Tar and gravel roofs, also known as built-up roofing (BUR), have been a reliable choice for flat or low-slope roofs for over a century. This traditional roofing system consists of alternating layers of asphalt (tar) and supporting fabrics, topped with a protective layer of gravel. Understanding the costs associated with installing, maintaining, and replacing tar and gravel roofs is essential for property owners considering this option. The national average cost typically ranges from $4 to $10 per square foot installed, with most property owners spending between $4,000 and $15,000 for a complete installation, depending on size and complexity.
| Aspect | Cost Range |
|---|---|
| Installation | $4-$10 per sq ft |
| Materials Only | $1.50-$3 per sq ft |
| Labor | $2.50-$7 per sq ft |
| 1,500 sq ft Roof (Average) | $6,000-$15,000 |
| Maintenance (Annual) | $0.10-$0.30 per sq ft |
| Repair Costs | $300-$1,500 |
| Lifespan | 15-30 years |
A tar and gravel roof, more technically known as a built-up roof (BUR), is one of the oldest and most reliable flat roofing systems in the construction industry. This roofing method consists of multiple layers of roofing felt or fiberglass mat soaked and coated with hot bitumen (asphalt or coal tar). The final layer is then topped with a protective layer of gravel, small stones, or mineral granules.
The principle behind this roofing system is simple yet effective. The multiple layers of bitumen-soaked materials create a waterproof membrane, while the gravel layer serves multiple purposes. It protects the underlying layers from UV radiation, provides fire resistance, and adds weight to prevent the roof from lifting during high winds.
Tar and gravel roofs are primarily used on flat or low-slope roofs and are common in commercial buildings, apartment complexes, and some residential structures. The installation process involves alternating layers of bitumen and reinforcing fabrics, with each layer being fully adhered to the one below it.
These roofs are known for their durability, typically lasting 15-30 years depending on local climate conditions, installation quality, and maintenance practices. The multi-layer construction offers excellent waterproofing and insulation properties, making them a practical choice for many building owners despite newer alternatives in the market.
Components of a Tar and Gravel Roof
The traditional tar and gravel roof consists of several key components, each serving a specific purpose in the overall system:
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- Base Sheet or Vapor Barrier: The first layer typically installed directly on the roof deck, providing a base for the remaining layers and often functioning as a vapor barrier.
- Bitumen Layers: Multiple layers of hot asphalt or coal tar pitch that serve as the waterproofing agent. This dark, sticky substance creates the impenetrable barrier against water.
- Reinforcing Fabrics: Sheets of fiberglass, polyester, or organic felt that are embedded between the bitumen layers to provide strength and stability to the roof system.
- Surfacing Material: The top layer of gravel, crushed stone, or mineral granules that protect the underlying materials from UV damage, physical impact, and provide fire resistance.
- Flashing: Metal components installed at roof transitions, perimeters, and penetrations to prevent water infiltration at these vulnerable points.
The quality and thickness of these materials significantly impact both the performance and cost of the roof. Premium materials can increase upfront costs by 20-30% but may extend the roof’s lifespan by 5-10 years, making them a worthwhile investment for many property owners.
Installation Process
The installation of a tar and gravel roof is a labor-intensive process that requires specialized equipment and experienced professionals. The basic steps include:
- Preparation of the roof deck: Cleaning, repairing, or replacing the underlying structure to ensure a solid foundation.
- Installation of insulation: Typically rigid foam boards that provide thermal efficiency for the building.
- Application of base sheet: The initial layer is mechanically fastened or adhered to the insulation or deck.
- Application of hot bitumen: Heated to approximately 400°F and spread evenly across the base sheet.
- Embedding of reinforcing fabric: Rolled into the hot bitumen while ensuring no wrinkles or air pockets.
- Repetition of bitumen and fabric layers: Multiple layers are applied to build up the desired thickness, typically 3-5 plies.
- Application of flood coat: A final thick layer of bitumen that prepares the surface for the aggregate layer.
