Selection of right roofing and walling material for warehouse building is very important and cannot be ignored, as it provides protection to the expensive goods and equipment stored inside the building.
India has witnessed significant strides in the e-commerce business in the last few years. The logistics chains and warehousing facilities across the country are a backbone to support this e-retail and e-commerce revolution. World class retailers derive their efficiencies from their warehousing and logistics capabilities that are very critical to their business. Ensuring your goods remain safe inside the building is the topmost concern for every warehouse owner. Therefore how you build your facility, with the right selection of material is extremely critical.
Selection of right roofing and walling material for warehouse building is very important and cannot be ignored, as it provides protection to the expensive goods/equipment stored inside the building. Any compromise in product quality may lead to paying a high cost on building maintenance or early replacement of the product. This article summarises the key parameters one must consider before procuring the cladding material for your warehouse building.
Roofing and wall cladding is one of the principle building components that provide longevity of the building and protection of goods in rains and extreme weather. Hence it is highly imperative to select the right material that would ensure longer life, low maintenance, greater thermal comfort, high flexibility on design and aesthetics, etc., to your facility. If you are planning on renovation of your exiting building or building a new warehouse; the following checkpoints would help you choose the right cladding material:
Metal cladding is the most preferred material for roof and wall cladding application over other material. When you choose metal cladding, check the following points at the time of drafting the tender specifications or at the time of procurement:
Base metal thickness for the cladding material than total coated thickness:
Structural stability is a function of base metal thickness and steel grade. It is strongly recommended to mention the required BMT. Reputed manufacturer´s produce the base steel material and provide chemical and mechanical test certificates for each coil mentioning the Yield strength of base metal (i.e. minimum 550 MPa or 300 , 340 MPa as per specification). Base Steel determines the strength of the roofing and base steel with varied yield strength is required depending on the roof curve.
Metallic coating type and its mass:
Galvanized (zinc coating) and Zincalume (55%Al-Zn alloy coating) are used in Roof and Wall Cladding application. Zincalume steel is preferred over galvanized steel product and most of buildings use Al-Zn alloy coated steel either in unpainted form or pre-painted form. The corrosion resistance performance depends on its metallic coating mass and not majorly the paint coating. Higher the metallic coating. More the longer corrosion resistance. In 55% Aluminium- Zinc alloy coating should have AZ150 (i.e.. minimum of 150 g/m2 Al-Zn alloy coating total on both side) for the product exposed to exterior application. AZ150 Aluminium- Zinc alloy coating provides up to four times more life than Galvanized (Z275) steel. Other than AZ150, higher coating mass product i.e., AZ200 for 200 gsm on both sides are also available for extreme environmental condition (severe coastal or industrial application).
Luster (Surface treatment) property:
In case of unpainted product, ensure that the manufacture confirms surface finish with anti-darkening property of passivation and separate layer of resin coating. Tata BlueScope Steel confirms the surface finish of Zincalume steel with anti-darkening properties.
Product Compliance to Indian or International Standards:
Ensure that Mill test certificate compliance to international or Indian standard for the product and its environmental category. e. g. COLORBOND XRW & ULTRA steel, AS/NZS 2728, Type 4 for exterior Roof and Wall Cladding application and all properties mentioned as per the industry norms.
Long term aesthetics /Color performance:
Long term aesthetics of buildings depend upon the type of paint system used for manufacturing cladding material. Paint comprises three main ingredients: Resin, Pigment and Solvents. The pigments´ purpose is to provide colour and hiding ability to finishes and resin forms the desired film and binds the coating to the substrate, providing the weather-resistance and durability properties desirable in an architectural coating. Ensure that the manufacturer uses stable super durable polyester resin system with stable inorganic pigments than organic pigments. Inorganics pigments have superior colour stability and chemical resistance but are expensive than the organic pigments. Lead pigments are carcinogenic hence not recommended in any paint system. COLORBOND- Pre-painted Zincalume steel is tested and proven product and it´s been taken care of all parameters, offers long term durability and aesthetics to your building.
Thermal reflectivity of cladding material:
Average temperature around the world has increased over the last few years. The frequency of hot days and nights have increased and is likely to continue to be so. It is creating stressful, unhealthy, and unproductive working conditions. These conditions are more common in cities, where urban heat islands (UHIs) are caused by the intensity of non-reflective, high mass materials that absorb a comparatively large proportion of solar radiation. There is a need for alternatives to mechanical air-cooling solutions to reduce energy demand & related greenhouse gas emissions.
Thermatech technology is a solar reflectance technology incorporated into COLORBOND steel without changing its appearance. It lowers surface temperature by absorbing lesser heat from the sun. In other words, COLORBOND® steel with ThermatechTM technology is able to reflect more solar heat, thereby keeping both roofs and buildings cooler. Reduced heat stress also means greater durability for entire roofing systems and superior ROI. Thus, Thermatech™ solar reflectance technology ensures cool comfort, while reducing energy cost. Thermal reflectivity of painted products varies from colour to colour, very dark and bright colours fade fast and have more heat radiated inside the building. Tata BlueScope has developed some colours of COLORBOND steel are complying the LEED (Leadership in Energy and Environmental Design - SRI value > 78 in low slope and SRI value >29 in steep slope building) credits. Always go with standard earthy colours to keep building newer for longer. Please ensure that the cladding material should have higher Solar Reflectance Index (SRI) values and if you are going for green certification, the SRI value should meet LEED.
Most of the buildings use bare / unpainted product on roofs, as it is not visible from the ground and have some cost benefit initially. Since Tata BlueScope Colorbond steel has THERMATECH™ solar reflectance technology, we suggest you to use COLORBOND® steel as a roofing material in any form of profile. It can reduce the temperature inside the building by up to 6C in hot weather (depending upon the level of insulation already installed), thus reducing the need for air conditioning. In moderate to hot climates, it can reduce annual cooling energy consumption by up to 15% compared to roofing materials of similar colour with low solar reflectance. (The average reduction is about 5%: results will differ depending on the level of insulation, building shape and function).
The technology helps mitigate the Urban Heat Island (UHI) effect.
Roof and wall cladding profile shape/design:
In the market various types of profile shapes are available and selection of the right one is critical. It is imperative to check the profile shape and its design criteria on serviceability and strength.
It is advised to always go for a reputed manufacturer who can provide profile wind pressure table data and also provide technical /detailing support.
Fastener for fixing the roofing sheet or clips:
The performance of fasteners used, must have the same or superior service life as the roof and wall cladding material and shall comply with Australian Standard AS 566 class 3 or class 4. The washers containing significant levels of conductive carbon black fillers are not suitable for use with our products.
In continuation of product selection, the design and structural details of a building are critical to its expected service life. A better understanding of design issues including roof slope, sheet laps, crevices, fastening techniques and the areas conducive to the build-up of dirt / contaminations, are to be addressed appropriately. The areas with build-up of dirt/contaminations need cleaning at regular intervals. It is to be noted that the components must be free of any ponding issue and there are least numbers of crevices. It is because accumulation of water at these locations for long periods is not good for coated steel components.
Different environments affect the life of coated steel differently. Therefore, selection of coated steel material would require an understanding of the external and internal environment to which it is going to be subjected to. Particular attention must be paid to coastal, aggressive industrial situations and intensive farming applications. To get maximum life, the important factor is selection of the appropriate coated steel at the specification stage of the building. The new Indian standards will facilitate more uses of high corrosion resistant coated steel in buildings, with a view to provide long life and aesthetic durability.
(Authored by Mahendra Pingle, Dy. General Manager - Market Development, Tata BlueScope Steel Limited)