BMT (Bare Metal Thickness)
BMT is the thickness of steel sheet measured without any coating. Used to specify light gauge steel studs, roofing, and cladding in Australian residential construction.
Ask Chalkline about this →BMT stands for Bare Metal Thickness: the thickness of a steel sheet or section measured through the base steel only, excluding any metallic coating (zinc, aluminium-zinc) or paint finish. It is the standard way to specify steel thickness for light gauge steel (LGS) framing, roofing sheet, and cladding in Australian residential construction.
For example, a steel wall stud specified as 0.75mm BMT has 0.75mm of base steel. After hot-dip galvanising, the total thickness including coating will be slightly greater, but the structural and screw-penetration calculations use the BMT figure. Plasterboard screw selection for steel stud work uses BMT to confirm the stud is within the screw’s rated penetration range (typically 0.5mm to 1.2mm BMT for a fine thread needle-point plasterboard screw).
Also known as: base metal thickness (same abbreviation, same meaning).
Category: Steel framing and sheet metal.
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Last updated: 2026-05-10. Verified: 2026-05-10. Quarterly review for currency.