Why Choose A Built-Up Roof? We Break Down The Layers

Built-up roofs, commonly known as BURs, have been trusted roofing solutions for over a century, and for good reason. As one of the most durable and customizable flat roofing options, BURs have stood the test of time thanks to their reliability, longevity, and performance.

But what exactly are BURs and what makes them such a popular choice? We'll break down the composition and benefits of these layered roofing systems to show why they should be on your list when evaluating flat roofing materials.

What Is a Built-Up Roof?

A built-up roof, as the name implies, is a roofing system built up from multiple layered components including:

• Insulation boards
• Alternating layers of bitumen (asphalt) and reinforcing fabric
• A top surface layer of aggregate like gravel or stone

The waterproofing membrane created by the layers of asphalt and fabric provides excellent protection against leaks. The aggregate finish then shields the membrane from weathering and UV radiation while allowing water to easily run off the surface.

Advantages of Built-Up Roofs

Built-up roofs offer numerous advantages that make them a smart choice for many flat roofing projects:

Long Lifespan and Durability

With proper maintenance, BURs can last anywhere from 15-40 years depending on the climate and materials used. The multiple asphalt and fabric layers are resistant to damage and deterioration.

Reliable Waterproofing

The layered composition provides superior leak protection. BURs have proven waterproofing capabilities making them ideal for low-slope commercial roofs.

Weather and Impact Resistance

BURs stand up well to rain, wind, hail, falling debris, and even foot traffic. Their durability makes them suitable for roofs in extreme weather regions.

Other advantages include sustainability, energy efficiency, affordability long-term, and customizability to fit any flat roofing need.

Key Components of a Built-Up Roof

Understanding what each layer in a BUR contributes helps explain why they function so well:

Insulation Layer

Insulation boards like perlite or polyisocyanurate form the base of a BUR system. This provides thermal performance, maintaining comfortable interior temperatures year-round. The type of insulation used depends on climate needs and project budget.

Waterproof Membrane

The core of the roof is the membrane composed of alternating layers of waterproof bitumen and reinforcing fabric, typically fiberglass or polyester mesh. This creates a puncture and tear-resistant barrier preventing leaks from rain and melted snow.

Aggregate Surfacing

The top layer visible on a built-up roof consists of gravel or stones embedded in bitumen. This protective layer shields the membrane from temperature swings, UV rays, hail, and foot traffic. It also reflects sunlight, keeping the roof surface cool, while allowing water runoff.

Installation, Repairs and Maintenance

Proper BUR installation is critical and best left to qualified contractors. The process involves preparing the roof deck, applying hot asphalt, embedding fabric reinforcement, repeating layers, then adding the aggregate top layer. Safety precautions are essential when working with hot asphalt kettles.

Over time, built-up roofs may experience issues like blistering and splitting. Trained professionals can make necessary repairs by cutting out damaged sections, allowing surfaces to dry completely, then using torch applications to re-bond layers.

With routine inspections and preventative maintenance like clearing drains and removing debris, BURs can easily meet and even exceed their expected lifespans.

Recent Innovations in Built-Up Roofs

While built-up roofs utilize proven construction methods, there have also been advances in materials and technology including:

• Use of reflective coatings to improve energy efficiency
• Stronger and sustainable fabric reinforcement options
• Safety enhancements like tie-offs and perimeter warning lines
• Roof analysis using AI and infrared thermography
• Incorporating blue roof designs to control stormwater

These innovations allow BURs to provide better performance while reducing environmental impact.

Built-Up Roofs vs. Other Flat Roof Materials

How do built-up roofs compare to popular flat roofing alternatives like PVC, TPO or EPDM?

While single-ply membranes like TPO and PVC can be quicker to install, built-up roofs exceed their weatherproofing capabilities over the long run. Ballasted EPDM systems match BUR waterproofing but lack durability and customization.

Overall BURs provide better long-term watertightness critical for low-slope roofs. Their layered construction offers increased resilience while options like additional fabric reinforcement allow adapting systems to specific building needs.

When to Choose a Built-Up Roof

Built-up roofs make an excellent choice for:

• Low slope commercial structures
• Roofs in regions with extreme weather
• Buildings requiring hail, fire, wind uplift rating
• Surfaces allowing heavy foot traffic
• Unique roof shapes and custom specifications

Talk to a qualified contractor about whether a built-up roof is right for your flat roofing project and climate conditions.

Built-up roofs have a higher upfront installation cost, averaging $3-$8 per square foot. This includes extensive labor and hot asphalt. However over their lifespan, properly maintained BURs provide excellent return on investment.

Many roofers offer 10-20 year warranties on materials and workmanship. With proper care, built-up roofs typically last 25-30 years on average. Some may remain watertight for 40+ years with preventative maintenance.

For critical commercial structures where leaks are unacceptable, built-up roofs deliver the time-tested waterproofing and customization needed. Contact a professional roofer to determine if a layered BUR system makes sense for your next project.