Tar and gravel roofing, also known as built-up roofing (BUR), is a classic flat roof solution chosen for its durability, cost-effectiveness, and weather resistance. This comprehensive guide examines what a tar and gravel roof is, its advantages, installation method, maintenance tips, expected lifespan, and how much a BUR roof costs in the United States. This information empowers homeowners, property managers, and commercial building owners to make informed decisions on flat roofing systems.
Summary Of Key Points About Tar And Gravel Roofs
| Aspect | Details |
|---|---|
| Type | Built-Up Roofing (BUR), Flat/Low-slope Roof System |
| Materials | Tar (asphalt or coal tar), roofing felt, gravel or mineral aggregate |
| Lifespan | 15–30 years with proper maintenance |
| Cost | $4–$7 per square foot installed (as of 2025, US average) |
| Best For | Flat and low-slope residential, commercial, and industrial roofs |
| Not Suited For | Steep-slope roofs |
What Is A Tar And Gravel Roof?
A tar and gravel roof, widely called a built-up roof (BUR), is a type of multi-layered roofing system found primarily on flat or very low-slope buildings. It consists of alternating layers of bitumen (tar or asphalt) and reinforcing fabrics, which are topped with a protective layer of gravel. This combination creates a tough, UV-resistant, and waterproof barrier, making it popular for both residential flat roofs and commercial applications in the U.S.
Components Of A Tar And Gravel Roof
A typical tar and gravel roof includes several essential materials and layers, each fulfilling a specific purpose:
- Substrate/Deck: The structural base, usually wood, steel, or concrete.
- Insulation: Rigid foam panels or board insulation to reduce energy loss.
- Bitumen (Tar/Asphalt): Acts as the adhesive and primary waterproofing agent.
- Roofing Felt/Membrane: Reinforcement layers made of fiberglass or organic materials.
- Aggregate (Gravel): Surface protection against UV, hail, and foot traffic.
How Tar And Gravel (BUR) Roofs Work
The multi-layered construction is designed for maximum protection and longevity. Each waterproof membrane of tar and felt interlocks with the next, while the gravel layer shields against weather and damage. In essence, layers of defense work together to provide a watertight, resilient rooftop suitable for varied climates and heavy use.
Main Advantages Of Tar And Gravel Roofs
- Durability: Multiple layers withstand harsh weather, foot traffic, and debris impact.
- Water Resistance: Properly installed BURs offer outstanding leak protection.
- UV Protection: The gravel layer reflects sunlight, extending roof life.
- Low Maintenance: Occasional inspections and minor repairs keep these roofs functioning well for decades.
- Affordability: BURs are often cost-effective compared to newer flat roofing systems.
- Fire Resistance: Both tar and mineral-surfaced gravel are naturally fire-resistant.
Choosing a tar and gravel roof can be ideal for budget-minded owners seeking proven performance on flat or low-slope buildings.
Potential Drawbacks To Consider
- Weight: BURs are heavy and may require structural reinforcement.
- Odor/VOCs: Hot-mopped asphalt emits strong fumes during installation.
- Installation Complexity: Requires experienced professionals for quality results.
- Ponding Water: Flat roofs are susceptible to standing water if not perfectly sloped.
- Not For Steep Slopes: Materials may slide on steep-pitched surfaces.
Weigh these cons against the benefits based on building type, budget, and local climate.
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Typical Applications In The United States
BUR tar and gravel roofs are most commonly used on:
- Commercial buildings, warehouses, and factories
- Institutional buildings like schools or hospitals
- Apartment complexes with flat rooftops
- Residential homes with flat or low-slope extensions (porches, garages)
Building codes in many U.S. states permit BUR on low-slope structures; always check with your local code authority first.
Step-By-Step Installation Of Tar And Gravel Roofs
Installing a tar and gravel roof is complex and typically performed by licensed contractors. Here are the basic steps:
- Inspection & Preparation: Check the deck for damage, ensure it can bear additional weight, and clear debris.
- Insulation Installation: Lay down rigid foam panels if required for energy efficiency.
- Applying Layers Of Felt: Lay the first bitumen-embedded roofing felt or membrane sheet.
- Hot Mopping Tar/Asphalt: Pour or mop hot tar over the felt layer.
- Repeat Layers: Alternate more layers of felt and tar, typically 3–5 plies for optimal protection.
- Adding The Gravel: When top tar layer is hot, apply mineral aggregate or gravel to embed into the tar and provide final UV and impact protection.
Proper flashing, edge finishing, and drainage slope are crucial for a trouble-free and long-lasting installation.
How Long Does A Tar And Gravel Roof Last?
With routine care and professional installation, a tar and gravel roof has an average lifespan of 15–30 years. Some well-maintained BURs on commercial buildings last even longer. Environmental factors, roof traffic, annual rainfall, and sun exposure all impact longevity.
Typical Costs Of Tar And Gravel Roofs (2025 Estimates)
| Type | Average Cost Per Sq. Ft. (Installed) | Typical Roof Size (sq. ft.) | Estimated Total Cost |
|---|---|---|---|
| Residential Flat Roof | $4 – $6 | 1,000 – 2,000 | $4,000 – $12,000 |
| Commercial Flat Roof | $5 – $7 | 5,000 – 20,000 | $25,000 – $140,000+ |
Rates may vary by state, contractor, and complexity. Always get multiple quotes and factor in tear-off/disposal of old roofing if needed.