- Distribution of gravel or aggregate: Spread evenly at a rate of approximately 400-500 pounds per 100 square feet.
The installation process typically takes 2-5 days for an average-sized commercial roof, with timing dependent on weather conditions, roof complexity, and crew size.
Average Cost of Tar and Gravel Roofs
The cost of tar and gravel roofing varies significantly based on numerous factors, but understanding the average expenditure helps property owners budget appropriately. Nationwide, property owners can expect to pay between $4 and $10 per square foot for a complete tar and gravel roof installation. This translates to approximately $4,000 to $10,000 for a 1,000 square foot roof area.
For commercial buildings with larger roof surfaces, economies of scale often apply, potentially reducing the per-square-foot cost for very large projects. However, complex roof designs, difficult access, or removal of existing roofing systems can increase costs by 15-30% above the base rate.
When compared to other flat roofing systems, tar and gravel roofs typically represent a mid-range investment. They generally cost more than asphalt roll roofing but less than newer single-ply membrane systems like TPO or EPDM in most markets.
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Regional Price Variations
The cost of tar and gravel roofing varies significantly by location due to differences in labor rates, material availability, building codes, and climate considerations. The following table illustrates the average cost ranges across different U.S. regions:
| U.S. Region | Cost Per Square Foot | 1,500 Sq Ft Roof Total | Key Cost Factors |
|---|---|---|---|
| Northeast | $5.50-$11.00 | $8,250-$16,500 | Higher labor costs, stringent building codes, weather considerations |
| Southeast | $4.00-$8.50 | $6,000-$12,750 | Hurricane requirements in coastal areas, lower labor costs inland |
| Midwest | $4.50-$9.00 | $6,750-$13,500 | Extreme temperature variations, moderate labor costs |
| Southwest | $4.00-$8.00 | $6,000-$12,000 | UV protection needs, varied regulation by state |
| West Coast | $6.00-$12.00 | $9,000-$18,000 | Seismic considerations, strict environmental regulations, high labor costs |
| Pacific Northwest | $5.50-$10.50 | $8,250-$15,750 | Moisture resistance requirements, environmental regulations |
Urban areas generally command premium pricing compared to rural locations, with major metropolitan areas like New York, San Francisco, and Chicago often seeing prices at the upper end of these ranges. Coastal regions may incur additional costs of 10-20% due to specialized requirements for wind resistance and salt air exposure considerations.
Factors Affecting Cost
Several key factors influence the final cost of a tar and gravel roof installation:
- Roof Size and Complexity: Larger roofs may benefit from economies of scale, but complex designs with multiple penetrations, varying levels, or unusual shapes increase labor costs significantly.
- Roof Accessibility: Buildings with difficult access require additional equipment such as cranes or hoists, increasing setup and operation costs by hundreds or thousands of dollars.
- Existing Roof Condition: If an old roof needs removal, expect to add $1-$2 per square foot. Structural repairs to the deck can add $300-$500 per 100 square feet of affected area.
- Number of Layers: Traditional built-up roofs use 3-5 layers of felt or fiberglass mat. Each additional layer adds approximately $0.75-$1.50 per square foot but provides improved durability and longevity.
- Insulation Requirements: Enhanced insulation can add $1-$3 per square foot but improves energy efficiency and may qualify for rebates or incentives.
- Local Building Codes: Some jurisdictions require specific fire ratings or wind uplift resistance that may necessitate premium materials or additional installation steps.
- Contractor Demand: During peak season or following major weather events, contractor pricing may increase by 10-15% due to high demand.
- Material Quality: Premium bitumen products and aggregate can increase material costs by 20-30% but offer improved performance and longevity.
Understanding these variables helps explain the wide range in quoted prices and allows building owners to make informed decisions about their roofing investments.
Cost Breakdown for Tar and Gravel Roof Installation
Understanding the detailed cost components of a tar and gravel roof installation helps property owners evaluate quotes and budget appropriately. A typical installation involves materials, labor, equipment, and miscellaneous costs. Below is a comprehensive breakdown of these expenses for a standard commercial installation.
