Asphalt built up roofing, commonly referred to as BUR roofing, is a durable, multi-layer system widely used on commercial and industrial buildings. This guide explains what BUR is, how it is installed, typical materials, maintenance needs, and factors that influence performance and cost. It highlights best practices for selecting, installing, and maintaining asphalt built up roofs to maximize longevity and protect interior spaces from weather damage.
What Is Asphalt Built Up Roofing?
Asphalt built up roofing is a multi-ply system constructed by alternating plies of reinforcing fabric (such as fiberglass or organic felt) with asphalt binders. The final surface typically receives a protective gravel or mineral surfacing. This layered design provides superior waterproofing, UV protection, and durability against weathering. BUR roofs commonly serve flat or low-slope roofs in commercial settings and can be tailored for various climates with specific asphalt grades and surfacing choices.
Materials And System Variants
Key components include:
- Asphalt Binders: On felts or fabrics, oxidized or polymer-modified asphalts improve durability and weather resistance.
- Reinforcements: Fiberglass or organic felts add tensile strength and puncture resistance.
- Ply Count: Typical installations use 3 to 5 plies, with more plies for severe exposure or steeper slopes.
- Surfacing: Gravel, mineral granules, or reflective coatings protect against UV degradation.
- Waterproofing Barrier: A final asphalt layer or cap sheet seals joints and edges.
Variants include:
- Modified BUR (MBR): Uses polymer-modified asphalt for enhanced elasticity and crack resistance.
- Built-Up Roof With Cap Sheet: Adds a durable cap sheet over the final ply for improved protection and ease of repair.
Installation Process And Best Practices
Installation typically follows these steps, performed by qualified roofing professionals:
- Surface Preparation: Clean the deck, repair any damage, and ensure proper drainage.
- Primer Application: Apply a compatible primer to enhance adhesion between layers.
- Ply Installation: Install reinforcing plies with hot or cold asphalt adhesive, ensuring full bedding and edge alignment.
- Surfacing: Apply gravel or mineral surfacing to protect the membrane and reflect solar heat.
- Quality Checks: Inspect for laps, blisters, and pinholes; perform water testing where required.
Proper ventilation and fire safety are essential during installation. Local building codes may require permits and inspections, especially for retrofit BUR systems.
Maintenance And Longevity
BUR roofs offer long service life when maintained. Routine actions include:
- Regular Inspections: Schedule biannual checks and after severe storms to identify membrane damage or ballast displacement.
- Cleaning And Debris Removal: Keep gutters clear to prevent water backing and edge deterioration.
- Ponding Water Mitigation: Address any low spots that hold water to prevent accelerated aging.
- Repair Strategies: Punctures, splits, or lifted edges should be repaired promptly with compatible asphalt, fabric patches, and sealants.
- Ballast Replacement: Reposition or replace gravel ballast if it becomes uneven or dislodged.
BUR roofs are sensitive to extreme temperature fluctuations. Regular maintenance helps preserve membrane integrity, extend life expectancy, and maintain energy efficiency when reflective coatings are used.
Durability, Weather Resistance, And Climate Considerations
The layered design provides robust waterproofing and wind uplift resistance when properly installed. BUR roofs perform well in a range of climates, but performance depends on:
- Aspiration To Water: Proper slope and drainage reduce standing water and edge failures.
- Asphalt Type: Polymer-modified asphalts improve elasticity in cold weather and resilience in heat.
- Surfacing: Gravel weight and wind resistance protect against UV and weathering; reflective coatings can improve energy efficiency.
- Expansion And Contraction: The ply arrangement accommodates movement, reducing crack formation when installed with appropriate joints.
Environmental And Energy Considerations
BUR systems can contribute to sustainability goals when designed with eco-friendly materials and practices. Recycled content in felts and reinforcing fabrics, as well as reflective surfacing, can reduce urban heat island effects. However, disposal and recycling of asphalt components should follow local regulations. Contractors may offer cool roof coatings to lower cooling loads, particularly in hot climates.
Cost, Life Cycle, And Return On Investment
Initial costs for asphalt built up roofing vary with ply count, materials, deck condition, and regional labor rates. A typical BUR system offers a long life span, often 20 to 40 years with maintenance. Life cycle considerations include energy savings from reflective surfacing and the cost of periodic re-coating or ballast maintenance. When comparing to single-ply systems, BUR may provide superior durability and older buildings with complex profiles might benefit from BUR’s versatility.
Safety, Codes, And Warranty Considerations
Professional installation is essential for safety and performance. Local codes govern fire ratings, wind uplift, and roofing material approvals. Many BUR systems offer strong warranties covering membrane performance, ballast integrity, and workmanship. Prospective buyers should review warranty terms, reserve funds for maintenance, and ensure crews hold appropriate certifications for hot-applied asphalt work and ballast handling.
Replacement And Retrofit Considerations
When a BUR system nears the end of its service life or requires extensive repairs, alternative options may be considered. A full replacement with a newer BUR installation or a switch to a modern single-ply system could be evaluated based on building use, desired energy efficiency, and roof geometry. A professional assessment helps determine whether a re-cover, re-coating, or complete tear-off best meets performance goals and budget.
Frequently Asked Questions
- How long does an asphalt built up roof last? Typical life spans range from 20 to 40 years, depending on maintenance, installation quality, and climate.
- What maintenance is required? Regular inspections, debris removal, and timely repairs extend life and prevent leaks.
- Is BUR energy efficient? Reflective surfacing and proper insulation can improve energy performance and reduce cooling costs.