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How To Maintain A Tar And Gravel Roof
Proper care keeps a BUR functioning optimally well beyond its warranty. Key maintenance steps include:
- Regular Inspections: Check for damage or pooling water at least twice a year, especially after storms.
- Clean Debris: Remove leaves, sticks, and trash which can trap moisture or clog drains.
- Maintain Gravel Layer: Redistribute or replace loose gravel to ensure full coverage.
- Patch Small Leaks: Immediately repair punctures, cracks, or blisters using compatible patching products.
- Maintain Flashing: Ensure that metal flashings at edges, walls, or HVAC units remain sealed and watertight.
Professional inspections and maintenance are advised annually or biannually for large or heavily-used rooftops.
Signs Of Tar And Gravel Roof Problems
- Bare Spots: Exposed felt or tar means lost protection and risk of leaks.
- Blisters Or Bubbles: Moisture trapped between layers requires prompt repair.
- Pooling Water (Ponding): Persistent puddles indicate poor drainage.
- Cracked Or Dried Out Asphalt: Aging tar loses flexibility and may fail in harsh weather.
- Leaks Or Water Stains: Find and patch any sources of interior leaks quickly.
Catch and address issues early to avoid major damage and expensive repairs.
Comparing Tar And Gravel To Other Flat Roof Systems
| Roof Type | Average Lifespan | Cost Per Sq. Ft. | Main Pros | Main Cons |
|---|---|---|---|---|
| Tar & Gravel (BUR) | 15–30 yrs | $4–$7 | Durable, fire resistant, affordable | Heavy, strong odor during install |
| Modified Bitumen | 10–20 yrs | $4–$8 | Flexible, easy repairs | Seams can split, lower impact resistance |
| EPDM Rubber | 20–30 yrs | $5–$8 | UV proof, wide panels, easy to apply | Punctures easily, seams may fail |
| TPO/PVC Membrane | 20–30 yrs | $6–$10 | Energy efficient, heat welded seams | More expensive, sensitive to installation errors |
BUR is favored for its balance of affordability, longevity, and ruggedness compared to newer roofing systems.
Frequently Asked Questions About Tar And Gravel Roofs
Can You Walk On A Tar And Gravel Roof?
Yes, but only for light, careful foot traffic—excess weight or sharp objects can disrupt the gravel layer or damage underlying membranes. Always use walkway pads or boards if regular access is needed.
How Do You Repair A Tar And Gravel Roof Leak?
First, remove gravel from the affected area, cut away damaged felt, clean the site, then apply new hot tar or compatible roofing cement. Embed new felt patch layers, reseal, and replace the gravel. For major leaks or structural issues, consult a licensed roofing contractor.
Can You Install Solar Panels On A BUR Roof?
Yes—solar arrays are often placed on flat commercial tar and gravel roofs. Ensure structural strength, protect the roofing membrane, and work with experienced solar installers familiar with flat roof mounting systems.
How Do You Know When It’s Time To Replace Your Tar And Gravel Roof?
If you observe persistent leaks, lots of bare spots, widespread blistering, or extensive cracking and gravel loss, full replacement may be more cost-effective than ongoing patch jobs. Most flat roofs need total replacement at the end of their expected service life.
Environmental Impact And Modern Alternatives
BUR systems have both positive and negative environmental implications. While bitumen production involves fossil fuels, the gravel layer improves thermal performance and reduces urban heat. Some new cold-applied asphalt and recycled-content felts are now available, making modern BURs somewhat greener than versions from previous decades. For maximum eco-friendliness, consider “cool roof” coatings or white aggregate over the BUR to reflect heat and lower energy costs.
Key Considerations Before Choosing A Tar And Gravel Roof
- Is your building structure engineered for a heavy roof system?
- Are local codes and regulations supportive of BUR installation?
- Is there adequate drainage to prevent ponding and water damage?
- Do you need a roof system with proven wind, fire, and impact resistance?
- Are you comfortable with the installation process and potential odor inconveniences during setup?
Discuss all options with a reputable local roofing expert to find the ideal match for your needs and budget.
Leading Tar And Gravel Roof Brands And Product Lines
- GAF Built-Up Roofing Systems: Offers fiberglass and polyester felt, adhesive products, and gravel surfacing options.
- Johns Manville (JM): Renowned for multi-ply BUR, insulation, and surfacing products for both commercial and residential markets.
- CertainTeed: Manufactures reliable built-up roofing plies, bitumen, and surfacing materials designed for long-term performance.
- Tamko and Firestone: Also provide compatible products and installation support for BUR systems.
Choosing materials from established manufacturers supports better warranties and ensures consistent performance.
Getting Quotes And Selecting Professional BUR Contractors
For successful BUR roof installation or repairs in the U.S., work exclusively with licensed and insured roofing contractors. Request itemized bids, ask for past project references, confirm manufacturer certifications, and check warranty terms before starting any work.
Professional installation and proper maintenance are the best ways to maximize the lifespan and value of your tar and gravel roof.
How to Get the Best Roofing Quotes
- Prioritize Workmanship
A roof is one of your home’s most important investments. Always choose a contractor based on experience and reputation — not just price. Poor installation can lead to expensive problems down the road. - Compare Multiple Estimates
Don’t settle for the first quote you receive. It’s always a smart move to compare at least three bids from local roofing professionals. You can 877-801-4315 to get local quotes from roofing contractors in your area, available across the United States. - Use Negotiation Tactics
After selecting a trusted roofer, be sure to use our proven tips — How to Negotiate with Roofing Contractors — to secure the best possible final price without cutting corners.