Build-up Roofs a Longtime Staple for Florida Commercial Buildings

By Rick Brown • November 16th, 2011

Built-up roofs using coal tar pitch are the oldest form of flat roofing in existence. One hundred forty year old sketches are available showing horse drawn “hot kettles” and this form, with minimal changes, is still in use today in Tampa Bay and all of Florida.

Coal tar pitch is a distillate of coal tar and is formed of primarily aromatic hydrocarbons. This complex linking makes coal tar inherently stable chemically and allows a broad range of softening temperatures vs. the defined melting point found in asphalt products. In short, coal tar is an extremely durable roof membrane which softens at very low temperatures and this cold flow property allows the roof to “heal” itself from minor punctures and voids.

Coal tar roof systems consist of alternating layers of roofing pitch with reinforcing felts and are “built-up” in a similar fashion to asphalt BUR roofs. Because of the unique chemical composition of coal tar, it can be installed on “dead level” or poorly drained flat roofs with no ill effects on the system. Prior to the widespread use of mechanical air conditioning units, many buildings were “water cooled” by providing raised edge details to impede water run-off and coal tar pitch was the roof system of choice for these locations.

Coal tar pitch is also utilized in several other areas of the construction industry including a below grade waterproofing mastic and pavement sealants.

Unfortunately, the past few decades have revealed some serious health concerns with coal tar products. Side effects from the vapors range from minor skin, nose and throat irritation to nosebleeds, changes in skin pigmentation, rashes, fainting and comas.

Additionally, the price of pitch has been a prohibitive factor as the installation cost is typically 2-3 times that of asphalt products and special design criteria must be met to accommodate the cold-flow characteristics.

The combination of health and cost concerns has created a marked decrease in the cold tar market. Several manufacturers’ have vacated this segment of the industry and as health insurance costs continue to rise, we’re doubtful coat tar pitch will rebound.

If you have a coal tar roof on your building and require assistance in managing this specialized system, call All Area Roofing & Waterproofing, Inc. today..

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