Are you setting up your commercial property and are searching for options for your flat roofing system? Then we suggest a tar and gravel roofing system.
As you know the weather in Oklahoma can quickly take a turn for the worse. So naturally, you need a roofing material that holds up well all year long.
So does tar and gravel roofing meet this criteria? Stay with us as we cover all about this unique flat roofing system. We will talk about how it is made, its pros and cons, and how it fares against the top alternatives such as TPO and EPDM.
What Is A Tar and Gravel Roof?
A tar and gravel roofing system is a popular type of flat roofing material made with an alternating combination of bitumen and ply sheets. It is also called a built-up roof because it is made or built up with several layers of material.
Generally, there are three types of materials used: asphalt or bitumen, reinforcing fabric or ply sheets, and surface material like gravel or stones.
This roofing system consists of alternating layers of bitumen and reinforcing materials, topped with a layer of gravel or other aggregate material. The first layer is usually an insulation layer. Over this, one layer of asphalt and one layer of reinforcing fabric. This is done 2-3 times to create a 4-5-ply membrane system. This combination creates a strong, weather-resistant surface that can withstand various environmental conditions.
Also Read: Types Of Roof Membrane For Your Flat Roofs
Understanding The Layers of a Tar and Gravel Roof
Preparation
The existing roof surface is cleaned and prepared for the installation of the new roofing system. This may involve removing old roofing materials and repairing any damage to the roof deck.
Installing The Insulation
After your roof is cleaned and set for installation, it’s time to install the first layer, also known as the base layer. Traditionally the first layer used to be asphalt, but over the years, tar and gravel roofs have seen some changes. Now, insulation acts as the base layer. This adds another layer of protection and boosts the energy efficiency of your roof.
More commonly, insulation is placed above the roof deck but beneath the layers of bitumen and reinforcement. This method is known as “above-deck” insulation and is typical for commercial buildings.
Installing The First Layer (Bitumen/Asphalt)
The first layer of bitumen is applied to the roof deck. This layer is usually composed of hot asphalt or bitumen, which is heated to a liquid state for easy application. This is spread throughout the roof evenly, acting as a waterproof membrane.
There is also another method, known as cold-applied, that uses adhesives that don’t need to be heated to be installed on the roof. Instead of asphalt or bitumen, these roofs use silicone or acrylic-based coatings in between layers of reinforcing fabric. Consulting with a professional roofing contractor can help you decide which system is right for you.
Adding a Reinforcing Layer (Felt/Ply sheet)
Once the bitumen is applied, a reinforcing layer of felt or ply sheet is laid on top. This reinforcing layer serves multiple purposes: it adds strength to the roof, helps distribute the load across the surface, and provides a stable foundation for subsequent layers.
The alternating application of bitumen and reinforcing materials is then repeated several times. Each new layer of bitumen bonds with the previous layers, creating a cohesive, waterproof membrane.
Surface Layer (Tar and Gravel)
Now comes the layer on which the roofing system itself is named. The final step in constructing a built-up roof involves adding a protective top layer, which is crucial for the longevity and performance of the entire roofing system. After the multiple layers of bitumen and reinforcement are in place, a layer of gravel or crushed stone is spread evenly across the roof surface.
The gravel spreader is typically a motorized machine that’s driven across the roof. It has a hopper filled with gravel and a mechanism to distribute it evenly. As it moves, it releases a consistent layer of gravel onto the hot bitumen.
Variations Of Tar and Gravel Roof
While traditional tar and gravel roofs use asphalt or coal tar, there are variations that incorporate other materials, such as modified bitumen. Modified bitumen roofs use a blend of rubber and asphalt, offering increased flexibility and resistance to extreme temperatures.
What Are The Benefits Of Tar and Gravel Roofs?
Tar and gravel roofs offer several advantages, making them a popular choice for both residential and commercial buildings.
Durable and Weather Resistant
Tar and gravel roofs are known for their long lifespan, often lasting 20 to 30 years or more with proper maintenance. The multiple layers of bitumen and reinforcement create a robust, waterproof barrier that helps your roof withstand the harsh conditions in Oklahoma.
The gravel layer on top of the roof provides excellent protection against UV rays, reducing the risk of heat damage and extending the life of the roofing materials. Additionally, the multiple layers of bitumen create a waterproof seal, preventing leaks and water damage.
Fire Resistant
Your tar and gravel roof not only protects your roof from severe weather but fire too. Tar and gravel roofs are inherently fire-resistant due to the non-combustible nature of the materials used in their construction. This makes them a safer choice for buildings in areas prone to wildfires or other fire hazards.
Cost-Effectiveness
Compared to other roofing options, tar and gravel roofs are relatively inexpensive to install and maintain. The materials used in construction are readily available and affordable, making this roofing system a budget-friendly choice.
Energy Efficiency
The insulation properties of the gravel layer help to reduce heat absorption into the building, keeping the interior cooler in hot weather. This can lead to lower energy costs, as less air conditioning is needed to maintain a comfortable indoor temperature.
Limitations Of Tar and Gravel Roofs
While tar and gravel roofs offer many benefits, there are some potential drawbacks to consider before choosing this roofing system for your building.
Weight
One of the biggest concerns building owners have as they decide to install this system is its weight. The multiple layers of bitumen and gravel make these roofs heavy. This may require additional structural support for some buildings, particularly older structures or those with weak roof decks.
Odor
The application of hot asphalt or bitumen during the installation of a tar and gravel roof can emit strong, pungent odors that may linger for a period of time. These odors can be particularly concerning for buildings that are occupied during construction, as they can cause discomfort or respiratory irritation for the occupants. Adequate ventilation and scheduling construction during times when the building is less populated can help mitigate these concerns and make the process more manageable for everyone involved.
Cost Of Tar and Gravel Roofs
As we mentioned above, tar and gravel roofs are quite affordable compared to other flat roofing options.
As per current estimates, tar and gravel roofing costs around $3.50 to $7.50 per square foot. The cost can vary depending on the type of surface layer you choose, the size of your roof, and other factors.
Tar and Gravel vs. Single-Ply Membrane Roofs
Choosing the right roofing system involves understanding the differences between traditional tar and gravel roofs and modern single-ply membrane roofs. Tar and gravel roofs are a type of built-up roof that utilize multiple layers of bitumen and reinforcing materials.
On the other hand, single-ply membrane roofs consist of a single, continuous sheet of synthetic material, such as TPO, PVC, or EPDM. These membranes are lightweight and flexible, making them easier to install.
Both these types of roofing materials tend to be in a similar price range, with tar and gravel roofs being slightly cheaper. Tar and gravel roofs also have a traditional aesthetic appeal and are a good option for schools and industries.
Single-ply membranes are available in different colors and are more durable, but there are concerns when it comes to water resistance.
Also Read: Why Do Commercial Buildings Have Flat Roofs
Upgrade Your Commercial Roof With Our Tar and Gravel Roofs
Tar and gravel roofs, or built-up roofs, offer a durable, cost-effective, and weather-resistant solution for flat or low-slope buildings. With proper maintenance and care, these roofs can provide decades of reliable protection against the elements.
If you want to install a new roof on your commercial building, look no further than the team of A. Fricker Roofing and Waterproofing. We have experts who have the knowledge and skills required to install this intricate roofing system. Contact us at (918) 402-7167 today to schedule a consultation.
