Commercial (Flat) Roofing

Commercial (Flat) Roofing2021-05-15T21:58:57+06:00

Flat Roof Installation & Repair

If you are looking for a commercial roofing company for flat roof installation or repair call Swift Construction, a division of CEI Electrical & Mechanical, for a free estimate.  We have a dedicated team that focus solely on flat roof installation and repair with over 20 years of experience.

Commercial buildings typically have roofs that are nearly level compared to the sloped roofs that are characteristic of residential buildings in the United States. These roofs are classified as “flat,” although they may actually have a pitch of up to 10 degrees to allow for drainage. In comparison, the sloped roof of a residence typically has a pitch of at least 35 degrees. Flat roofs are often used as a living or storage space, which isn’t possible with sloped roofs. These differences mean that commercial roofs have distinct requirements for their installation, maintenance and repair.

Industrial Flat Roof Installation Repair


Rain water naturally runs down a sloped roof without any additional features, but drainage is a primary consideration during the installation of a flat roof. These roofs are usually built with a slight incline so rain water can run into a gutter system, although exceptions exist.

A small building such as a garden shed may have a simple roof made of a single metal sheet that allows water to run freely off the edge. However, a gutter system is still useful for keeping the walls and foundation of these buildings dry. The gutters on a small building typically lead rain water to the ground or a specially designed area known as a soakaway. The roofs of larger commercial buildings usually have a gutter system that leads water to the drainage system that’s essential for any built-up area. Some flat roofs are specifically designed to allow water to accumulate in a pool, usually for the purpose of storing rain water or aesthetic purposes.

Roofs must be covered with some type of waterproof material to prevent water from soaking through it. Flat roofs in the United States are typically covered in roofing felt, which is a fibrous material impregnated with asphalt or tar. Felt also has an outer covering of gravel to provide additional protection from heat and other weather effects.

The decking for commercial roofs can be made of a variety of materials, which generally include some type of concrete, steel or wood. Oriented strand board (OSB) is the most common wood material for commercial roof decking, although plywood and chipboard are also used. Wood decking requires at least two coats of asphalt applied as a hot liquid, with three or four coats being more common.

Flat Roof Installation on Industrial hall

Flat roof with skylight and hydro insulation membranes


Commercial roof maintenance generally requires more work than sloped roofs. The greatest threat to flat roofs is usually the possibility of pooling water, which can eventually penetrate the roof’s membrane. People and weather events can also remove the gravel covering the membrane, exposing it to the sun. This can cause the membrane to blister and crack, allowing water to get through. The life expectancy of a roof depends on the quality of its materials, construction and maintenance, with 20 to 30 years being the average for roofs made of felt, tar and gravel.

The best practices for flat roof maintenance include getting rid of standing water quickly, typically within 48 hours. Pooling can be especially damaging in colder climates, where water can get between materials and weaken seams by repeatedly freezing and thawing. Maintenance personnel can remove water at the edge of a roof by installing drains or scuppers, but water in the center of the roof requires a siphon. An automatic siphon consists of a hose, wet/dry vacuum, check valve and timer. Operators can set the timer to start the siphon several times each day to remove accumulated water.

Flat roofs should also be inspected at least twice each year and after every major storm. Flashings require particular attention, as a space between the flashing and membrane accounts for about 90 percent of roof leaks. Maintenance workers typically fill these spaces with a combination of mesh and plastic cement, using a trowel to make a smooth surface. Clearing debris from roof drains is another important maintenance task, since clogs lead to increased pooling.


A leak that remains undiscovered for a long period is one of the most common causes of major damage to a flat roof. This process allows water to penetrate the decking and reach other materials that are easily damaged by water, especially insulation. Long-term rot can weaken the entire roof structure and pose a health threat when mold releases spores into the air. Furthermore, wet insulation has virtually no ability to actually insulate anything, which increases heating and cooling costs.

The initial goal in assessing major damage to a roof is to determine whether a flat roof repair will be more cost effective than replacing the roof. This decision primarily depends on the extent of the damage, although the nature and location of the damage may also be important factors. Business owners must also consider the loss of revenue that will occur that will occur if the entire roof is replaced. Damage that’s restricted to a particular area is more likely to be repairable, especially if the roof is still structurally sound. For example, it may be possible to repair even a major leak in an asphalt roof with multiple torch-down patches.

The general rule is that the roof should be replaced if at least one-fourth of it requires repair. However, other factors may make replacement the recommended course of action for a roof with less than one-fourth damage. The most common reason for this scenario is insulation that isn’t performing well because it remains wet. A previous commercial roof repair that hasn’t held up is also an indication that replacement will be more practical than repair.

Flat roof with ventilation & skylight on industrial building


CEI Swift Construction has been serving Kansas City and surrounding areas out to 100 miles since 1985. Our primary business was initially sign maintenance, but we’ve since expanded our services to meet other needs of our customers. We currently perform a variety of commercial construction projects, including roof repair and replacement. Contact us today to learn more about how we can help your business.