Metal deck load tables are essential tools in selecting the correct decking profile and gauge for your project. They provide engineering data that ensures the deck can safely support the loads required on roofs, floors, or concrete form applications. While these tables may appear technical, understanding how to read them makes it easy to determine whether a deck profile—such as B-Deck—fits your structural needs.
This guide walks you through how to interpret load tables using a real example from our B-Deck (Grade 50 Steel) Load Table.
What Information Do Load Tables Provide?
A typical metal deck load table contains:
- Span lengths (center-to-center spacing of supports)
- Allowable downward/uniform loads (ASD design)
- Gauge (thickness) options
- Deflection-limited service loads (e.g., L/240)
- Shear and web-crippling limits
- Maximum construction and cantilever spans
These values indicate how much load the deck can support at each span length—critical when specifying roofing, flooring, and concrete decking systems.
Key Concepts to Know Before Reading the Table
1. Span
The span is the distance between structural supports such as joists, beams, or purlins. Load tables always assume center-to-center spacing.
2. Dead Load
The dead load is the permanent weight carried by the deck:
- Deck self-weight
- Roofing materials
- Insulation
- Concrete (for form or composite deck)
Dead loads are constant and must always be accounted for.
3. Live Load
The live load is temporary or movable weight:
- Snow
- Equipment during maintenance
- Workers and materials
- Construction loads
Live loads vary and often govern the design.
4. Deflection Limits
Most load tables use a limit such as:
- L/240 for roof applications
- L/360 for ceilings or sensitive finishes
- L/480 for floors
The CSM Metal Deck table includes uniform service loads that cause L/240 deflection, which helps verify usability, not just strength.
How to Read a Metal Deck Load Table (With Real Example)
Let’s walk through a practical example using the CSM B-Deck Grade 50 Steel table, specifically the Allowable Uniform Downward Loads, ASD (PSF) section on page 1.
Step 1: Identify Your Deck Profile
In this example, we are using:
- Profile: B-Deck
- Material: Grade 50 Steel
- Panel width: 36″
- Depth: 1 ½”
Step 2: Choose Your Required Span
Assume your supports are spaced 6′-0″ apart.
We look down the 6′-0″ column in the table.
Step 3: Determine the Deck Gauge (Thickness)
Let’s compare available gauges:
| Gauge | Allowable Load at 6′-0″ Span (Single Span Condition) |
|---|---|
| 22 ga | 94 psf |
| 20 ga | 120 psf |
| 18 ga | 163 psf |
| 16 ga | 210 psf |
(From the “Single Span” row for 6′-0″ on page 1.)
Step 4: Compare Load Requirements
Project Requirements (Example):
- Dead load: 20 psf (roof materials + deck)
- Live load: 40 psf (snow + maintenance)
- Total Required Load: 60 psf
Now compare to the table values:
- 22 ga @ 6′-0″ → 94 psf → Passes
- 20 ga @ 6′-0″ → 120 psf → Passes with margin
- 18 ga @ 6′-0″ → 163 psf → Passes with more margin
- 16 ga @ 6′-0″ → 210 psf → Over-designed for most needs
If your required load is 60 psf, even 22 gauge works safely. If your project includes heavier mechanical units or higher snow loads, you may select 20 ga or thicker for extra capacity.
Step 5: Check Multi-Span Conditions (If Applicable)
Decking installed continuously over three or more supports benefits from multi-span strength.
For example, at 6′-0″ Triple Span, the table shows:
- 22 ga → 124 psf
- 20 ga → 154 psf
- 18 ga → 215 psf
- 16 ga → 270 psf
(From “Triple Span” row for 6′-0″.)
Multi-span conditions increase allowable load, meaning you might be able to use a lighter gauge if the deck runs continuously over multiple supports.
Step 6: Consider Deflection Requirements
On page 2 of the table, CSM Metal Deck provides Uniform Superimposed Service Load that Causes L/240 Deflection.
For a single-span 20-gauge B-Deck at 6′-0″, L/240 load = 55 psf.
If your design requires limiting deflection to L/240 or better, ensure:
Service load ≤ L/240 limit
Otherwise, strength may be acceptable, but deflection may be too high.
Step 7: Check Maximum Construction Loads
CSM Metal Deck includes a table showing allowable construction loads (e.g., weight of workers, tools, wet concrete).
For 20 gauge single-span, the ASD construction span limit is:
- 10′-9″ maximum span
- 2′-9″ cantilever
(from “Maximum Construction and Cantilever Spans,” page 2)
This ensures safe installation before permanent loads are applied.
Full Example Summary
Application: Roof deck
Span: 6′-0″
Required load: 60 psf total
Deflection limit: L/240
Support type: Single-span
Result:
- 22 ga → 94 psf allowable → OK for strength
- L/240 limit = 44 psf → Fails deflection requirement
- 20 ga → L/240 limit at 6’-0” = 55 psf → Marginal
- 18 ga → L/240 limit = 78 psf → Meets deflection + strength
Correct Gauge to Specify:
18 gauge B-Deck for 6′-0″ spans with 60 psf design loads and L/240 deflection limit.
Why This Matters
Choosing the correct deck gauge and span improves:
- Structural safety
- Long-term performance
- Material efficiency
- Installation speed
- Cost optimization
Load tables let you make these decisions confidently and accurately.
CSM Metal Deck Provides Accurate, Code-Compliant Load Data
All CSM load tables—including the B-Deck example used in this guide—are engineered and calculated in accordance with industry standards, including ANSI/SDI RD-2017 and AISI S100-2012 & 2016, ensuring accuracy, safety, and reliable performance in real-world applications. Our tables provide detailed information on section properties, allowable loads, deflection criteria, and construction spans, all designed to support confident decision-making during project planning and specification.
If you need help determining the correct metal deck for your project, our team is here to assist with:
- Span analysis
- Gauge selection
- Deck profile recommendations
- Construction load guidance
- Engineering documentation
Whether you need B-Deck, N-Deck, Form Deck, Composite Deck, or specialty options like vented sheets and hanger tabs, CSM Metal Deck offers high-quality, fast-turnaround products manufactured to meet demanding structural requirements. Contact us today to request a quote, review your project specs, or place an order. We’re ready to supply the decking you need, when you need it.
