Commercial roofing is not a one-size-fits-all proposition. The “best” roof system design for a facility considers several factors:
- The Existing Building: If there is a roofing system in place, local building codes may not permit another roof to be installed over it, and a tear-off may be required. Or codes may allow an additional roof system to be installed over the current one, depending on the new system’s weight. Also, the roof deck (age, condition, composition, etc.) may dictate how the new roof is installed. If mechanical attachment is used (as opposed to an adhered method) it’s important to choose the correct fasteners for that deck.
- Edge Termination: It’s a critical component of a membrane installation on a flat roof. Termination bars, drip edge, gravel stop, fascia and coping are all used in commercial roof installations and help keep the membrane securely fastened to the perimeter of a building, where wind forces are strongest. Another consideration: if your building is close to the ocean, salt water exposure and high humidity make the corrosion-resistance properties of edge metal very important. Some metal edge products include warranties for installation in salt climates. You might also consider components made from aluminum, copper or zinc, which don’t have the same vulnerability as those made from steel.
- Drainage: The primary job of a roof is to keep contents safe and dry. An installation that protects from the weather is critical, but proper drainage is also important. A new roof design might require upgrades to scuppers, drains, gutters and/or downspouts. If the roof’s flat/low-slope surface doesn’t enable water to flow readily, it might be necessary, for example, to re-pitch the roof using crickets to redirect the water.
- Wind Uplift: Uplift occurs when the air pressure underneath the roof surface is greater than the air pressure above it. Wind blowing across a flat roof causes the air pressure above the roof to decrease, while internal air pressure increases. This causes a net upward force on the roofing system – also known as wind uplift. Uplift factors are more pronounced on taller buildings and those located in designated high wind zones in the United States – primarily geography that’s impacted by hurricanes and tropical storms. Any commercial roof design should consider the uplift situation and require an installation method that will ensure the roof can handle wind conditions. Commercial roof manufacturers’ specifications should have this information.
Contractors, architects, consultants and any other building professionals that are involved in a commercial roofing project should have a thorough understanding of all the factors that can influence the proper design and application of each unique roofing system.