Substructure material and spacing (Dead load estimate).
Average height from ground to deck surface (affects post weight).
Please enter a valid height.
Total Estimated Deck Weight
2,450 lbs
Total Dead Load (Structure Only)
Deck Area
240 sq ft
Load Per Sq Ft
10.2 psf
Est. Concrete Needed
12 Bags
Weight Breakdown
Detailed Weight Distribution
Component
Unit Weight (Est.)
Total Weight
% of Total
*Formula: Total Weight = (Area × (Decking PSF + Framing PSF)) + Post Weight + Hardware Factor. Hardware is estimated at ~5% of lumber weight.
What is Calculate the Weight of a Deck?
When planning a construction project, the ability to accurately calculate the weight of a deck is a critical engineering step that determines the safety and longevity of the structure. This calculation, often referred to in engineering as the "Dead Load," represents the total weight of the permanent materials that make up the deck itself—including the lumber, decking boards, screws, joist hangers, and railings—before any people or furniture (Live Load) are added.
Homeowners, contractors, and DIY enthusiasts should use this calculation to properly size concrete footings and select appropriate framing members. A common misconception is that a deck only needs to support the people standing on it. In reality, a large wooden deck can weigh several thousand pounds on its own. Failure to account for this massive static weight can lead to foundation settling, structural sagging, or catastrophic collapse.
Calculate the Weight of a Deck: Formula and Math
To calculate the weight of a deck, we use a summation formula that aggregates the weight of individual components based on the deck's total square footage. The standard engineering approach uses Pounds Per Square Foot (PSF) averages for materials.
The Core Formula: Total Dead Load = (Area × (Decking PSF + Framing PSF)) + (Number of Posts × Post Weight) + Hardware Factor
Variable
Meaning
Unit
Typical Range
Area
Total surface area (Length × Width)
sq. ft.
100 – 1,000+
Decking PSF
Weight of surface boards
lbs/ft²
2.0 – 5.0
Framing PSF
Weight of joists, beams, and ledgers
lbs/ft²
4.0 – 8.0
Hardware Factor
Weight of screws, bolts, brackets
%
3% – 5% of wood weight
Note: Pressure treated lumber weight varies significantly by moisture content. "Wet" lumber is much heavier than kiln-dried lumber.
Practical Examples
Example 1: The Standard Suburban Deck
Consider a 20ft x 12ft deck attached to a house. The homeowner chooses standard pressure-treated pine for both the framing and the surface.
Dimensions: 240 sq ft
Materials: 2×8 joists (Framing) and 5/4″ decking.
Calculation:
Decking Load: 240 sq ft × 2.5 psf = 600 lbs
Framing Load: 240 sq ft × 5.0 psf = 1,200 lbs
Posts & Hardware: ~150 lbs
Total Weight: ~1,950 lbs
Interpretation: The footings for this deck must support nearly a ton of permanent weight before a single person steps onto it.
Example 2: The Heavy Duty Composite Deck
A luxury 24ft x 16ft deck using heavy composite decking and dense framing to reduce bounce.
Interpretation: Composite materials often weigh more than wood. This project requires significantly larger concrete piers to distribute the 2+ tons of dead load.
How to Use This Calculator
Follow these steps to accurately calculate the weight of a deck for your specific project:
Measure Dimensions: Enter the total length and width of your deck in feet. If your deck is L-shaped, calculate the two rectangles separately and add them up.
Select Decking Material: Choose the surface material. Composite boards vary in density, while Ipe (tropical hardwood) is extremely heavy.
Select Framing: Choose your joist size. Larger joists (2×10 or 2×12) or tighter spacing (12″ O.C.) increases the wood volume and total weight.
Input Height: Enter the average height from the ground. This estimates the weight of the 4×4 or 6×6 support posts required.
Analyze Results: Use the "Total Estimated Deck Weight" to determine load-bearing requirements for your ledger board and footings.
Key Factors That Affect Deck Weight
When you calculate the weight of a deck, several variables influence the final number. Understanding these can save money on over-engineering or prevent structural failure.
Lumber Moisture Content: Freshly pressure-treated lumber is saturated with chemicals and water. A 2×10 can weigh 50% more when wet than when dry. Engineers usually calculate using the "wet" weight to be safe.
Material Density: Synthetic materials vary. Hollow composite boards are lighter, while solid PVC or capped polymer boards are dense. Tropical hardwoods like Ipe are so dense they sink in water.
Joist Spacing: Reducing joist spacing from 16″ to 12″ on center (often done for composite decks or diagonal decking) adds 25% more framing lumber, significantly increasing the load.
Post Height and Size: A second-story deck requires long 6×6 posts, adding hundreds of pounds of vertical timber compared to a ground-level deck.
Railings and Balusters: While not a primary structural input, heavy glass or wrought iron railings add perimeter weight that must be transferred to the rim joists.
Concrete Footings: While usually considered part of the foundation, if you are calculating the total mass added to the soil, concrete weighs ~150 lbs per cubic foot. A single 12″ x 48″ pier weighs over 500 lbs.
Frequently Asked Questions (FAQ)
Does this calculator include the weight of people (Live Load)?
No. This tool is designed to calculate the weight of a deck structure itself (Dead Load). Building codes typically require decks to support an additional Live Load of 40-50 psf for people and furniture.
Why is knowing the deck weight important for footings?
Footings transfer the load to the soil. If you underestimate the deck's weight, your footings may be too small, causing the deck to sink. You must add the Dead Load (deck weight) + Live Load (people) to size footings correctly.
How heavy is pressure treated lumber?
Southern Yellow Pine, commonly used for framing, weighs approximately 35-50 lbs per cubic foot depending on how wet it is. Our calculator assumes a conservative average for "wet" treated lumber.
Does composite decking weigh more than wood?
Generally, yes. Solid composite boards are denser than cedar or dry pine. However, some "scalloped" or hollow composite boards are engineered to be lighter.
What is the "PSF" listed in the results?
PSF stands for Pounds Per Square Foot. It allows you to compare the "heaviness" of different deck designs regardless of their total size.
Should I include the weight of the concrete footings?
If you are calculating the load on the soil, yes. If you are calculating the load on the posts or ledger board, no.
How does snow load affect the calculation?
Snow load is an environmental load, not part of the deck's dead weight. However, your total structural design must account for Dead Load + Snow Load relative to your local climate zone.
Is a permit required for deck loads?
Yes, almost all jurisdictions require a building permit for decks. Your local inspector will review your load calculations (Dead, Live, and Snow) to ensure safety.