If you’re responsible for a commercial property with a tar and gravel commercial roof, you’ve probably asked: Is this really the best roofing system for my building today? You’re not alone. At Weather Shield Roofing Systems, we’ve been helping businesses upgrade and maintain commercial roofing systems for over 40 years, and we’ve seen firsthand how tar and gravel—also known as built-up roofing—can create more problems than solutions for today’s property owners. 

Tar and gravel roofs were once a popular choice for flat commercial buildings. But roofing materials and performance expectations have evolved. If your building still has this older system in place, it’s worth understanding the risks, maintenance challenges, and modern alternatives that could save you money and stress long-term. 

Why Are Tar and Gravel Roofs So Heavy?

One of the most common concerns with tar and gravel commercial roofs is their weight. These systems typically add 5 to 10 pounds per square foot to your roof structure. That may not sound like much, but across a 20,000-square-foot roof, that’s 100,000 to 200,000 extra pounds your building is carrying. 

Over time, this extra weight can lead to: 

• Structural strain on the roof deck 

• Sagging or deflection of support beams 

• The need for expensive reinforcements or retrofits 

If your building is older or wasn’t designed for that kind of load, this becomes a serious concern. Lighter commercial roofing systems, like TPO, offer strong protection without stressing your structure. 

Why Are Built-Up Roofs Hard to Inspect?

Another major issue with tar and gravel commercial roofs is how difficult they are to inspect. The gravel layer that protects the waterproof membrane also hides it from view. That means roofing professionals often have to move gravel by hand to check for damage. 

When leaks, cracks, or blisters hide under gravel, they can go undetected for years—until water starts making its way into the building. By the time it shows up inside, the damage (and repair cost) is already significant. 

Compare this to single-ply roofing systems like TPO, PVC, or EPDM, where the membrane is exposed and inspections are quick and accurate. Our Max Life™ Roof Care program makes early detection even easier, helping commercial property owners extend the life of their roofing investment through proactive maintenance. 

Can the Gravel Itself Cause Roof Damage?

Yes, and it often surprises building owners. While gravel is intended to protect the membrane from UV damage and foot traffic, it doesn’t stay smooth forever. Over time, wind, sun, rain, and rooftop traffic break down the stones into sharp fragments.

These fragments can actually puncture or wear down the membrane, defeating the purpose of the gravel layer. Even basic maintenance visits—like HVAC service—can shift the gravel, leaving some spots exposed and vulnerable to damage. 

This adds risk every time someone walks the roof. 

What Problems Does Standing Water Create?

Flat roofs are always at risk of ponding water, but tar and gravel systems make the issue worse. Gravel traps moisture, especially in low areas. Instead of evaporating quickly, small pools of water linger for days, breaking down the roof membrane over time. 

Standing water on a tar and gravel roof can lead to: 

• Membrane deterioration 

• Mold or mildew growth 

• Waterlogged insulation 

• Voided manufacturer warranties 

Modern single-ply roofing systems are smoother, allowing water to drain or evaporate more efficiently—reducing long-term risks and keeping your building dry and healthy. 

What Are the Better Roofing Alternatives Today?

If you’re dealing with repeated repairs or structural concerns from your tar and gravel roof, you’re probably wondering: Is there a better way? 

The answer is yes. Today’s most popular commercial roofing systems include TPO, PVC, and EPDM membranes. These single-ply roofing systems offer several clear advantages: 

• Lightweight: Easier on your building’s structure 

• Fully exposed membrane: Makes inspections and repairs faster 

• Durable and flexible: Adapts to building movement and weather 

• Energy-efficient: Especially TPO, which reflects UV rays and reduces cooling costs 

These systems are designed with modern commercial properties in mind—balancing performance, cost-efficiency, and ease of maintenance. 

How Do I Know If It’s Time to Replace My Tar and Gravel Roof?

Here are some red flags that it’s time to assess or replace your built-up roofing system: 

• Persistent leaks, even after multiple repairs 

• Soft, spongy spots when walking the roof 

• Noticeable ponding or water damage 

• Sagging roof deck or structural issues 

• Escalating energy bills due to poor insulation 

If you’re seeing one or more of these signs, it’s time to schedule a professional roof inspection. At Weather Shield Roofing Systems, we’ll evaluate your current roof, document any problem areas with photos, and explain your options in simple, clear terms. 

We know commercial roofing is a major investment. That’s why our recommendations always focus on long-term value, roof cost savings, and minimizing disruption to your business. 

If you’re managing a building with a tar and gravel commercial roof, it’s smart to understand your risks and your options. The good news is: you’re not stuck with an outdated system. At Weather Shield Roofing Systems, we’re here to help you make confident, cost-effective decisions that protect your property and your bottom line. 

Let’s figure out what’s next for your roof—schedule your free commercial roof inspection today! 

Related Blog Posts: 

What is TPO Roofing? 

Is Single-Ply Membrane Roofing the Right Choice for Your Commercial Building? 

How Much Does Single-Ply Commercial Roofing Cost in 2025? 

Is it Bad to Have Water on My Roof?