Commercial Asphalt Roof

Commercial Asphalt Roof – Of course. A commercial asphalt roof is a common and cost-effective system for large buildings, but it has specific characteristics and maintenance needs that differ from residential roofs.

This guide will cover the types, components, common issues, and repair strategies for commercial asphalt roofs.

What is a Commercial Asphalt Roof?

Typically, this refers to a Built-Up Roof (BUR) or Modified Bitumen (Mod Bit) system. These are multi-layered, durable assemblies designed for large, low-slope (“flat”) roofs.

• Built-Up Roof (BUR): The classic “tar and gravel” roof. It consists of multiple layers (plies) of asphalt-saturated roofing felts alternated with layers of bitumen (asphalt or coal tar pitch), topped with a protective layer of aggregate (gravel or slag) or a mineral surface cap sheet.

• Modified Bitumen (Mod Bit): A more modern version using factory-manufactured rolls of asphalt that has been “modified” with plastic or rubber polymers (like APP or SBS) for increased flexibility, strength, and ease of installation. It is often installed in two layers.

Key Components & Terminology

1. Deck: The structural base (e.g., steel, concrete, or wood).

2. Vapor Retarder: (Optional) A layer to prevent moisture from inside the building from migrating into the roof assembly.

3. Insulation: Rigid boards (e.g., polyiso, EPS) placed on top of the deck for energy efficiency.

4. Base Ply / Felts: The reinforcing fabric layers that form the core of the BUR system.

5. Bitumen: The waterproofing adhesive. Either hot asphalt, cold-applied adhesive, or mastic.

6. Flashing: Sheet metal (or membrane) used to waterproof seams at walls, parapets, drains, and vents.

7. Surface: The top layer, which is either:

   • Aggregate (Gravel): Protects the underlying layers from UV rays and physical damage.

   • Cap Sheet: A mineral-surfaced roll that is embedded in the top layer of bitumen.

   • Reflective Coating: A white or elastomeric coating applied over the surface for UV protection and energy savings.

Common Problems & How to Identify Them

Commercial asphalt roofs are robust but face several common issues:

1. Leaks and Moisture Infiltration:

   • Cause: The #1 problem. Often due to failed flashing, cracks in the membrane, or open seams.

   • Identification: Interior water stains, mold, or drips. On the roof, look for punctures, splits, or deteriorated flashing.

2. Blistering:

   • Cause: Trapped moisture or air between the plies of felts or under the membrane heats up and expands.

   • Identification: Bubbles or raised areas on the roof surface. Do NOT puncture them unless they are already cracked, as this can create a leak.

3. Alligatoring:

   • Cause: Aging and long-term exposure to UV rays and weather, which causes the bitumen to dry out and lose its oils.

   • Identification: A pattern of cracks that resembles alligator skin. This is a sign that the roof is nearing the end of its service life and may need a restoration or replacement.

4. Ponding Water:

   • Cause: Insufficient slope or sagging in the deck, preventing water from draining to scuppers or drains within 48 hours.

   • Identification: Standing water on the roof more than two days after rainfall. This accelerates wear and leads to premature failure.

5. Flashing Failures:

   • Cause: Thermal expansion/contraction, poor installation, or deterioration of sealant.

   • Identification: Cracks, rust, or separation where the roof meets a wall, parapet, or penetration (pipes, vents).

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Repair & Maintenance Strategies

The right approach depends on the roof’s condition, age, and budget.

A) Routine Maintenance & Minor Repairs

• Keep it Clean: Regularly clear debris (leaves, branches) and ensure drains, scuppers, and gutters are not clogged.

• Minor Patching: For small punctures or cracks in a Mod Bit or smooth-surface BUR roof, a mastic or asphalt cement patch can be applied, often reinforced with fabric.

• Flashing Repairs: Re-sealing the counterflashing with a high-quality urethane or silicone sealant can address minor leaks.

B) Professional Restoration & Major Repairs

This is where a professional roofing contractor is essential.

1. Roof Coatings (Restoration):

   • What it is: A fluid-applied layer, typically acrylic, silicone, or urethane, that is rolled or sprayed over the entire roof surface.

   • Best for: Roofs with alligatoring or widespread surface deterioration but a sound underlying structure.

   • Benefits: Seals the surface, restores waterproofing, provides UV protection, and can be highly reflective (saving on energy costs). This is often the most cost-effective alternative to a full replacement.

2. Hot Mop / Torch-Down Patching:

   • For BUR or Mod Bit systems, professionals can cut out the damaged section and install a new, integrated patch using hot asphalt (mop) or a propane torch (for APP-modified bitumen). This creates a seamless, welded repair.

