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A Tar and Gravel Roof Guide for Beginners

Date: August 20, 2023

One of the most traditional and time-tested methods of roof construction is the tar and gravel roof, also known as a built-up roof (BUR). While less common in residential properties, these types of roofs are commonly found in commercial buildings due to their durability, cost-effectiveness, and ease of maintenance. 

Whether you're contemplating a new roof, seeking to better understand your existing roof, or simply curious, this tar and gravel roof guide is a foundation for exploring this durable roofing option. This aims to provide a comprehensive overview of this roofing type, its construction, pros and cons, and factors to consider when deciding if it's the right fit for your building.

What is a Tar and Gravel Roof?

A tar and gravel roof is a type of built-up roof that consists of multiple layers of waterproof materials alternated with hot tar and topped with a layer of gravel. This form of roof construction has been around for over a century, largely due to its proven durability and resilience against harsh weather conditions.

The tar and gravel act as a strong barrier against water penetration, while the gravel protects the layers beneath from sunlight and physical damage. This makes tar and gravel roofs highly resistant to leaks, unlike some other roofing types.

Construction of a Tar and Gravel Roof

A model showing tar and gravel roof layers for tar and gravel roof guide

The construction of a tar and gravel roof is a multi-step process that involves the installation of several layers of materials. Here's a step-by-step guide on how a tar and gravel roof is constructed:

  1. Preparing the Roof Deck: The first step is to prepare the roof deck by applying the built-up roofing materials. This might involve repairing any damaged areas of the existing roof or, in the case of new construction, ensuring the deck is clean, dry, and free from debris.
  2. Installing the Base Layer: A base layer is installed directly onto the roof deck. This is usually an asphalt-impregnated roofing felt or fiberglass mat. The base layer acts as a secondary barrier against water penetration and provides a smooth, even surface for the subsequent layers.
  3. Applying the Hot Tar: Hot tar is applied once the base layer is in place. The tar is heated to a liquid state and spread evenly over the base layer. This hot tar acts as a waterproofing agent and an adhesive for the next layer of roofing felt.
  4. Adding the Roofing Felt: Following the hot tar, a layer of roofing felt is installed. The roofing felt is saturated in asphalt to make it water-resistant. This layering process of hot tar and roofing felt is repeated several times. Usually, three to five layers are added to create a highly durable and waterproof barrier.
  5. Applying the Final Layer of Tar: A final layer of hot tar is applied over the last layer of roofing felt. This prepares the surface for the application of the gravel.
  6. Spreading the Gravel: The final step is to spread a layer of gravel or crushed stone over the tar. The gravel serves multiple purposes: it protects the underlying layers of tar from ultraviolet (UV) radiation from the sun, which can break down the tar over time; it provides a layer of fire resistance; and it adds ballast to the roof, which can help prevent wind damage.

While this process is relatively straightforward, it does require the proper equipment and expertise to perform correctly. The installation process is often messy and potentially hazardous due to the hot tar, so it's recommended that it be carried out by a professional roofing contractor. The longevity and performance of a tar and gravel roof are highly dependent on the quality of its installation.

Remember, while tar and gravel roofing has a long lifespan, it still requires regular maintenance and inspection to ensure it stays in good condition. Debris should be removed, and any areas of exposed tar or damaged gravel should be repaired promptly to prevent leaks.

Advantages of Tar and Gravel Roofing

infographic illustrating the advantages and disadvantages of tar and gravel roofing

Tar and gravel roofs, also known as built-up roofs, have been used for over a century due to their inherent benefits. Let's delve into some of the advantages of tar and gravel roofing:


Tar and gravel roofs are known for their durability. When correctly installed and maintained, these roofs can last up to 30 years or even longer in some cases. The multiple layers of tar and felt create a resilient barrier against the elements, ensuring a long lifespan.

Weather Resistance

These roofs stand up exceptionally well to various weather conditions. They are highly resistant to leaks and can handle the rigors of both hot and cold climates. The gravel top layer serves as an excellent protectant against sun damage, heavy rains, and wind.

Low Maintenance

Tar and gravel roofs require relatively low maintenance compared to other roofing types. Routine inspections and prompt repair of any minor issues are usually sufficient to keep these roofs in good condition. The gravel top layer also protects the lower layers, reducing the frequency of repairs.


These roofs are often more affordable than other commercial roofing options, both in terms of initial installation and long-term maintenance costs. This is especially true when the longevity of tar and gravel roofs is considered.

