CAN YOUR ROOF HANDLE THE STRESS YOU PUT IT UNDER?
Many people overuse the roof surface on their commercial building, thinking that their roof is stronger than it is. They store things on their roof, allow constant foot traffic, and install equipment that the roof is not structurally capable of supporting. While the roof may hold up for a time, it will sag, it will move, and it will eventually fail.
Many facility managers also underuse their roof. They may have paid extra for an extremely strong roofing system that just sits there untouched for months or years at a time. Rather than utilizing their roof as the facility manager in the first example did, they ignore their roof and leave it alone. While it is always a good idea to avoid putting unnecessary stress on one’s roof, it is also a good idea to properly utilize your roof and take advantage of the features you spend money on when installing it.
If you are in either of the above camps, it is time to reevaluate your roof usage and your roofing system. If you are looking for a new roofing system, consider how you will use it and what type of stress it will be put under. Will it be subject to loads of foot traffic and frequent repair work on equipment? Or will it be mostly left alone? You can partly determine which roofing system is best for your roof based on how you will use your roof.
What is Your Expected Structural Load?
When looking at new roofing systems, it is important to know the expected structural load to be placed on the building. This includes foot traffic, permanent equipment, repair equipment, and natural elements such as rain, snow, and wind. The expected structural load is typically expressed in pounds per square foot, or PSF, and all buildings are designed to handle a certain amount of PSF when they are built.
Expected structural load becomes a problem for building owners when the original roof is replaced or repaired. Each additional piece of material adds to the average PSF on the building, and may eventually become too heavy for the roof system itself or the supports in the building beneath it. For this reason, it is extremely important that each time you make significant repairs or consider a new roofing system, look at your expected structural load, the strength of your current roof and your potential roof, and then eliminate materials that you cannot use.
Which Roofing Materials Are the Strongest?
As you replace your roof, it is important to consider the strength of your building that will hold up the roof. However, certain roofing materials are stronger than others and, while the building may be strong enough to support your expected structural load, your roofing material may not be.
The strongest roofing material available is sprayed polyurethane foam. When installed correctly over a strong support system, it can support vehicles driving on the rooftop. This system adheres directly to the roof surface and creates an extremely strong, rigid foam surface.
Next is concrete, which is a system that is waning in popularity. This roofing material is extremely strong, but is also very heavy and often places more stress on the building beneath it than the load on top of the concrete does. In other words, this material is extremely strong, but it is so heavy it is not always useful.
After concrete comes metal. This is still a very sturdy roofing material depending on the variation chosen, but the material can sag and warp and become creased if exposed to too much weight. While metal is strong, it is also pliable, which means it can crack or bend under pressure.
Built-up roofs are also strong thanks to their many layers, but they fall into the same category as a concrete roof: they are very strong, but are extremely heavy. In a way, their weight cancels out their strength with concern to usefulness.
Finally, almost all other roofing materials are tied for last in terms of strength. Single-ply roofing materials that are typically rolled directly over the existing roof surface add very little strength, and restoration coatings also add no strength. These materials serve more to increase reflectivity and water tightness on the roof than to increase strength.
Sprayed polyurethane foam, or SPF, is the strongest roofing material available when weight is considered. If your building will see heavy traffic and has a high expected structural load, this may very well be your choice. If you have an average to low weight load, you may find yourself anywhere between metal and restoration coatings as your best option. In any case, it is imperative that you consider your expected structural load, the strength of your building, and make your roofing decisions with those factors in mind.