Flat Roof Systems: More Than Meets the Eye

To continue my post from last week I’m going to go over how the three most common flat roof systems are installed to help you understand how they leak and why leaks can be so difficult to find.

The first thing to keep in mind when discussing roof leaks with any type of roofing system is that water is sneaky stuff; it always follows the path of least resistance. Gravity pulls water along until it finds even the smallest hole to drop through, then it will flow further along, searching for yet another opening and on…and on….and on. As it moves along it will soak anything in its way: wood decking, insulation, drywall or ceiling tiles and facilitating the growth of hazardous mold. Eventually you see it as water stained drywall or a puddle on the floor.

Knowing how your roof system works can be a very big advantage when trying to decide the best course of action to deal with water leaks.

All roof systems start with a roof decking; this decking is most commonly a wood product like plywood or oriented strand board (OSB). The roof deck is a structural element and serves as the base for any roof system.

1) Built Up Roofing. Built up roofing (BUR) is the single most common roof system used in commercial and industrial buildings. It is comprised of layers of felt paper or a reinforcing fibrous material which is then covered by hot tar or asphalt. This process is repeated with each layer comprising piles of waterproof protection. After the final pile is completed, it is covered with an aggregate usually gravel. BRU systems generally have a long life, but when they do break down they are very difficult to inspect from above.

2) Single ply Roofing. Single ply roofing consists of a rubber-like membrane (rubber, thermoplastic or PVC) laid over a later of insulating board. The insulating board usually comes in 4’ by 8’ or 4' by 12’ sections with a water proof tape applied to the seams between boards. The roofing membrane can be adhered to the insulation board by different means depending on the product used. It can be heated and essentially melted to the substrate, fully glued or glued around the perimeter the weighted with stone to hold it in place. Seams in the roofing membrane are either heat sealed or chemically sealed with glue.

3) Modified Bitumen Roofing. MB roofing is also a layer system consisting of reinforcing fabrics covered with a rolled asphalt material. These materials can be adhered with hot asphalt that is mopped on, fully glued on, or some products come with a pre-applied adhesive backing. As with the single ply systems, the seams are either heat sealed or glued. All of these systems can work extremely well but they all have some of the same weaknesses - seams that can fail and mechanical penetration that can break down.

In my next post I will explain why leaks in these roof systems can be so difficult to locate and how Infrared Scanning can be an invaluable tool in your maintenance tool box. Interested in learning more? Call me at 803-328-2889 and let’s talk!

IR Infrared Services provides top quality thermographic service at a competitive price to commercial users in North Carolina and South Carolina. For more information, visit us on the web or follow us on Twitter: www.twitter.com/infraredscans. We are proud to offer the very best thermography services in North Carolina and South Carolina!