stud waste (15%) accounts for corner assemblies, headers over openings, and cripple studs. It's always better to order slightly more than to make a second trip to the lumber yard mid-project.