Are you considering roofing options for your flat or low-slope home? Tar and gravel roofs, also known as Built-Up Roofs or BURs, might be exactly what you need.
These multi-layer roofing systems have been protecting homes and commercial buildings for over a century, and there’s a good reason they’re still popular today.
If you’re dealing with a flat roof replacement or building a new home with low-slope areas, you’ve probably heard mixed opinions about tar and gravel systems.
Some people swear by their durability, while others worry about maintenance.
In this guide, we’ll walk you through the real benefits, ongoing care requirements, and important factors you should consider before making your decision.
What is a Tar and Gravel Roof?
A tar and gravel roof is a multi-layer system that has protected buildings for over 100 years. It works like a sandwich with roofing felt or fiberglass mats as the foundation, hot asphalt between each layer for waterproofing, and gravel on top for protection against weather and UV rays.
This system, also called Built-Up Roofing or BUR, creates multiple protective layers, so if one gets damaged, others continue protecting your home.
The gravel reflects sunlight to keep homes cooler and provides weight to prevent wind uplift.
Modern versions use improved materials like modified asphalt that stays flexible in cold weather, while some use ballast systems with loose stones over a single rubber membrane.
Benefits of a Tar and Gravel Roof
Durability and Longevity
The multi-layered system resists cracking, blistering, and weather damage better than single-layer alternatives. You can expect 20 to 25 years or more of protection with proper maintenance.
Waterproofing and Weather Protection
Gravel shields the asphalt from UV rays, hail, and heavy rain while multiple asphalt layers create backup waterproofing. Even if the top layer gets damaged, you still have protection underneath.
Fire Resistance
The gravel surface provides a Class A fire rating, the highest level available. This safety feature gives peace of mind and may lower insurance premiums.
Thermal Performance
Gravel regulates roof temperature by absorbing heat during the day and releasing it at night. This improves energy efficiency and aids water evaporation after rain.
Maintenance and Repair Advantages
Gravel provides safe walking traction for inspections and traps debris that might clog drains. Damage can often be fixed with localized patching rather than full section replacement.
Gravel: More Than Just Aesthetic
Protective Gravel on BUR
The gravel on Built-Up Roofs serves a critical protective function. Small, pea-sized stones get embedded into the final asphalt flood coat, creating a tough protective shell.
This gravel layer shields your roof from harmful sunlight and daily weathering that would otherwise break down the asphalt.
Ballast Gravel on Single-Ply Roofs
Single-ply membrane systems use larger stones, typically 1 to 2 inches in size, that sit loose on top of the rubber membrane.
These bigger stones provide the weight needed to hold the membrane in place and protect it from wind uplift during storms.
Considerations Before Choosing a Tar and Gravel Roof
Roof Slope and Structure
Tar and gravel roofs only work on flat or low-slope surfaces. If your roof has a steep pitch, this system won’t be suitable for your home.
The weight of multiple asphalt layers plus gravel creates a heavier system than other roofing options.
Climate and Environment
Consider your local weather conditions carefully before choosing this roofing system. Areas with extreme snow loads, heavy rainfall, or frequent ponding water can create problems for tar and gravel roofs.
Strong winds and severe storms may wash gravel off your roof, requiring replacement.
Installation and Costs
Proper installation requires experienced contractors who understand the complexities of multi-layer roofing systems.
Not every roofer has the skills or equipment needed for quality tar and gravel installation. While the upfront costs may be higher than some alternatives, the long lifespan makes it cost-effective over time.
Maintenance Tips for Longevity
- Regular Inspections: Check twice yearly for cracks, loose gravel, and water pooling. Look for blisters, tears, or thin, gravelly areas.
- Apply Reflective Coatings: Add protective coatings every few years to boost durability and energy efficiency while preventing UV damage.
- Keep Detailed Documentation: Take photos and maintain records of repairs and maintenance for insurance claims and tracking roof health.
- Address Problems Quickly: Fix leaks, cracks, and damage immediately. Small problems become expensive repairs when ignored.
When a Tar and Gravel Roof May Not Be the Best Choice
Tar and gravel systems simply don’t work on roofs with steep slopes since the gravel will slide off, and asphalt layers won’t adhere properly to angled surfaces.
In extremely hot climates, these roofs can struggle when gravel coverage becomes inadequate, as exposed asphalt softens and deteriorates quickly under intense temperatures.
Areas with frequent heavy snow or rainfall also present challenges, as snow can create ice dams, excessive water causes ponding that leads to membrane failure, and heavy precipitation washes gravel away, leaving your roof vulnerable to weather damage.
Conclusion
Tar and gravel roofs offer compelling advantages that make them worth serious consideration for your flat or low-slope home.
The durability of multiple protective layers, excellent waterproofing capabilities, superior fire resistance, and straightforward maintenance requirements create a roofing system that truly delivers value over decades.
However, this isn’t a DIY project or a job for inexperienced contractors. The success of your tar and gravel roof depends entirely on proper installation and quality materials.
Always work with professional contractors who specialize in built-up roofing systems and can show you examples of their previous work.
If you’re facing a flat roof replacement or building a new low-slope home, don’t overlook this time-tested option.
The upfront investment pays dividends through years of reliable protection and lower long-term costs.
Frequently Asked Questions
How long does a tar and gravel roof typically last?
A properly installed system lasts 20 to 25 years or more with regular maintenance. The multi-layer design provides excellent durability.
Can tar and gravel roofs be installed on any type of building?
These roofs work only on flat or low-slope structures. Steep-pitched roofs cannot support this system.
What maintenance does a tar and gravel roof require?
Regular inspections twice yearly and prompt repair of damage. Occasional gravel replacement and protective coatings help extend lifespan.
Are tar and gravel roofs more expensive than other flat roofing options?
Initial costs may be higher, but the long lifespan makes them cost-effective over time. Fewer replacements reduce total investment.
Do tar and gravel roofs provide good energy efficiency?
Yes, the gravel layer regulates temperature and reflects sunlight effectively. This can reduce cooling costs and improve energy performance.
