Trapezoidal roof profile
A trapezoidal roof profile has flat-topped, steep-sided ribs (Trimdek, Klip-Lok). Why it runs lower pitch than corrugated, and how the types differ.
Ask Chalkline about this →A trapezoidal roof profile is a metal roof or wall sheet with flat-topped, steep-sided ribs, forming a trapezoid shape rather than the rounded waves of corrugated (custom orb) sheeting. It is a profile category, not one product: Trimdek, Spandek, and Trimsheet are the common pierce-fix versions, and concealed-fix profiles like Klip-Lok share the same flat-top rib.
What defines it
- Flat-topped ribs. The wide, flat pan between square ribs is what makes it trapezoidal, giving a clean modern line and a stiff sheet.
- Pierce-fix or concealed-fix. Pierce-fix sheets are screwed through the rib crest with a hex-head screw and EPDM washer; concealed-fix sheets clip to the battens with no visible fasteners.
- Low minimum pitch. Trapezoidal runs to lower pitches than corrugated, down to around 2 degrees (1 in 30) for products like Trimdek, because an anti-capillary groove in the side lap stops water wicking uphill. Corrugated needs more fall.
Choosing between them
- Pierce-fix trapezoidal (Trimdek): cheapest and fastest, visible screws, the volume choice.
- Concealed-fix trapezoidal (Klip-Lok): no roof penetrations, best for very low pitch, dearer.
- Corrugated (custom orb): traditional rounded look, needs a steeper pitch.
Profile choice also sets batten spacing and fixings, per the sheet maker and AS 1562.
Also known as: trapezoidal profile, square-rib roofing.
Category: Roofing / metal cladding
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Last updated: 2026-05-26. Verified: 2026-05-26. Quarterly review for currency.