Built Up Roof Section: A Comprehensive Guide to BUR Systems

Built Up Roof (BUR) systems, commonly known as built up roofing, are a time-tested solution for flat and low-slope roofs. This article explains BUR components, installation, benefits, maintenance, and how to choose a contractor. Relevant keywords include built up roof, BUR, built up roofing, and flat roof waterproofing, helping property owners and managers understand why BUR remains popular in American construction.

What Is A Built Up Roof (BUR) System

Definition and purpose: A Built Up Roof (BUR) is a multi-ply roofing assembly that uses alternating layers of reinforcing fabric and bituminous material to create a durable, waterproof surface. The final surface is protected by a gravel or coating layer. The design provides redundancy against leaks and excellent waterproofing performance for low-slope roofs.

Common configurations: BUR assemblies typically combine 3 to 5 plies of reinforcement felt with hot-applied asphalt or coal tar. Each ply adds strength and impermeability, while the top membrane reduces ultraviolet exposure and weathering effects. The system is well-suited to commercial, institutional, and industrial buildings in the United States.

Key Components Of Built Up Roof Systems

The durability of a BUR is tied to its layered construction. Typical components include:

• Felt Or Ply Sheets: Glass-fiber or organic felts provide reinforcement and dimensional stability for each ply.
• Bituminous Membrane: Hot-applied asphalt, coal tar, or other bitumen binds the reinforcing plies and provides waterproofing.
• Interply Adhesives: Asphalt or synthetic adhesives bond plies and improve seam integrity.
• Cap Sheet: A reflective or mineral-surfaced cap sheet protects the BUR from UV exposure and weathering.
• Protection Layer: Gravel, gravel substrate, or reflective coatings safeguard the surface and extend life.
• Waterproofing Redundancy: Multiple plies create redundancy, reducing the chance of localized leaks spreading.

Advantages Of Built Up Roof Systems

• Proven Waterproofing: Multiple plies provide robust protection against leaks on low-slope roofs.
• Durability: BURs resist punctures, hail, and foot traffic when properly installed and maintained.
• Versatility: Compatible with various insulation types and roof shapes; suitable for retrofits and new builds.
• Proven Longevity: With proper maintenance, BUR systems can exceed 20 to 30 years of service life.
• Thermal Performance: Cap sheets and reflective coatings can reduce cooling loads in hot climates.

Limitations And Considerations

• Weight: BUR is heavier than single-ply roofs, affecting structure design and load calculations.
• Cost: Initial installation costs are higher than some other membranes, though long-term durability adds value.
• Maintenance Needs: Periodic inspections, resealing seams, and gravel replacement may be required.
• Environmental Impact: Bitumen materials have embodied energy considerations; newer BUR designs aim to reduce environmental footprint.

Installation Process For Built Up Roofs

Proper BUR installation requires skilled workmanship and adherence to local codes. Typical steps include:

1. Surface Preparation: Clean the substrate, repair any structural issues, and ensure proper drainage.
2. Insulation And Deck Preparation: Install suitable insulation and a stable substrate for ply adhesion.
3. Formation Of Plys: Apply reinforcing plies with suitable adhesive or hot asphalt, placing each ply in a staggered pattern.
4. Main Plies: Add multiple layers to achieve the desired thickness and waterproofing capacity.
5. Cap Sheet And Protection: Install the cap sheet and surface protection (gravel or coating) as specified.
6. Flashing And Detailing: Seal edges, penetrations, and parapets to prevent leaks at joints.
7. Quality Assurance: Conduct post-installation inspections and perform any required testing.

Maintenance And Common Issues

Routine maintenance preserves BUR performance. Key practices include:

• Regular Inspections: Check seams, flashings, and the cap surface after severe weather.
• Vegetation And Debris Control: Remove debris that can trap moisture or cause drainage problems.
• Surface Repairs: Reseal or replace worn cap sheets or damaged plies promptly to prevent leaks.
• Drainage Management: Ensure clear drainage paths and proper slope to avoid ponding water.
• UV Protection: Maintain reflective coatings or gravel to minimize UV degradation.

Design Considerations For BUR Selection

Choosing a BUR system depends on climate, building use, and budget. Consider:

• Climate: Severe weather regions benefit from multi-ply BUR with strong waterproofing.
• Insulation Needs: BUR can be paired with various insulation types to meet R-value targets.
• Maintenance Capacity: Ongoing maintenance capabilities influence the expected life span.
• Code Requirements: Local fire, wind, and energy codes may affect material choices and installation methods.

Environmental And Safety Considerations

BUR systems have environmental and safety implications. Practices include:

• Material Choices: Use low-emission bitumen and recycled content felts where available.
• Waste Management: Recycle or responsibly dispose of old BUR materials during retrofits.
• Worker Safety: Follow OSHA guidelines for hot-mapplied asphalt and heavy equipment operation.
• Fire Safety: Proper handling of hot asphalt and open flames during installation is essential.

Contractor Selection And Project Planning

Choosing the right contractor ensures BUR performance. Focus on:

• Experience: Look for installers with extensive BUR portfolios and local project references.
• Licensing And Insurance: Confirm proper licensing, insurance, and bonding for risk management.
• Warranty Terms: Understand coverage for workmanship and material defects, and the duration.
• Maintenance Plan: Request a post-installation maintenance schedule and inspection frequency.
• Detailed Proposal: Obtain a written scope, thickness, materials, and performance metrics.

Cost Considerations And Life-Cycle Value

Cost factors for built up roofs include material quality, ply count, insulation, and labor. A higher initial investment often translates to:

• Lower Long-Term Maintenance:Fewer repairs due to robust waterproofing.
• Extended Service Life: Potentially longer intervals between re-roofing projects.
• Energy Savings: Reflective cap sheets can reduce cooling loads in hot climates.

Frequently Asked Questions

How long does a BUR roof last? With proper maintenance, BUR systems commonly last 20 to 30 years, depending on climate and installation quality.

Is BUR good for flat roofs? Yes, BUR is a traditional, durable option for flat or low-slope roofs requiring reliable waterproofing.

What maintenance does a BUR require? Regular inspections, seam resealing, debris removal, and cap sheet protection are typical maintenance tasks.