Flat roofing is a practical option for commercial properties. These roofs may be the best choice for large structures and can provide usable space for HVAC or refrigeration equipment. Flat roofs are easier to access than roofing with a steeper slope, which is important because this type of roof requires frequent inspection and maintenance to mitigate or prevent the following problems that may shorten the life of a roof and require commercial roof replacement sooner rather than later.
Flat roofs are not completely level. These designs should usually have a slope of at least a quarter of an inch per foot toward drainage. Any type of flat roof may succumb to ponding as a building shifts or settles or as roofing material becomes worn in particular places. Water can collect in dips or divots. The National Roofing Contractors Association defines ponding as “any water that stays standing on a roof for longer than 48 hours after precipitation.”
Ponding water can wear down any roofing material over time. Standing water also puts a significant amount of extra weight on a roof. A 20-by-20-foot area covered by 1 inch of ponding water can add 2,000 pounds of weight to the roof of a structure, which can increase the risk of a collapse. Standing water is also more likely to result in leaks around open penetrations such as HVAC units, pipes or vents routed through the roofing membrane.
Roofing specialists may be able to make adjustments to promote drainage and prevent ponding. Persistent pooling may require commercial roof replacement with a more effective drainage system. The location of a commercial structure and the condition of the foundation can be important considerations for determining whether a flat or low-slope roof is the best design for a building.
Loose Seams or Flashing
Any roofing material that involves the use of multiple pieces or accommodates roof penetrating structures is prone to develop loose seams. Most single-ply materials such as EPDM and TPO are installed in large sheets to reduce the number of seams. While the seams on TPO roofing are stronger than EPDM seams, neither of these seams are as durable as heat-welded PVC seams, which end up being stronger than the material itself. Regardless of the material, loose seams are a common cause of roof damage that can result in leaks.
Flat roof inspections should always account for the condition of seams. A seam that can be picked apart at the edges with fingers is at risk of causing leaks. Seams may be re-sealed as a temporary fix between commercial roof replacement. It is also important to check the condition of any temporary patches that consist of caulking, roofing tar or specialized single-ply seals. Any gaps or weak points in a flat roof are prone to cause problems.
Many flat roofs rely on flashing to protect the exterior edges of the roof and any open penetrations from damage. As asphalt expands and contracts due to temperature changes, flashing prevents structures from becoming exposed to leaks. Flashing also protects a roof from high winds. Repair or replace loose flashing as soon as possible to prevent leaks and more extensive damage to a flat roof.
Buckling and Cracking
Depending on the material, a flat roof may consist of a single membrane or large pieces of material. As a structure shifts and settles over time, pressure may build up and cause the roof to buckle or crack. These issues may be more common with certain types of roofing materials. Buckling tends to be caused by excessive movement, while cracking can occur due to structural pressure or worn roofing materials. A roof that has buckled requires replacement. Cracking may require repair or replacement depending on the recency and severity of damage.
Commercial Roof Replacement
Over time, asphalt roofing may lose elasticity. As this material cracks and bubbles, it may come to resemble scaly alligator skin. This condition is referred to as alligatoring and indicates the need for roof replacement. Single-ply materials may also develop blisters, cracks, punctures or splits over time. While temporary repairs may be possible, these spots may be more prone to sustaining further damage or developing leaks over time.
Commercial property owners should schedule regular roof maintenance and plan ahead to replace a roof within the recommended time period for the type of material. A conventional built-up roof or modified bitumen can last anywhere from 10 to 20 years. Materials such as EPDM, TPO or spray-on coatings may last as long as 20 years with regular maintenance. A PVC roof can last up to 30 years.
It is important to select the right roof material for a commercial roof replacement. Expert installation and professional maintenance can prevent many of the problems that can occur with flat roofing. Roofing specialists can help property owners choose and care for a roof that lasts for decades.