Materials Cost
The materials for a tar and gravel roof typically constitute 40-50% of the total project cost. The following table details the average prices for materials needed for a 1,500 square foot roof:
| Material Component | Unit Cost | Quantity Needed (1,500 sq ft) | Total Cost |
|---|---|---|---|
| Bitumen/Asphalt | $0.50-$0.75 per lb | 1,500-2,250 lbs | $750-$1,687 |
| Roofing Felt/Fiberglass Sheets | $0.15-$0.30 per sq ft per layer | 4,500-7,500 sq ft (3-5 layers) | $675-$2,250 |
| Gravel/Aggregate | $0.08-$0.15 per lb | 6,000-7,500 lbs | $480-$1,125 |
| Insulation Board | $0.50-$1.25 per sq ft | 1,500 sq ft | $750-$1,875 |
| Flashing Materials | $2.00-$4.00 per linear foot | 150-200 linear feet | $300-$800 |
| Adhesives/Primers | $30-$50 per gallon | 5-8 gallons | $150-$400 |
| Drainage Components | $50-$150 each | 4-8 units | $200-$1,200 |
| Total Materials | $3,305-$9,337 |
Material quality significantly impacts costs and performance. Premium-grade materials can increase the materials budget by 25-40% but may extend the roof’s service life by 5-10 years, representing a potential long-term value despite higher initial costs.
Labor Costs
Labor typically accounts for 45-55% of the total project cost for tar and gravel roof installation. The specialized nature of the work, safety requirements, and physically demanding conditions all contribute to the labor expense. Current industry rates include:
| Labor Category | Hourly Rate | Hours for 1,500 sq ft Roof | Total Cost |
|---|---|---|---|
| Roofing Foreman | $35-$60 | 25-35 | $875-$2,100 |
| Skilled Roofers | $25-$45 | 80-120 (2-3 workers) | $2,000-$5,400 |
| Laborers/Helpers | $18-$30 | 40-60 | $720-$1,800 |
| Total Labor | $3,595-$9,300 |
Labor rates vary significantly by geographic location, with metropolitan areas and regions with strong labor unions typically commanding higher wages. Projects completed during peak season (late spring through early fall) may incur premium rates of 10-15% due to high demand for qualified roofing crews.
Equipment Costs
Specialized equipment is necessary for tar and gravel roof installation, particularly for heating and applying the bitumen and transporting materials to the roof. These costs are typically included in the overall project price but constitute a significant portion of the overhead:
| Equipment | Typical Rental/Usage Cost |
|---|---|
| Bitumen Kettle/Heater | $150-$300 per day |
| Material Hoist/Crane | $400-$1,000 per day |
| Roof Cutter (for removal) | $75-$150 per day |
| Power Broom/Gravel Spreader | $50-$125 per day |
| Safety Equipment | $100-$300 flat fee |
| Dump Trailer (for debris) | $150-$300 per day |
| Total Equipment (3-5 day project) | $1,200-$3,500 |
Difficult access situations may require specialized equipment such as larger cranes or pumping systems that can add $1,000-$2,500 to the equipment costs for a typical installation.
Permits and Inspection Fees
Permit requirements vary widely by location, but most commercial roofing projects require building permits and inspections. These administrative costs typically include:
- Building Permits: $300-$1,000 depending on project value and location
- Inspection Fees: $150-$500 for required inspections
- Possible Architectural Review: $0-$750 in areas with strict aesthetic guidelines
Some jurisdictions may require additional permits for equipment placement on public streets or sidewalks, adding $100-$500 per day in urban areas.
Tar and Gravel Roof vs. Other Roofing Options
When considering a tar and gravel roof, property owners should understand how this traditional system compares with other flat roofing options in terms of cost, performance, and longevity. This comparison helps determine the best value for specific building needs and budget constraints.
