Several important factors go into protecting a commercial real estate or condominium investment from the elements. Strategically choosing the type of roofing system used and having a proactive maintenance plan are two very important factors. The performance of a roof has a profound impact on real estate operations, tenant and resident satisfaction, and landlord costs.
This article contains a summary of the information our property managers share with clients looking to understand their roofing system and the importance of maintenance. We often share this type of information with customers such as commercial property owners and leaseholders to condominium boards and condominium residents. Read on to get the information you need to understand the types of flat roof systems and the maintenance that comes with them.
Flat roofs are the most common type of roofing system used for commercial properties and certain types of strata developments such as low-rise apartments and high-rise condominiums. The 5 most common types of flat roof systems are:
- Built Roof (also known as BUR)
- Modified bitumen roof
- Weighted roof
- Single-ply roof
- Green roof systems
Roof built (BUR) is also called tar and gravel roof. It is a tar infused felt rolled over the roof with an overlap between the layers. Liquid tar is applied to the surface and between overlapping layers. Depending on conditions, this type of roof typically lasts 10 to 15 years and will then require additional layers to be added. A roofing material, such as a small rock, can be used to protect the roofing system and extend the useful life of the roof.
Modified bitumen roof is a hybrid of the BUR system where the material is factory made and comes in rolls to be applied to the roof deck. The material itself is tar or modified asphalt with rubber usually added to improve performance. Normally, a BUR roof underlayment is used prior to the application of modified bitumen which is applied with an adhesive, torch or hot mop. Roofing material is normally required to protect the roofing system. The lifespan of this type of roof generally exceeds 20 years.
Weighted roof is a membrane roofing system that is typically laid loose on the roof deck and held in place by the weight of a covering such as small rocks or precast concrete pavers. A material commonly used as a membrane of this type is EPDM (Ethylene Propylene Diene Monomer). The seams and the membrane are joined by an adhesive. When properly maintained, a weighted roof normally lasts over 30 years.
Single-ply roof systems simply single-ply sheets of a roofing membrane made from several types of synthetic polymers. During installation, they are sealed at the joints to create a tightness. Although they usually have a higher price tag, you get what you pay for. Single-ply membrane roofs can last longer than any other type of roof, however, it is essential to choose a single-ply membrane with a heavy base layer and a strong knit design. These membranes are generally excellent in terms of UV and tear resistance; two factors that determine their longevity. In theory, with proper care and maintenance, a single-ply membrane roof can last over 50 years. In practice, the best designed ones were invented around 25 years ago and today the failure and replacement rate can be as low as 1%.
Green roof systems have been used for centuries in Europe to reduce electricity consumption and manage heat in urban buildings. This trend has spread to North America in recent years. Green roofs slow the drainage of water from the roof, allowing vegetation to store water and evaporate water into the atmosphere directly from the roof. This significantly reduces the load on building and city drainage systems. The basis of a green roof system is generally the same, mechanically speaking, as a weighted roof. Instead of using loose rock, soil and vegetation are applied. However, the main difference is that the roof material must also perform a dual function as a root barrier preventing roots from penetrating the roof. It is advisable to consider using a roofing membrane specifically designed for green roofs. A properly designed and installed green roof can last over 20 years.
No article on construction materials and technology should end without mentioning maintenance. All roofs should have a solid preventative maintenance program in place, including removing debris and dirt, inspecting for damage, as well as regularly cleaning downspouts and gutters.
The roof and flashing (the sheet metal that wraps around seams and corners and keeps water away from the roof) should be repaired at least once a year. The life of the roof should be assessed as part of the maintenance process and an allowance for upgrade or replacement should be part of the capital budgeting and planning process for the property.
In the event of a leak, no matter how small, the source of the leak must be found and corrected, and the area where it appeared (eg, ceiling tile or wall) must be restored. Small leaks can easily turn into big leaks during a storm. The importance of restoring a ceiling tile or wall is not only aesthetic, it is also important to allow the rapid identification of any other leaks.
In closing, by being informed about your roofing system, its maintenance needs, and your future options when it comes time to upgrade or replace, you can ensure that you make more informed decisions about your real estate investment.