Fire Resistance

The gravel layer of a tar and gravel roof provides excellent fire resistance, potentially slowing the spread of flames in case of a fire.

Sound Insulation

Gravel roofs are excellent at soundproofing. The tar, roofing felt, and gravel layers work together to minimize noise from rain, wind, or hail, making it a quiet option.


Tar and gravel roofs can be installed on various building types and roof designs. They're suitable for both flat roofs and those with a slight slope.

These advantages make tar and gravel roofing a popular choice for many commercial buildings and some residential properties, especially in areas that experience varying weather conditions throughout the year.

Disadvantages of Tar and Gravel Roofing

3d model showing tar and gravel roof layers for tar and gravel roof guide for beginners

While tar and gravel roofs come with many advantages, they also have certain downsides that need to be considered. Here are some potential disadvantages of tar and gravel roofing:


One of the most significant drawbacks of tar and gravel roofs is their weight. The multiple layers of tar, roofing felt, and gravel make this roofing type heavier than others. Buildings must have the structural integrity to support this weight, which may be impossible for some older structures or certain designs without additional reinforcement.

Installation and Repair Complexity

The tar and gravel roof installation process is more complex and time-consuming than some other types of roofing. It involves handling hot tar and multiple layers, which can be messy and require specialized skills. Similarly, locating and repairing leaks can be difficult and require professional intervention.

Heat Absorption

Tar and gravel roofs can absorb a lot of heat, particularly if the gravel is a darker color. This can make buildings hotter during the summer months and increase cooling costs. They are not as energy-efficient as other roofing types, like cool roofs or green roofs, that reflect more sunlight and provide better insulation.

Limited Aesthetic Appeal

Compared to other roofing options, tar, and gravel roofs might be seen as less aesthetically pleasing. They don't offer the variety of colors and styles that options like shingles or metal roofing provide.

Potential for Foot Traffic Damage

If the roof is accessed frequently for HVAC maintenance or other reasons, the protective gravel can be inadvertently kicked away, exposing the underlying layers to damage.

Poor Drainage

In the case of flat or nearly flat roofs, improper installation can lead to poor drainage, pooling, or standing water. This could eventually lead to leaks or shorten the lifespan of the roof.

Considering these factors is crucial when deciding whether a tar and gravel roof is the right choice for your building. Consulting with a professional roofing contractor who can assess your circumstances is always recommended.

Is a Tar and Gravel Roof Right for Your Building?

An image showing a tar and gravel roof
A tar and gravel roof

Choosing a tar and gravel roof hinges on several factors, including your building's structure, geographical location, purpose, and budgetary constraints. Due to their weight, tar and gravel roofs require a building with adequate structural strength. Weather conditions also matter, as these roofs are durable but can absorb heat, possibly raising indoor temperatures in hot climates.

The use of your building is another factor. If your roof requires regular maintenance access, a tar and gravel roof can be beneficial due to its resilience to foot traffic, although care is needed to avoid gravel displacement.

In terms of cost, tar and gravel roofs can be more economical than other types, both initially and in the long term, and they can last up to 30 years or more if well-maintained. However, if energy efficiency is a priority, other more insulating roofing options might be preferable. A professional roofing contractor can provide tailored advice and ensure proper roof installation.


Tar and gravel roofs are versatile and cost-effective options known for their durability and weather resilience. However, it's important to consider the structure of your building, as these roofs are heavy and require a solid foundation. Their installation and repair can also be complex and requires professional expertise.

While tar and gravel roofs are long-lasting and require low maintenance, they can absorb more heat compared to other roofing types and may not be the most aesthetically appealing option. Care should be taken if your roof requires regular access and, despite their benefits, they might not be as energy-efficient as some modern alternatives.

Professional guidance is crucial when deciding on a tar and gravel roof. With the information provided in this guide, you can decide on the best roofing solution for your building, considering your specific requirements and budget. Remember, your roof is a significant investment, and choosing the right one can contribute to the longevity and value of your property.

Tar and gravel roof replacement

About Mikku & Sons
Mikku and Sons red repair track with its logo painted on its side- roofing company track wraps
Our roofing company was founded in 2001 by Michael Riutta, who is still part of the ownership and management team. Between Michael, his two sons and co-owners, Devin and Joshua, and our crew members, we have many years of experience to handle any type of roof repair or roof installation solutions you may need.