Several important factors come into play in protecting a commercial or strata property investment against the elements. Strategically choosing the type of roofing system used and having a proactive maintenance plan is two very important factors. The performance of a roof has a substantial impact on property operations, tenant & resident satisfaction and property owner costs.
This article contains a summary of the information our property managers share with clients seeking to understand their roofing system and the importance of maintenance. We often share this type of information with clients such as commercial building owners & lease holders through to strata committees & residents of condominiums. Read on to get the information you need to understand flat roof system types and the maintenance that goes with them.
Flat roofs are the most common type of roofing system in use for commercial properties and certain types of strata developments such as low-rise apartments and high-rise condominiums. The most prevalent 5 types of flat roofing systems are:
- Built Up Roofing (also known as BUR)
- Modified Bitumen Roofing
- Ballasted Roofing
- Single Ply Roofing
- Green Roofing Systems
Built Up Roofing (BUR) is also referred to as a tar and gravel roof. It involves a tar infused melt being rolled onto the roof with overlap between layers. Liquid tar is applied to the surface and in between the overlapping layers. Depending on conditions, generally this type of roof lasts 10 to 15 years and then will need additional layers added. A topping material, such as small rock, can be used to protect the roofing system and prolong the useful life of the roof.
Modified Bitumen Roofing is a hybrid of the BUR system where the material is manufactured in a factory and comes in rolls to be applied to the roof deck. The material itself is modified tar or asphalt with rubber typically added for improved performance. Normally a BUR roof underlay is used before the application of the modified bitumen which is applied with adhesive, torch, or hot mopping. A topping material is normally required to protect the roofing system. The lifespan of this type of roof typically exceeds 20 years.
Ballasted Roofing is a membrane roofing system that is normally loose laid on the roof deck and held in place by the weight of a topping such as small rocks or precast concrete pavers. A common material used as such a membrane is EPDM (Ethylene Propylene Diene Monomer). Seams and the membrane are joined with an adhesive. When well maintained, a ballasted roof will typically last over 30 years.
Single Ply Roofing systems simply a single ply sheets of a roofing membrane made from several types of synthetic polymers. During the installation, they are sealed at joints to create waterproofing. While they typically come with a higher price tag, you get what you pay for. Single ply membrane roofs can outlast just about any other roof type, however, it is critical to choose a single ply membrane with a heavy base layer and strong knit design. These membranes are generally excellent in UV and tear resistance; two factors that drive their longevity. In theory, with proper care and maintenance, a single ply membrane roof can last over 50 years. In practice, the better engineered ones were invented about 25 years ago and today the failure & replacement rate can be as low as 1%.
Green Roofing Systems have been used for centuries in Europe to reduce power consumption and manage the heat of city buildings. This trend has been catching in North America in recent years. Green roofs slow roof water drainage down, allowing vegetation to store the water and have water evaporate to the atmosphere directly from the roof. This reduces the burden on both building and city drainage systems tremendously. The basis for a green roofing system is typically the same, mechanically speaking, as a ballasted roof. Instead of the use of loose rock, soil and vegetation are applied. However, the key difference is that the material for the roof also must serve a dual function as a root barrier stopping penetration of roots into the roofing. It is advisable to consider the use of a roofing membrane specifically designed for green roofing. A well designed and installed green roof can last over 20 years.
No article on building materials and technology should end without a mention of maintenance. All roofing needs to have a solid preventative maintenance program in place including the removal of debris and dirt, inspection for damage, as well as the cleaning of downspouts and gutters regularly.
The roof and flashing (the sheet metal which surrounds joins and corners and directions water away from the roof) must have damage or cracking repaired at least annually. The lifespan of the roof should be assessed as part of the maintenance process and a provision for upgrade or replacement should be a part of the budgeting and capital planning process for the property.
In the case of a leak, no matter how small, the source of the leak should be investigated and rectified and the area it appeared (eg ceiling tile or wall) should be restored. Small leaks can easily turn into large leaks in a rainstorm. The importance of restoring ceiling tile or wall is not only aesthetic, it is also important to allow the prompt identification of any further leakage.
In closing, by being informed about your roofing system, its maintenance needs and your future options at upgrade or replacement time, you can ensure you will make better informed decisions about your property investment.