MasterLok-90 (also referred to as ML-90) is a snap together trapezoidal standing seam system designed for projects with slopes as low as 1/4:12.
MasterLok-FS (also referred to as ML-FS) is a mechanically seamed trapezoidal standing seam system designed for projects with slopes as low as 1/4:12. Both panels are best suited for simple sloped roofs without dormers, hips, valleys or other special conditions. ML-90 and ML-FS can be installed over solid decking or substructural members. For seaming tool rental click here. 
MLFS panels are mechanically seamed.  Mechanical seamers and hand crimpers are available for rent through Developmental Industries (DI) at, a website created just for McElroy customers. The rental fees for each type of equipment can be found on this site as well as any additional information you may need to be aware of within the terms and conditions. DI is the only approved supplier for this type of equipment.  

  View an ML-90 installation animation 


  • Factory applied sealant in seam to improve weather-tightness
  • Minimum slope: 1/4:12
  • Can be installed over solid deck or open framing
  • MasterLok-FS is a mechanically seamed profile
  • MasterLok-90 also available with MoistureLok

  • Oil Canning is a natural occurrence in metal panels and is not a cause for panel rejection


Testing Data

  • Fire Rating: Class A
  • Uplift Test: UL580 Class 90,
    ASTM E1592
  • Air Infiltration: ASTM E1680
  • Water Infiltration: ASTM E1646
  • Class 4 Impact Resistance: UL2218
  • Florida State Approval
    1832.2, 1747.1 (ML-90)
  • Florida State Approval 8051.1 (ML-FS)
  • For any available Test Data, Section Properties or Load Tables, please visit our downloads section

Panel Options

  • Panel Width: 24"
  • Coating:
    - Kynar 500® (PVDF)
  • Substrate: 
    - Standard 24 GA Galvalume®
    - Optional 22 GA Galvalume