This document discusses sheet steel gauges, thicknesses, and terminology used within the construction industry. It defines key terms like nominal thickness, minimum thickness, gauge number, and design thickness. Tables are provided showing the relationships between gauge numbers, design thicknesses, and minimum base steel thicknesses according to industry standards. Additional information is given on metallic coatings and their minimum thicknesses, as well as standard thickness equivalents used for steel studs. The goal is to explain why sheet steel products should be specified according to their decimal thickness instead of gauge number to avoid confusion.
This document discusses sheet steel gauges, thicknesses, and terminology used within the construction industry. It defines key terms like nominal thickness, minimum thickness, gauge number, and design thickness. Tables are provided showing the relationships between gauge numbers, design thicknesses, and minimum base steel thicknesses according to industry standards. Additional information is given on metallic coatings and their minimum thicknesses, as well as standard thickness equivalents used for steel studs. The goal is to explain why sheet steel products should be specified according to their decimal thickness instead of gauge number to avoid confusion.
This document discusses sheet steel gauges, thicknesses, and terminology used within the construction industry. It defines key terms like nominal thickness, minimum thickness, gauge number, and design thickness. Tables are provided showing the relationships between gauge numbers, design thicknesses, and minimum base steel thicknesses according to industry standards. Additional information is given on metallic coatings and their minimum thicknesses, as well as standard thickness equivalents used for steel studs. The goal is to explain why sheet steel products should be specified according to their decimal thickness instead of gauge number to avoid confusion.
This document discusses sheet steel gauges, thicknesses, and terminology used within the construction industry. It defines key terms like nominal thickness, minimum thickness, gauge number, and design thickness. Tables are provided showing the relationships between gauge numbers, design thicknesses, and minimum base steel thicknesses according to industry standards. Additional information is given on metallic coatings and their minimum thicknesses, as well as standard thickness equivalents used for steel studs. The goal is to explain why sheet steel products should be specified according to their decimal thickness instead of gauge number to avoid confusion.
C a n a d i a n S h e e t S t e e l B u i l d i n g I n s t i t u t e
Sheet Steel Facts
May 2006 Sheet Steel Gauges and Thicknesses Within the construction industry there is often confusion Base Steel Thickness: The thickness of the sheet steel material over gauges, gauge numbers and the actual thickness. The without any coatings. industry has been trying to move away from gauge numbers, without complete success. The following information will Coated Thickness: The thickness of the steel sheet including show why sheet steel products should be specified to the any metallic coatings (i.e. zinc or 55% aluminum-zinc alloy) decimal thickness. and paint coatings.
Design Thickness: The design thickness is the thickness of
Manufacturers’ Standard Gauge For the base steel only, and is used by the engineer to determine Steel Sheets the structural properties of the cold formed product. This is The most common gauge system used in Canada for the thickness that a manufacturer will list in their product structural sheet steel products is the Manufacturers’ catalogues and load tables, where it could also be called the Standard Gauge (MSG). The MSG for steel sheets was nominal base steel thickness. developed having a DEFINITE THICKNESS equivalent for each gauge number. In the standard gauge system the Minimum Thickness: The minimum thickness of structural density of steel is taken as 489.6 lbs/ft3, or 40.80 lbs/ft2/in. sheet steel building products delivered to the job site will be However, since sheet weights are calculated on the basis of the design thickness minus the maximum allowable under- specified width and length, with all shearing on the over tolerance specified by the CSA-S136-2001 Standard or the side, and also since sheets are somewhat thicker at the centre material specification, whichever is the more restrictive. The than they are at the edges, a further adjustment was made minimum thickness allowed by the CSA-S136-2001 Standard to obtain a closer approximation for inter-changeability is 95% of the design thickness. between weight and thickness. Over a long period of time this value for sheets has been found to be close to 2.5 per Gauge Number And Decimal Thickness cent heavier than 40.80 lb/ft2/in. A figure of 41.820 lb/ft2/in Table 1 shows the relationship between the MSG numbers, is the one commonly used to express the relationship the nominal or design thickness, and the minimum between weight and thickness for steel sheet. thickness based on the CSA-S136-2001 Standard. Table 1 - MSG Sheet Steel Gauge The Galvanized Sheet Gauge Numbers and Thickness The Galvanized Sheet Gauge is an older system used primarily by the trades consuming non-structural galvanized Gauge Minimum Base Steel Design Thickness steel and is a measure of the zinc coated sheet thickness. It Number Thickness (Nominal Base was developed in the early days of galvanizing before (95% of Design Thickness) Steel Thickness) sophisticated wipers were available and, consequently, zinc inches mm inches mm thicknesses were thicker than today. The GSG system was 8 0.1562 3.967 0.1644 4.176 used on some of the older gauge charts published years ago 10 0.1278 3.245 0.1345 3.416 that unfortunately still seem to get used even today. 