18x18 Shed Material List
Quick Answer
An 18x18 gable shed with 8 ft walls, 16 inch on center framing, 4/12 roof pitch, pressure treated floor framing, OSB or plywood sheathing, a basic double door, and gravel foundation is a very large backyard structure often used as a full workshop, small garage, vehicle storage, or major hobby space. The 18 ft span pushes standard dimensional lumber to its limits and requires heavy framing. This size approaches the scale of a small detached garage.
See all shed material lists by size
You will need:
- Very heavy pressure treated lumber for the floor system
- 2x4 wall framing
- 2x8 to 2x10 roof framing
- Extensive floor, wall, and roof sheathing
- Panel or lap siding
- Asphalt shingles and underlayment
- Reinforced double door framing
- Large quantities of fasteners and hardware
Realistic 2026 total material cost: $8,500 to $13,500
This assumes a gravel base and basic exterior finishes only.
Need a smaller option? See our 16x20 shed material list. Want a larger build? See our 12x28 shed material list.
Full Material List
Quantities assume 8 ft wall height, 16 inch on center spacing, and a standard double door on one side.
Floor Framing
An 18 ft span is beyond what smaller joists can handle. Heavy members are required.
Gravel Base
- 8 to 11 cubic yards of compacted 3/4 inch crushed gravel
Floor Frame (Pressure Treated)
Perimeter
- 2x12x18 PT – 4 (rim and band joists)
Floor Joists (16 inch OC across 18 ft span)
- 2x12x18 PT – 13 to 14
Note: Some builders use doubled 2x10s, beams, or intermediate supports instead.
Floor Sheathing
- 3/4 inch tongue and groove plywood or OSB – 11 sheets
Fasteners
- Exterior-rated screws or galvanized framing nails
- Heavy-duty joist hangers strongly recommended
Wall Framing
Framed 16 inch on center.
- 2x4x8 studs
- 120 to 135 total
- Includes perimeter walls
- Additional studs for corners and door framing
- Waste allowance
Plates
- 2x4x18 – 8 (double top plates + bottom plates for four walls)
Double Door Framing
Typical opening: 60 to 72 inches wide.
- 2x12x8 – 2 (header material)
- 1/2 inch plywood spacer
- Jack and king studs included in stud count
Roof Framing
An 18 ft span typically requires 2x10 rafters or larger.
Rafters (4/12 pitch, 16 inch OC)
- 2x10x18 – 28 to 30
- Approximately 14 to 15 rafter pairs
Ridge Board
- 2x12x18 – 1
Collar Ties or Ceiling Joists
- 2x6x18 – 14 to 15
Sheathing
Large wall and roof area significantly increases panel requirements.
Wall Sheathing
- 7/16 inch OSB or plywood – 28 to 30 sheets
- Panel siding may eliminate separate sheathing
Roof Sheathing
- 7/16 inch OSB or plywood – 17 to 18 sheets
Siding
Panel siding is common for large structures.
T1-11 or LP SmartSide Panels
- 28 to 30 sheets
Alternative siding systems require additional trim and backing materials.
Roofing
Underlayment
- 2 to 3 rolls synthetic underlayment
Drip Edge
- 12 to 14 pieces (10 ft lengths)
Shingles
- Approximately 4 squares
- 13 to 16 bundles depending on waste
Roofing Nails
- 12 to 15 lb box
Hardware and Fasteners
- 16d framing nails or structural screws
- 8d nails for sheathing
- Exterior construction screws
- Construction adhesive (8 to 10 tubes)
- Hurricane ties strongly recommended
- Heavy-duty hinges (3 per door)
- Exterior double-door latch or lockset
- Padlock hardware
- Flashing for door header
Estimated Cost Breakdown
Typical 2026 pricing ranges.
- Gravel Base: $450 to $900
- Pressure Treated Floor Framing: $2,300 to $3,600
- Wall Framing Lumber: $1,100 to $1,800
- Roof Framing Lumber: $1,500 to $2,300
- Sheathing (walls and roof): $2,200 to $3,400
- Siding (T1-11): $1,500 to $2,300
- Siding (LP SmartSide): $2,600 to $4,200
- Siding (Vinyl system): $3,300 to $5,400
- Roofing: $950 to $1,500
- Hardware and Fasteners: $500 to $850
Total Estimated Range
With basic panel siding: $8,500 to $10,900
With upgraded siding: $10,900 to $13,500
Costs are driven by:
- Very large floor area (324 sq ft)
- Heavy structural members for wide spans
- Extensive sheathing quantities
- Large roof surface area
- Reinforced door framing
- Increased fastener usage
- Availability of long pressure-treated lumber may significantly affect pricing
If you want exact cut diagrams, printable framing layouts, and step-by-step blueprints for this 18x18 shed, detailed plans eliminate guesswork and reduce lumber waste.
Get the Complete 18x18 Shed Plans Here
Tools Required
Standard framing tools plus equipment suitable for heavy materials.
Essential tools:
- Circular saw
- Miter saw
- Drill and impact driver
- Framing hammer
- 4 ft or longer level
- Speed square
- Tape measure
- Chalk line
- Multiple ladders
- Shovel and rake
- Plate compactor or heavy hand tamper
Helpful tools:
- Framing nailer
- Roofing nailer
- Laser level
- Sawhorses
- Clamps
Assistance is strongly recommended due to the size and weight of components.
Step-by-Step Build Overview
High-level sequence only.
- Prepare and compact gravel base across footprint.
- Build pressure treated floor frame and verify square.
- Install floor sheathing.
- Frame walls on the ground including double door opening.
- Raise walls with assistance, plumb, and brace securely.
- Install double top plates tying walls together.
- Install ridge board and rafters.
- Add collar ties or ceiling joists.
- Install roof sheathing.
- Install drip edge and underlayment.
- Install shingles.
- Install wall sheathing if required.
- Install siding.
- Build and hang double doors.
- Install trim and hardware.
- Verify square frequently to prevent alignment issues.
Common Mistakes
- Using undersized framing for wide spans. Leads to structural sag or bounce.
- Poor base preparation. Causes uneven settling across the structure.
- Attempting to build without assistance. Components are heavy and difficult to handle.
- Losing square during wall assembly. Affects roof alignment and siding installation.
- Underestimating materials. Causes delays and extra costs.
- Weak door framing. Leads to sagging doors over time.
Is It Worth Building Yourself?
DIY material cost: $8,500 to $13,500
Typical prebuilt 18x18 shed delivered in 2026: $16,000 to $28,000
DIY savings typically range from $7,000 to $14,000.
Consider:
- Build time of roughly 7 to 12 days with assistance
- Handling very heavy lumber
- Need for precise layout
- Possible permits and zoning requirements
For homeowners experienced with construction tasks, building yourself is usually financially worthwhile.
Get Exact Cut Diagrams and Printable Plans
This material list provides realistic quantities and cost expectations for an 18x18 shed.
It does not include:
- Exact rafter angle calculations
- Detailed wall framing layouts
- Structural engineering considerations
- Precise overhang measurements
- Optimized cut lists
- Printable construction diagrams
On very large structures, layout errors can waste substantial time and material.
Detailed blueprints with exact measurements, framing layouts, and printable cut sheets simplify construction, reduce waste, and help ensure structural accuracy.
For a large one-time build, complete plans typically save more time and money than they cost by preventing mistakes and rework.