These roofs are the traditional approach to flat
commercial or industrial roofing in North America. Multiple layers of felt
with interply moppings of asphalt or coal tar are assembled in the field to
"build up" a finished roof assembly. A heavy application of’ asphalt or coal
tar which is then covered with gravel is the typical surface finishing to
these assemblies, primarily for fireproofing purposes.
These roof assemblies have a good life expectancy,
normally in the range of 15 to 25 years. Built-up roofs were very popular
until the I 970’s, enjoying better than 90% of the roofing
market. For a variety of reasons BUR’s experienced a decline in the market to
approximately a 40% share in 1989. Significant improvements in materials, and
a better understanding of proper application techniques have resulted in
significant gains in overall performance as well as market share.
Approximately 55%
of the commercial roofing market is now BUR again.
Coal tar BUR’s are best utilized when roof areas have a very low slope and
ponding water is probable. Coal tar is completely impervious to ponding water,
one of the few roofing materials that has that attribute. Coal tar also has a
low melting point, which means in the summer months, the coal tar becomes
fluid and will "self heal".
Asphalt BUR’s are best utilized when roof areas have significant slope
where the low melting point of coal tar might cause "slippage" of the
membrane. Normally any roof system which has in excess of 1/4" per running
foot of slope should utilize asphalt if the building owner wishes to utilize a
built- up system. Asphalt roofs can also be built in a "smooth surface"
installation if the finished surfacing
of gravel is undesirable to a client.
Modified Bitumen roof systems with
quality installations performed by FixaRoof
