Selecting & specifying the most appropriate roof system for a project requires solid past experience with several of the available materials and an understanding of roof assembly materials and system options. This article aims to provide design guidance for high-performance industrial roofing sheets. Shared below are the factors to be considered while designing an industrial roof system.
- Load Acting on The Roof: Roofs are constantly under pressure. A roof must be built to endure both upward and downward pressure acting on it. Here are a few weights that industrial roofing sheets are subjected to:
- Dead Load: This includes the weight of the roof structure itself, self-weight of sheeting and purlins, rooftop solar, platforms and walkways along with all the permanently attached materials or structures. Metal roofing sheets in general, are stronger, yet lighter as compared to other roofing options.
- Live Load: People walking or working on the roof contribute to a load of around 75kg/sqm (as per IS 875: Part 2)
- Collateral Load: Any hanging load from purlins
- Wind Uplift Load: Wind uplift load refers to the weight that hits the wall of a building and disperses upwards, creating an uplift force on the roof. This load is resisted by the roof’s downward pushing dead load.
- Effective Roof Slope
- Choosing the Right Roof Profile and Its Thickness
- Effective Purlin Spacing
- Optimized Purlin Section
- CEE Purlins
- ZED Purlins
- ZEE Purlins
- Coating Mass and Paint System of Roof Materials
Roof slope and Roof length play an important role in the selection of profile as well as in gutter design. An increase in the roof slope increases the discharge speed of the water, thereby affecting the gutter and downspout design measurements. A Shallow roof slope and a longer roof length with many numbers of end laps increase the vulnerability of water leakages as the wind will always carry water which will try to penetrate the end laps. In case of a longer roof with lesser crest depth, heavy rains will lead to greater accumulation of water towards eave gutter. This water will try to escape from side laps. If the site is located in a geography where there are high day and night temperature differences, the metal roof will undergo thermal expansion and contraction which will enlarge holes around the screw and lead to leakages. The best bet for shallow roof slope and longer roof will be concealed site roll formed single length panel.
Roof profile sheets constitute a large part of a building surface and contribute to its aesthetics. It serves as a protection to the basic structure from dampness. Choosing the right roof profile includes considering both, the roof slope and the general view of the building. Low-slope roofs require wide-based profiles to allow the rainwater to discharge. Steeper slopes enable to use more patterned profiles. Thickness of the roof profile plays an important role based on the purlin spacing.
Purlins are secondary members mounted on Columns and Rafters. Usually, Roof Purlins support the Roof Sheets, Insulation, Vapour barrier etc. Design of purlins depends upon the Loads on the roof, hanging (collateral) loads under the purlin and Span of the purlin. Some commonly used purlin shapes are ZEE, ZED and CEE purlins which are required for Steel Buildings. Purlin spacing varies basis the roof slopes.
Based on wind pressure, every building structure has 2 zones: end zones & intermediate zones. For both the zones, purlin shape and thickness are designed to match the loads. Tata BlueScope Steel has 3 kinds of Purlins:
The purlin spacing is adjusted based on the calculation of complete wind load in any building.
Roof coatings are designed for adding a protective layer to the roof. It increases the service life of roof assemblies LYSAGHT® range of premium pre painted roofing sheets and wall cladding sheets are manufactured from high-strength steel; COLORBOND® steel and ZINCALUME® steel for longer lifespan. Zn-Al alloy coated steel ensures excellent corrosion resistance that enables longer life under extreme weather conditions, specifically for Industrial buildings, Pre Engineered buildings, infrastructure applications, Light Gauge Steel framing systems and commercial applications Wall cladding and roofing products made from COLORBOND® steel roof sheets are termite and fire-resistant.
Tata BlueScope Steel is one of the leading roofing sheets manufacturers in India. Apart from roofing solutions, the range of products includes Wall Cladding sheets, Decking sheets, Purlins, Solar Module Mounting Structures and allied accessories.