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Curving
last updated 16/11/12

This article aims to give an overview of the processes and provides a sample of the information available from SteelSelect to help you in your design process.

Overview

When considering curved sheeting for your design you have two significantly different options to choose from:

Spring Curving Pre-curved Sheeting

At a glance, the difference
Pre-curved* sheeting uses G300 tensile strength material which is commonly referred to as 'soft feed'. The material is profiled into a corrugated shape and is then curved to the radii in a curving machine. Many people refer to LYSAGHT CUSTOM BLUE ORB® when specifying this product. Other manufacturers do produce their own pre-curved sheeting in the identical manner; Stramit Building Products refer to their product as Stramit® Curving Quality and Metroll refer to their product as Corodek Curving Quality and Fielders Steel Roofing refer to their product as Curving Quality Corrugated. Pre-curved sheets are commonly used on verandahs, and designs where a tight radii is required that can not be achieved by spring curving. When designing projects with long length pre-curved sheeting you need to consider transportation. The minimum radii varies slightly because of individual machine tolerances, as a guide, work between a 300-400mm radius (allow a straight section at the end of the radii of 50-100mm).

Spring Curving uses the same grade material as standard roofing material (G550 tensile strength, G300 'soft feed' can also be spring curved but is not typical due its higher price compared to standard high tensile lighter gauges) and is supplied onsite as straight sheets. The sheets are then installed over the curved roof frame to a radius acceptable to the rollform manufacturers' recommendations. Spring Curving is common on gentle sloping roofs that do not require a tight radius.

Available gauges
Because pre-curved* sheeting is manufactured from G300 'soft feed', a thicker base material is required to achieve a reasonable span between purlins. COLORBOND® steel, ZINCALUME® steel & COLORBOND® Ultra steel are available in 0.60 BMT**, COLORBOND® stainless steel & COLORBOND® Metallic steel are available in 0.55 BMT.

Spring Curving as detailed above, uses standard G550 roofing material and is available in the standard gauges; 0.42 BMT, 0.48 BMT & 0.60 BMT (subject to supplier availability).

Costing
Due to the heavier gauge of pre-curved roofing and the additional process of factory curving the sheets to the radii, pre-curved sheeting has a higher m2 cost than standard roofing that is spring curved (Please contact the supplier direct for an exact costing). Both styles of curved roofing typically require more time to install than straight sheeting.

*Crank Curving is the process of curving sheets by placing a series of breaks in the profile to create a radius, G550 material can be curved using this process. This process is not available from all suppliers.

**BMT denotes - Base Metal Thickness

Design Resources

Commonly Asked Questions

Question
Is it possible to join G300 corrugated pre-curved sheets with standard G550 corrugated straight sheeting?

Answer
Yes, but it is critical that the sheet profile matches and the sheeting is installed in the correct laying procedure. It is best to consult the rollform manufacturer to discuss the lapping of sheets.

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