Tar and gravel roofs, also known as built-up roofs (BUR), have been a popular and reliable choice for flat and low-slope commercial and residential buildings for over a century. Composed of multiple layers of asphalt-impregnated felt or fiberglass mats alternated with layers of bitumen (the “tar”) and topped with a protective layer of gravel or slag, these roofs are prized for their durability, fire resistance, and excellent waterproofing capabilities. However, like any roofing system, they are not immune to the effects of time and weather. Understanding the process and importance of tar and gravel roof repair is essential for maintaining the integrity of your building and protecting your investment.
The primary function of the gravel surface on a tar and gravel roof is multifaceted. It protects the underlying asphalt layers from the sun’s destructive ultraviolet (UV) rays, which can cause the tar to become brittle and crack over time. The gravel also provides crucial ballast, helping to hold the roof system in place against wind uplift, and acts as a fire-resistant layer. Furthermore, it adds a durable walking surface for maintenance. When this system is compromised, timely repair is critical to prevent minor issues from escalating into major, costly problems like interior water damage or structural deterioration.
Recognizing the signs that your tar and gravel roof needs attention is the first step in the repair process. Common indicators include visible cracks or splits in the asphalt surface, areas where the gravel has worn away completely (known as bald spots), pooling water that does not drain within 48 hours, and leaks or water stains on interior ceilings. Blisters, which are bubbles that form when trapped moisture or air expands, are another frequent issue. Regular bi-annual inspections, particularly after severe weather events, are crucial for early detection.
The repair process for a tar and gravel roof is specialized and typically follows these key steps:
- Inspection and Assessment: A qualified roofing professional will first conduct a thorough inspection to identify all areas of concern. This involves carefully brushing aside the gravel in suspect areas to examine the condition of the underlying tar and felt layers.
- Surface Preparation: The repair area must be meticulously cleaned. All loose gravel, dirt, and debris are removed. Any wet or damaged insulation underneath must also be identified and replaced to ensure the roof’s thermal performance and structural integrity.
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Repair Execution: The specific repair method depends on the problem identified:
- Patching Bald Spots: For areas where gravel has eroded, new asphalt is applied to the exposed area, and fresh gravel is embedded into it to restore UV protection.
- Sealing Cracks and Splits: Cracks are cleaned out, and a roofing cement or a new layer of asphalt-saturated fabric is applied over the crack, sealed with a coating of asphalt.
- Fixing Blisters: Blisters are carefully cut open in a cross pattern, the layers are peeled back to allow moisture to escape, and the area is dried. New asphalt is then applied, and the felt layers are resealed before being covered with gravel.
- Addressing Flashing Failures: The metal flashing around roof penetrations like vents, pipes, and walls is a common failure point. Old caulking and sealant are removed, and new flashing cement or membrane is installed to create a watertight seal.
- Flood Coat and Re-graveling: For larger repairs or overall roof restoration, a new “flood coat” of hot asphalt may be applied over the entire roof surface. While the asphalt is still hot, a new, even layer of gravel is spread across it, embedding itself to form a new protective surface.
While some property owners may consider do-it-yourself repairs for small issues, tar and gravel roof repair is generally a job best left to professionals. The work involves handling hot asphalt, which requires specialized equipment and poses significant safety risks, including burns and fire hazards. Professionals have the experience to accurately diagnose problems that may not be visible to an untrained eye and can ensure that repairs are completed in a way that maintains the roof’s warranty and longevity.
The cost of tar and gravel roof repair can vary widely based on several factors, including the extent of the damage, the size of the roof, its accessibility, and regional labor rates. Minor patching may cost a few hundred dollars, while a full restoration involving a new flood coat and gravel can run into the tens of thousands. However, this investment is almost always more economical than a full roof replacement, which can be two to three times more expensive. Proactive maintenance and repair can dramatically extend the life of a tar and gravel roof, which can often last 20 to 30 years or more when properly cared for.
Beyond immediate repairs, implementing a routine maintenance program is the most effective strategy for maximizing the lifespan of your roof. This includes keeping drains and scuppers clear of debris to prevent water pooling, trimming overhanging tree branches to minimize debris accumulation and physical damage, and scheduling professional inspections at least twice a year. A small investment in preventative maintenance can save tens of thousands of dollars in premature replacement costs.
In conclusion, a tar and gravel roof is a durable and effective roofing system, but it is not maintenance-free. Understanding the common signs of wear and the essential steps involved in tar and gravel roof repair empowers property owners to make informed decisions. By addressing issues promptly through professional assessment and repair, and by committing to a consistent maintenance schedule, you can ensure your tar and gravel roof continues to provide reliable protection for your property for decades to come, safeguarding your investment and avoiding the much larger expense of a full roof replacement.