3. Re-covering:

   • If the existing roof is structurally sound, a new Mod Bit or single-ply membrane can sometimes be installed directly over the old one. This avoids the cost and mess of a tear-off.

4. Complete Tear-Off and Replacement:

   • The most extensive and expensive option. The old roof system is completely removed down to the deck, which is inspected and repaired. A brand-new roofing system is then installed. This is the only way to address a compromised deck or saturated insulation.

When to Call a Professional Roofer

For any commercial property, engaging a professional is almost always the rule. Call one for:

• Any active leak.

• Widespread alligatoring, blistering, or cracking.

• Significant ponding water.

• Roofing warranty compliance (many warranties require professional maintenance and repairs).

• Safety and liability: Working on a commercial roof involves significant fall risk and requires proper safety equipment and insurance.

Cost Considerations

Commercial roofing is priced by the square (100 sq. ft.) or per square foot.

• Minor Repair: $500 – $2,000

• Roof Coating / Restoration System: $1.50 – $4.00+ per sq. ft.

• Re-cover: $4.00 – $8.00 per sq. ft.

• Complete Replacement: $8.00 – $15.00+ per sq. ft.

Continuing the Conversation: The Roof Lifecycle & Long-Term Strategy

A commercial roof is a long-term asset. Thinking beyond individual repairs to a holistic management strategy is key.

A) The Three Key Phases of a Commercial Roof:

1. Preventive Maintenance & Minor Repairs (Years 1-10):

   • Goal: Maximize the roof’s designed service life.

   • Actions: Biannual inspections (spring and fall), keeping drains clear, promptly addressing small punctures or open seams, and maintaining flashing seals. This is the most cost-effective phase.

2. Major Repairs & Restoration (Years 10-20+):

   • Goal: Delay the massive capital expense of a full replacement.

   • Actions: This is where roof coatings and overlays come in. A restoration system can add 10-15 years of life to a tired but structurally sound roof. It addresses widespread surface wear like alligatoring and ponding water issues with tapered insulation.

3. Replacement & Capital Planning (Year 20+):

   • Goal: Install a new, reliable, and warrantied roof system.

   • Actions: A full tear-off and replacement is a major capital project. It’s the time to reassess insulation R-values, explore different roofing systems (e.g., switching from BUR to TPO), and plan for future rooftop equipment.

B) The Critical Role of a Roof Asset Manager:
For a portfolio of buildings, treating the roof as a financial asset is crucial. This involves:

• Maintenance Logs: Documenting every inspection and repair.

• Lifecycle Cost Analysis: Comparing the long-term cost of restoration vs. replacement.

• Budget Forecasting: Planning for the major expense of replacement years in advance.

Exploring a Specific Topic: Roof Coatings in Detail

Since coatings are a critical restoration tool for aging asphalt roofs, let’s focus there.

How Coatings Save an Aging Asphalt Roof:

1. Waterproofing: They form a seamless, monolithic membrane over the entire surface, sealing all the small cracks, alligatoring, and minor imperfections.

2. UV Protection: The sun’s ultraviolet rays are the primary cause of asphalt drying out and cracking. Coatings block these rays, drastically slowing the aging process.

3. Reflectivity: Most coatings are white or reflective, reducing the roof surface temperature by 50-80°F. This lowers cooling costs and reduces thermal expansion/contraction stress on the roof.

Types of Coatings for Asphalt Roofs:

• Acrylic (Water-Based): Most common and cost-effective. Highly reflective and elastic. Best for climates with plenty of sun and rain to wash off dirt.

• Silicone: The king of waterproofing. Stays flexible and ponds water exceptionally well. It is softer and can attract dirt, slightly reducing reflectivity over time.

• Polyurethane/Urethane: Extremely tough and abrasion-resistant. Often used as a top coat over a silicone or asphalt primer for roofs that receive foot traffic.

Next Steps and Actionable Advice

What would you like to do next?

• “Tell me more about [Specific Topic]”: Such as roof coatings, how to choose a contractor, dealing with ponding water, or the difference between APP and SBS modified bitumen.

• “I have a specific problem”: Describe the issue (e.g., “I have alligatoring over 60% of my roof and a leak near a drain”), and we can discuss a more targeted strategy.

• “Compare two systems”: We can do a deeper dive into the pros and cons of, for example, a TPO replacement vs. a silicone coating restoration for an old BUR roof.

The world of commercial roofing is vast. Let me know which direction you’d like to go, and we can continue the conversation from there.