Comparative Cost Analysis
The following table compares initial installation costs, lifespan, and long-term value of various flat roofing systems:
| Roofing System | Installation Cost (per sq ft) | Average Lifespan | 30-Year Cost of Ownership | Best Applications |
|---|---|---|---|---|
| Tar and Gravel (BUR) | $4.00-$10.00 | 15-30 years | $8.00-$20.00 | Large commercial buildings, traditional construction |
| Modified Bitumen | $4.50-$9.50 | 15-25 years | $9.00-$19.00 | Medium-sized commercial, improved installation safety |
| EPDM (Rubber) | $5.50-$9.50 | 20-30 years | $7.50-$14.25 | Large open roofs, cold climates |
| TPO | $6.00-$11.00 | 15-25 years | $9.00-$22.00 | Energy-efficient buildings, white reflective surface |
| PVC | $7.50-$13.00 | 20-30 years | $10.00-$19.50 | Chemical resistance, restaurants, industrial facilities |
| Spray Polyurethane Foam | $6.00-$12.00 | 15-30 years | $8.00-$24.00 | Irregular shapes, enhanced insulation needs |
The 30-year cost of ownership considers initial installation, expected maintenance, and replacement costs over a three-decade period. Tar and gravel roofs often provide competitive long-term value despite requiring more maintenance than newer single-ply systems, particularly for buildings where roof traffic or mechanical equipment access is expected.
Strengths and Limitations
Understanding the advantages and disadvantages of tar and gravel roofing helps property owners make informed decisions:
Strengths of Tar and Gravel Roofs:
- Excellent waterproofing with multiple redundant layers
- Superior puncture and damage resistance from the gravel layer
- Good fire resistance ratings
- Effective thermal mass that moderates temperature fluctuations
- Proven track record over more than a century
- Familiar system for most contractors ensuring quality installation
Limitations of Tar and Gravel Roofs:
- Heavier than alternative systems, requiring strong structural support
- More labor-intensive installation
- Challenging to locate leaks when they occur
- Higher VOC emissions during installation
- Less environmentally friendly than newer alternatives
- Limited slope applications (generally only for slopes under 2:12)
These characteristics make tar and gravel roofs particularly well-suited for large commercial buildings with adequate structural support and regular maintenance programs, while smaller buildings or those seeking maximum energy efficiency might benefit from newer roofing technologies.
Maintenance Costs for Tar and Gravel Roofs
Proper maintenance is crucial for maximizing the lifespan and performance of a tar and gravel roof. While these roofing systems are durable, they require regular attention to prevent costly issues. Understanding the maintenance expenses helps property owners budget appropriately for the roof’s full lifecycle.
Routine Maintenance Expenses
Regular maintenance is essential for tar and gravel roofs and typically includes the following annual or semi-annual services:
| Maintenance Service | Frequency | Cost Range | Purpose |
|---|---|---|---|
| Professional Inspection | 1-2 times annually | $250-$500 per inspection | Identify potential issues before they cause damage |
| Debris Removal | 2-4 times annually | $0.10-$0.20 per sq ft | Prevent drainage issues and organic matter accumulation |
| Drain/Gutter Cleaning | 2-4 times annually | $100-$300 per service | Ensure proper water drainage |
| Gravel Redistribution | Annually | $0.15-$0.30 per sq ft | Maintain UV protection and ballast distribution |
| Minor Repairs | As needed | $300-$800 annually | Address small issues before they expand |
| Annual Maintenance Total | $0.50-$1.25 per sq ft annually |
Proactive maintenance typically saves 25-50% on long-term roofing costs by preventing major damage and extending the roof’s functional lifespan. Buildings in areas with extreme weather conditions or abundant vegetation may require additional maintenance services, increasing annual costs by 15-30%.
