Built up or modified BIT roofs have increased in popularity for several reasons. A single ply is elastic and durable. No gravel surfacing or coatings are required making them less costly to install and maintain. Inspections are relatively easy and leaks are easier to find and repair than with many other kinds of roofing materials. Those are the benefits typically outlined by marketers and they are true for the most part as long as you do some preventative maintenance.
In truth, some of the materials that are covered with granules on the surface may need to be recoated after a few years due to loss of the granules. Regular inspections will reveal this problem.
Unless the roofing is new, it is a good idea to find out how long ago the material was put in place and to learn about the type of material that was used. Some materials last longer than others. The inexpensive single layer asphalt-impregnated materials have a relatively short lifespan of less than 15 years. Other materials can last as long as 20 years if the weather in the area is not too severe.
Once you find out how long ago the BIT roof was put in and you learn about the materials that were used, you can plan for regular inspections. You can do the inspection yourself or let your roof maintenance crew handle it. Flat and low slope roofs should be inspected twice a year. Steeply sloping roofs should be inspected yearly but the drainage system should be inspected at least twice a year.
In most areas, inspections should be done in the spring after the harsh winter weather is over to assess any damage done by melting ice or heavy snow. The second inspection should be conducted during the fall to reduce the risk of snow damage or winter leaks.
In addition to assessing granule loss, there are several things to look for. Cracks and gaps between the sheets can eventually lead to leaks. It saves money to repair the cracks and close the gaps before a leak occurs. Crazing is a precursor to cracking. It might not be necessary to do a roof repair until the next inspection but it is a good idea to plan to make a repair as soon as possible.
Preventative maintenance will allow you to get the most out of your built-up or modified BIT roof. The time that you spend planning for and doing the inspections is time well spent.