12 0.0994 2.524 0.1046 2.657 13 0.0852 2.164 0.0897 2.278 Thickness Definitions 14 0.0710 1.802 0.0747 1.897 There are a number of terms used for sheet steel products 15 0.0639 1.624 0.0673 1.709 that need to be explained because they will affect the 16 0.0568 1.443 0.0598 1.519 thickness of product that could be delivered to the job site. 18 0.0454 1.153 0.0478 1.214 20 0.0341 0.866 0.0359 0.912 Nominal Thickness: When sheet steel is produced by the 22 0.0284 0.721 0.0299 0.759 steel companies it is manufactured to a target or “nominal” 24 0.0227 0.577 0.0239 0.607 thickness. As with all manufacturing processes, variations in 26 0.0170 0.432 0.0179 0.455 the final thickness of the sheet are unavoidable. However, 28 0.0142 0.359 0.0149 0.378 the thickness is controlled very tightly to ensure that it does 29 0.0128 0.326 0.0135 0.343 not fall below the minimum thickness (as described below). 30 0.0114 0.290 0.0120 0.305
(Replaces February 2006)
C a n a d i a n S h e e t S t e e l B u i l d i n g I n s t i t u t e
Minimum Thickness Allowance Table 4 – Minimum Thickness for
for Coatings Prefinished(1) Sheet Sheet steel products are normally coated with a metallic coating (i.e. zinc or 55% aluminum-zinc alloy), and also may Minimum Base Steel be painted. The minimum thicknesses of typical hot-dipped Gauge Thickness Minimum Coated metallic coatings are given in Table 2. The metallic coating Number (95% of Design Thickness) Steel Thickness thickness must be added to the minimum base sheet inches mm inches mm thickness when determining the delivered sheet thickness. 20 0.0341 0.866 0.0369 0.939 Metallic coatings are also subject to manufacturing 22 0.0284 0.721 0.0312 0.794 tolerances the same as the base steel. Therefore, the actual 24 0.0227 0.577 0.0255 0.650 thickness of the metallic coating will generally be greater 26 0.0170 0.432 0.0198 0.505 than the minimums listed in Table 2. This factor needs to 28 0.0142 0.359 0.0170 0.432 be considered when attempting to verify the base steel 29 0.0128 0.326 0.0156 0.399 thickness of a coated product. 30 0.0114 0.290 0.0142 0.363 (1) The sheet has a G90 (Z275) zinc coating (0.0015 in./0.040 mm), an Table 2 - Minimum Metallic Coating 8000+ Series paint coating on the finish side (0.001 in./0.025 mm) and a Thicknesses wash coat on the reverse side (0.0003 in./0.008 mm).
Minimum Minimum Additional Gauge Equivalents for
Coating Thickness Coating Thickness Designation (inches) Designation (mm) Steel Studs The steel stud industry in Canada has in regular use additional A01 0.0004 ZF001 0.010 gauge number equivalents that are different than shown in Table 1. A25 0.0007 ZF075 0.018 Starting in June 2004, Canada will join the United States and adopt G01 0.0004 Z001 0.010 a common set of standard base steel thicknesses for lightweight G60 0.0010 Z180 0.025 steel framing components (e.g. studs and joists). These gauges are G90 0.0015 Z275 0.038 unique to this industry and are shown in Table 5. The CSA-S136- AZ50 0.0016 AZM150 0.041 2001 maximum under-tolerance also applies to these gauges as well AZ55 0.0018 AZM165 0.046 as does the metallic coating allowances listed in Table 2. AZ60 0.0020 AZM180 0.051 Table 5 – Standard Thicknesses for Lightweight Steel Framing Components A significant amount of sheet steel is also prefinished with a paint system on top of the metallic coating. The thickness Designation Minimum Base Design Steel Framing of these paint/primer layers must also be included when Thickness Steel Thickness(1) Thickness Gauge No. (for (mils)(2) (in.) (mm) (in.) (mm) reference only) measuring the thickness of the sheet. The thicknesses of typical paint coatings vary from 0.0003 to 0.001 in. (0.008 18 0.0179 0.455 0.0188 0.478 25 to 0.025 mm) per side. Some thick film paint systems (e.g. 30 0.0296 0.752 0.0312 0.792 20 – Drywall Barrier Series) have thicknesses of 0.004 to 0.012 in. (0.100 33 0.0329 0.836 0.0346 0.879 20 – Structural to 0.300 mm). Listed in Table 3 are the thicknesses of 43 0.0428 1.087 0.0451 1.146 18 common prefinished paint systems used in Canada. 54 0.0538 1.367 0.0566 1.438 16 68 0.0677 1.720 0.0713 1.811 14 Table 3 - Thicknesses of Prefinished 97 0.0966 2.454 0.1017 2.583 12 Paint Systems 118 0.1180 2.997 0.1242 3.155 10 Paint Nominal Thickness(1) (1) Minimum thickness represents 95% of the design thickness. Metric (mm) minimum thicknesses were calculated by converting the Imperial (in.) values. System mm (2) A “mil” is 1/1000 of an inch (e.g. 30 mils is 0.030 inches). inches 8000+ Series, HMP 0.001 0.025 Conclusion 10000 Series 0.001 0.025 An important thing to remember about gauge numbers is that Elite and Metallic Series 0.002 0.051 they do not refer to only one thickness but instead represent a Barrier Series – 4 mil 0.004 0.100 range of thicknesses within the allowable tolerances, or to Barrier Series – 8 mil 0.008 0.200 different thicknesses for different products. Gauge numbers are Barrier Series – 12 mil 0.012 0.300 not regulated and are generally used for convenience in sales Washcoat 0.0003 0.008 literature. Decimal thickness is required for structural design (1) The paint thicknesses listed are per coated side. and material ordering. The steel industry encourages everyone to use decimal thicknesses in specifying sheet steel products and avoid the potential problems inherent with gauges. Minimum Thickness for Common Prefinished Material For More Information Table 4 shows the minimum thickness for a galvanized sheet For more information on sheet steel building products, or with a common paint system. to order any CSSBI publications, contact the CSSBI at the address shown below or visit the web site at www.cssbi.ca 652 Bishop St. N., Unit 2A, Cambridge, Ontario N3H 4V6 • Tel.: (519) 650-1285 • Fax: (519) 650-8081