Repair Costs for Common Issues
Even well-maintained tar and gravel roofs may develop issues that require targeted repairs. The most common problems and their associated repair costs include:
| Common Issue | Repair Cost | Repair Process | Prevention Measures |
|---|---|---|---|
| Alligatoring (Surface Cracking) | $2-$4 per sq ft | Application of bitumen emulsion coating | Regular inspections, UV-resistant surfacing |
| Blistering | $3-$6 per sq ft | Cut and patch affected areas | Proper ventilation, quality installation |
| Flashing Failure | $8-$15 per linear foot | Remove and replace flashing | Quality materials, proper installation techniques |
| Ponding Water | $5-$10 per sq ft of affected area | Build up low areas or install additional drainage | Proper slope design, regular cleaning of drains |
| Membrane Punctures | $300-$600 per repair | Patch with bitumen and reinforcing fabric | Walkway pads, restricted roof access |
| Gravel Loss | $0.50-$1.00 per sq ft | Add new aggregate to exposed areas | Proper initial application, wind barriers |
Most commercial buildings with tar and gravel roofs require some repair work every 3-5 years, with the average repair bill ranging from $1,000-$3,000 per incident. Addressing repairs promptly typically reduces costs by 40-60% compared to allowing problems to worsen and cause additional damage to the roof system or building interior.
Replacement vs. Repair Costs
As a tar and gravel roof ages, property owners often face the decision between continued repairs or complete replacement. This decision has significant financial implications and depends on several factors including the roof’s current condition, age, and the building’s long-term plans.
When to Repair vs. Replace
Making the right decision between repair and replacement involves evaluating several key factors:
| Factor | Favor Repair | Favor Replacement |
|---|---|---|
| Roof Age | Less than 15 years old | Over 20 years old |
| Damage Extent | Less than 25% of roof area affected | More than 30% of roof shows deterioration |
| Leak Frequency | Isolated, infrequent leaks | Multiple recurring leaks |
| Energy Costs | No significant increase in energy bills | Rising heating/cooling costs |
| Building Plans | Property sale or renovation planned within 5 years | Building to be maintained long-term |
| Repair History | First major repair needed | Multiple previous repairs |
| Budget Constraints | Limited immediate capital available | Financing options available for capital improvement |
Industry experts suggest the “50% rule” as a general guideline: if repair costs exceed 50% of replacement costs, replacement is typically more economical in the long run. However, this must be considered alongside other factors such as business disruption and building occupancy plans.
Complete Replacement Breakdown
A full tar and gravel roof replacement involves several distinct phases, each with associated costs:
| Replacement Phase | Cost Component | Percentage of Total |
|---|---|---|
| Tear-off and Disposal | $1.50-$3.00 per sq ft | 15-25% |
| Deck Inspection and Repair | $0.50-$2.00 per sq ft (if needed) | 5-15% |
| Insulation Installation | $1.00-$2.50 per sq ft | 10-20% |
| New Roof System Installation | $4.00-$7.00 per sq ft | 40-50% |
| Flashing and Detail Work | $1.00-$2.00 per sq ft | 10-15% |
| Total Replacement Cost | $8.00-$16.50 per sq ft | 100% |
The wide price range reflects variations in building height, accessibility, regional costs, and material selections. Multi-story buildings typically incur an additional 15-25% in costs due to the logistical challenges of material transport and safety requirements.
Factors That Influence Tar and Gravel Roof Costs
Beyond the basic materials and labor expenses, several key factors can significantly impact the final cost of a tar and gravel roofing project. Understanding these variables helps property owners anticipate potential cost adjustments and make informed decisions about their roofing investments.
Roof Size and Complexity
The size and design of a roof directly influence installation costs in several ways:
| Roof Characteristic | Cost Impact | Reason |
|---|---|---|
| Overall Size | Larger roofs generally cost less per square foot | Economies of scale in setup, equipment, and labor efficiency |
| Number of Penetrations | Each penetration adds $150-$500 to total cost | Required detail work around vents, pipes, HVAC, etc. |
| Roof Shape | Complex shapes increase costs by 15-30% | More cutting, fitting, and detail work required |
| Multiple Levels | Each level transition adds $10-$25 per linear foot | Additional flashing, material transitions, and labor |
| Perimeter Length | Higher ratio of perimeter to area increases costs | More edge detail work required per square foot of roof |
Buildings with numerous rooftop units, vents, or other penetrations can see total costs increase by 10-20% compared to open, unobstructed roof areas of the same size. This cost difference reflects the additional labor and materials needed to ensure proper flashing and waterproofing around these critical junctures.
