If you own an old commercial building with a flat roof odds are you have an old asphalt roof of some type. These roof surfaces are made up of layers of felt paper and tar stacked up on each other, which over the years it will or it has given you a lot of headaches. They are usually made of felt paper or felt paper that is covered with a layer of gravel, the gravel in theory was to help keep the roof cooler which it does a little but it makes repair much more difficult, not to mention all the additional weight that is added to your roofs stability.
One of the biggest problem with asphalt surfaces is that they dry up and shrink which eventually leads to cracking and this will cause your roof to leak. When this occurs you will notice that the roof surface may look a little like an alligator skin. In order to keep your asphalt roof in good condition it must be maintained. To accomplish this you should have your roof re-coated with an asphalt based coating at least once every five years or so, if you don't it can lead to expensive and time consuming repairs. Over the years your roofs crucial oils are weathered out of the roof surface and it must be restored to maintain integrity, if you have areas with standing water then the process speeds up and your roof will fail in that area most likely first.
If you are on of the unfortunates owners of a gravel roof then you can have even bigger problems. Gravel was put on in a time when it was thought it would be beneficial to help reduce the roofs temperature with cheap gravel, it worked a little but not very much. Gravel roofs undergo the same problems as a regular felt roof but the leaks and standing water areas are much harder to spot. Another huge problem is maintaining the roof, in order to do a maintenance coating all the gravel must be removed. Sounds easier than what it is, you should contract out a gravel suction company to complete this task, but if you are feeling like you need a good workout a few flat shovels and a broom will do the job as well.
Another problem that asphalt roofs face are blistering problems. Blistering occurs when moisture works it way in between the roof layers and expands forming a huge gas pocket, eventually these pockets will expand to a breaking point and crack open, thus leaving you with a hole in your roof. If you have blistering problems you must cut them open with a cross cut so you can fold back the edges and fill them in with roof cement, then fold the cut edges back over the cement thus resealing your roof.
There are a few types of roof coatings that can be used to remedy and repair your roof problems. The most commonly used are asphalt based but if you want a better longer lasting coating you should consider using a elastomeric roof coating, they are much more durable, more energy efficient and longer lasting than asphalt coatings.
Asphalt coatings are generally black or silver in color and have a life span of about five years if applied correctly. They are generally the cheapest of the roof coatings but if you decide to go with this system be sure to purchase ones that are fiberglass embedded, they are much better at stopping and repairing leaks.
Elastomeric coatings are generally white in color and have a life span of 10 to twenty years, there are a few with a 20 year warranty as well, but they are very expensive. Elastomeric roof coatings work very well especially when combined with fiberglass mesh system as its base.