Steel framing
Steel Gauge vs. Mils: Specify Framing Thickness Clearly
Understand gauge, mils, minimum base-metal thickness, and design thickness so steel framing quotes and submittals describe the same intended product.
Why a gauge-only description creates confusion
Gauge is familiar jobsite shorthand, but it is not a complete description of a cold-formed framing member. A mil is one thousandth of an inch. Published framing data distinguish thickness designation, minimum base-steel thickness, and design thickness; those terms should not be collapsed into a single number.
BuildSteel's ordering reference lists different thickness entries under drywall and structural versions of a gauge label. This is why repeating a gauge number from a phone conversation is less reliable than attaching the complete approved designation and product sheet.
References: How to order cold-formed steel framing
Keep thickness terms in their own columns
The useful comparison is between the same fields on the requested and offered products. Do not compare the design-thickness entry for one product with the minimum-thickness entry for another and conclude that one is undersized.
| Term | What to record | What to avoid |
|---|---|---|
| Gauge | Any reference label used by the supplier | Using it as the only requirement |
| Thickness designation | The designation shown in the product data | Assuming every printed number is a measured thickness |
| Minimum base-steel thickness | Published minimum excluding coating | Comparing it with coated outside measurements |
| Design thickness | Value used in the stated engineering data | Treating it as a different product without checking context |
Read the marking and the document together
Manufacturer identification information connects product markings to the member family, thickness, and other material attributes. ClarkDietrich provides a product-identification reference for this purpose. Use the current reference for the supplied manufacturer rather than assuming all markings follow an identical visual format.
On receipt, photograph the marking clearly enough to read and associate it with the bundle number. If a marking is incomplete or difficult to interpret, request written identification from the supplier before distributing the material across different wall locations.
References: Product identification and thickness designations
Account for performance-based products
Some nonstructural products are offered as equivalent-performance or EQ framing. Their declared performance must be evaluated using the appropriate product data and assembly conditions. A familiar gauge comparison is not enough to establish that an alternate fits the intended wall.
The practical purchasing step is to ask which document demonstrates the requested performance and which assumptions it uses. Keep wall height, board arrangement, movement details, and attachments connected to that review. An alternate can only be evaluated against a clearly stated requirement.
References: Specifying Cold-Formed Steel Framing · Performance-Based Decision Guide PB101-23
Example: two quotes with the same gauge label
Suppose two quotations both describe a wall stud using the same gauge, but one includes a full standard designation and the other lists a proprietary product name. Do not silently combine the quantities. Request the base-metal thickness, grade, profile, coating, and supporting performance information for each.
Create a comparison row for every differing field. If the project accepts a performance-based alternate, record that acceptance against the wall types it actually covers. This prevents a decision made for an ordinary partition from spreading to an exterior or otherwise different wall.
- Copy the specified designation without shortening it.
- Request the manufacturer's current product sheet.
- Compare minimum with minimum and design with design.
- Keep coating and steel grade visible as separate properties.
- Record the reviewed locations for any accepted alternate.
Use precise language in a component list
A useful line item states the profile designation, length, quantity, grade and coating where specified, plus the document reference. Gauge can remain as a secondary label for convenience. That gives estimating, purchasing, receiving, and installation teams the same reference point.
If the drawing and specification disagree, record the conflict rather than selecting whichever entry seems heavier. Resolving one concise question early is better than receiving two different products under the same informal name.
Common questions
Does mil mean millimeter?
No. In steel-thickness terminology, one mil is one thousandth of an inch. Millimeters are a different unit; label units explicitly in comparisons.
Is thicker always an acceptable substitution?
No. A thickness change can affect fit, connections, installation, and the evaluated assembly. Submit the proposed member and supporting details for the required project review.
Sources & further reading
Use the current documentation for the exact product and project. Source links do not imply a partnership or endorsement.
- How to order cold-formed steel framing SFIA / BuildSteel
- Product identification and thickness designations ClarkDietrich
- Specifying Cold-Formed Steel Framing SFIA / BuildSteel
- Performance-Based Decision Guide PB101-23 Steel Framing Industry Association
Prepared with AI assistance. Linked references require current project-specific review. How these guides are prepared.
Products related to this guide
Explore the catalog references and compare the published options with your project documents. Products sharing a guide are not necessarily interchangeable.
Prepare a supply inquiry
- Record the project drawing or detail and the specified product, profile, or system.
- List the complete configuration, physical units, quantities, and cuts per piece.
- Request current manufacturer documents; confirm compatibility, price, and availability before ordering.
- Obtain the responsible professional's review for loads, code requirements, or installation.