Accessibility Issues
Site conditions and building characteristics that affect roof access can significantly impact project costs:
| Access Factor | Cost Premium | Solution |
|---|---|---|
| Building Height (over 3 stories) | 10-30% increase | Additional equipment, safety measures, material transport systems |
| Limited Staging Area | 5-15% increase | Remote staging with shuttling materials, specialized delivery methods |
| Limited Roof Access Points | 5-10% increase | Material transport over longer distances on the roof surface |
| Occupied Building Requirements | 5-20% increase | Work hour restrictions, additional protection measures, phased implementation |
| Urban Location/Tight Site | 10-25% increase | Street permits, traffic control, crane setup, limited working hours |
These accessibility factors primarily affect labor costs and equipment requirements. For example, buildings in dense urban environments may require street closure permits costing $500-$1,500 per day in addition to specialized material delivery systems.
Cost-Saving Tips for Tar and Gravel Roofing
While tar and gravel roofing represents a significant investment, several strategies can help property owners maximize value and reduce overall costs without compromising quality or performance. These approaches address timing, materials, contractor selection, and maintenance practices.
Timing Your Installation
Strategic timing of a roofing project can yield substantial cost savings:
| Timing Strategy | Potential Savings | Considerations |
|---|---|---|
| Off-Season Installation (Late Fall/Winter) |
10-15% | Weather constraints may extend project timeline; some materials require minimum temperatures |
| Advance Scheduling (3-6 months ahead) |
5-10% | Contractors can optimize crew scheduling and material procurement |
| Combining with Other Building Work | 5-15% | Shared mobilization costs, scaffolding, and equipment with other projects |
| Multi-Building Projects | 10-20% | Economies of scale for property managers with multiple buildings |
The roofing industry typically experiences peak demand from late spring through early fall, with premium pricing during these months due to high demand. Planning non-emergency work for shoulder seasons can result in better contractor availability and more competitive pricing.
Contractor Selection Advice
Choosing the right roofing contractor significantly impacts both cost and quality:
- Obtain Multiple Detailed Bids: Solicit 3-5 proposals from established roofing contractors, ensuring each bid specifies materials, labor, timeline, warranty terms, and payment schedule. This competitive process typically yields 5-15% savings.
- Verify Credentials and Experience: Select contractors with specific experience in tar and gravel roofing, proper insurance coverage, manufacturer certifications, and positive references. Reputable contractors may charge 10-15% more initially but often save money through quality installation.
- Negotiate Payment Terms: Structure payments to align with project milestones rather than front-loading costs. This approach improves cash flow and provides leverage to ensure quality completion.
- Consider Maintenance Agreements: Some contractors offer reduced installation pricing when combined with multi-year maintenance contracts, potentially saving 5-10% on the initial installation.
- Evaluate Total Value, Not Just Price: The lowest bid can result in 25-40% higher lifetime costs if poor installation leads to premature failure or frequent repairs. Review warranty terms, materials quality, and installation methods when comparing bids.
Companies specializing specifically in commercial flat roofing often provide better value than general roofing contractors for tar and gravel roof installations due to their specialized equipment and experienced crews.
Hiring a Contractor for Tar and Gravel Roofing
Selecting the right roofing contractor is arguably the most important decision in the roofing process. Quality installation is essential for performance and longevity, making contractor selection a critical factor in the overall value equation.
Getting Estimates
The estimating process provides valuable insights into contractor professionalism and attention to detail:
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.
| Estimation Element | What to Look For | Red Flags |
|---|---|---|
| Site Inspection | Thorough examination of the entire roof, including structure | Estimates provided without physical inspection |