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A simplified guide to the most common roof decking types in America.
Commercial building 'flat roof' decks like those found in the US are the result of centuries of engineering and product design. There are many different types of decks for engineers, architects, and contractors to consider. Each type is distinct in its advantages (and potential disadvantages). DGB Construction, Inc has produced a quick, helpful guide for property owners to familiarize themselves with these various types.
What is a roof deck?
Traditionally forming the very bottom of a roof covering, this layer forms the first true 'covers the entire structure' layer where all other layers above will rest. On larger buildings, the deck will rest on metal 'trusses' that support the weight of the deck and all other layers on top.
Once trusses are in place, installation of the roof deck can begin. Roof decking can be made of wood, cement, metal, or panels made of newer exotic material blends. Each individual type must be approached differently by property owners, architects, engineers, maintenance personnel, and contractors.
Wood Decking - Although now more uncommon for larger commercial buildings, wood decking is historically the most affordable and easiest to build with. Wood is very flammable, so must be treated with special chemicals, coatings, and additional layers to reduce flammability. Wood also cannot bear the heavy loads of rooftop equipment such as air conditioners that concrete or metal roof coverings can.
Cement Decking - Starting in the early 20th century, cement decking overtook wood as the preferred choice of commercial builders. When mixed with iron reinforcement bars (rebar) cement can bear tremendous weight while also resisting warping. Fireproof, but also heavy, it must be cared for to prevent cracking and disintegration. In modern times, lightweight concrete blends are most often used for rooftop decking.
Metal Decking - With the development of the modern steel mill, metal became the go-to for builders looking for a durable, light, and affordable roofing structure. Metal sheets can be manufactured bare with no treatments, or can come in various finishes. Metal sheeting can also be manufactured in several patterns and varying thicknesses at the factory, easing installation greatly.
Synthetic Sheet Decking - Going back to the early 1920s, many manufacturers put forward different synthetic materials able to provide lighter weight, improved durability, and greater waterproof qualities. Through innovation, better and better materials and designs have come to the market. These can be ordered in panels of varying thicknesses and dimensions, depending on what the job requires.
ASTM Deck Manufacturing Standards
Although manufacturers generally attempt to make quality products, past experiences with asbestos, calcium silicate and other hazardous substances have prompted regulatory bodies to form, in order to provide safe professional manufacturing standards. ASTM International is a voluntary organization that tests materials and products on various measures, including walk-on strength, wind resistance, impact resistance, and much more. Roof decking products such as panels will always come with ASTM certification information available.
It is recommended that no matter what type of commercial decking you chose to install, you always verify it has met ASTM standards.
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