Knowledge Builders

what is a built up tar and gravel roof

by Oma Bernier Published 5 months ago Updated 3 months ago
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The purpose of gravel on a flat roof

  • Gravel to protect Built-Up Roofs. A built-up roof (BUR), sometimes called a tar-and-gravel roof, is a tried-and-true style of flat roof.
  • Added benefits of BUR flat-roof gravel. Because the gravel holds and releases heat, the layer of gravel on a BUR flat roof can both help water evaporate and keep heat ...
  • Additional benefits of ballast on a flat roof. ...

Built-up roofs or BURs (also called a tar and gravel roof) is a well-established and popular style of flat roof that is made up of alternating layers of roofing felt or fiberglass and asphalt that is applied with heat, which combines to make a long-lasting sturdy roofing system.Jan 2, 2021

Full Answer

What is a tar and gravel roof?

A tar and gravel roof, or built-up roofing, consists of several layers of waterproof material alternated with hot tar and a surface layer of mineral aggregate, often smooth river stone. This surface layer weighs down the built-up roof, protects it from sun exposure, and serves as decoration.

What is a built-up roof?

Built-up roofs or BURs (also called a tar and gravel roof) is a well-established and popular style of flat roof that is made up of alternating layers of roofing felt or fiberglass and asphalt that is applied with heat, which combines to make a long-lasting sturdy roofing system.

Why do contractors use gravel on flat roofs?

Contractors and builders use gravel on flat roofing for two primary reasons; the first is to protect the underlying layer of roofing materials on built-up roofs (BURs), and the second is to secure or weigh down the roofing material, as is the case with single-ply flat roofs. What Are Tar & Gravel Roofs or Built-Up Roofs?

Can you put gravel on a bur flat roof?

Added benefits of BUR flat-roof gravel Because the gravel holds and releases heat, the layer of gravel on a BUR flat roof can both help water evaporate and keep heat away from the underlying roof structure. The gravel provides a better grip for foot traffic when conducting maintenance or repairs.

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What is a tar and gravel roof?

A built-up roof (BUR), sometimes called a tar-and-gravel roof, is a tried-and-true style of flat roof. Here, alternating layers of roofing felt (usually fiberglass) and hot-applied asphalt are combined to create a long-lasting roof system.

How long does a tar and gravel roof last?

25 yearsAsphalt has the ability to waterproof a roof, and extend its lifespan. On average, tar and gravel roofs last for 25 years; with exceptional maintenance, they can last as long as 40 years. This is due to the resilience of the materials, such as the embedded gravel, which resist degradation.

What does built-up mean on a roof?

Built-Up Roofing, or BUR for short, first appeared around the mid 1800's. It is a roofing system where multiple layers of asphalt get applied between ply sheets (or felts) over the roof deck and insulation.

Can you walk on a tar and gravel roof?

Flat Roof Surfaces You Can Walk On Sometimes referred to as tar-and-gravel roofs, BURs are designed with alternating layers of hot tar and waterproofing material. It's then ballasted with a final layer of gravel. Some modern types of BURs, however, use fiberglass membranes as opposed to tar paper.

How do you find a leak in a tar and gravel roof?

A membrane may have visible signs of blisters, cracks, punctures or splitting. The most obvious signs of leaks on a gravel-covered roof are exposed tar in areas where gravel is missing. Tar that is leaking tends to show signs of bubbling or cracking.

How do you fix a leak in a tar and gravel roof?

Apply tar underneath the cut areas and fold cut into the tar. Ensure the coat is applied to the entire area and extends past the repair area. Apply asphalt-saturated fabric to repaired area over the tar, then another layer of tar to the repair area and beyond to the old roof. Push stones over repair area.

How long will a built up roof last?

15 to 30 yearsBuilt-Up Roofing Lifespan Depending on the climate and the specific materials used, built-up roofing has an average life expectancy of 15 to 30 years, but some constructions can last up to 40 years. In general, built-up roofing tends to fare better in warmer climates than in cold regions.

How do you replace a built up roof?

First, with a built up roof construction, contractors lay and fastened base sheets to the subsystem with roofing nails. Next, they use adhesive, asphalt, concrete, or tar, to glue felt over the base sheeting. Last, the final layer roofers install cap sheets or gravel, then topped off with a layer of asphalt.

How thick is built up roofing?

How thick is built-up roofing? A BUR roof system comes in multiple layers, most often between two and four. The thickness depends on the materials used and the number of built-up roofing layers applied, but typically the selvage area ranges between two to four inches.

How long does a flat tar roof last?

15 to 20 yearsThe materials used to make a flat roof play a large part in determining its lifespan. A multi-layer built-up roof consisting of waterproof material, hot tar and gravel can last for 15 to 20 years. Roofs consisting of three to five layers of modified bitumen have a slightly shorter average lifespan of 10 to 15 years.

What is a flat roof with gravel called?

Built-up roofs or BURs (also called a tar and gravel roof) is a well-established and popular style of flat roof that is made up of alternating layers of roofing felt or fiberglass and asphalt that is applied with heat, which combines to make a long-lasting sturdy roofing system.

Are tar and gravel roofs combustible?

A tar and gravel roof is not suitable for a DIY installation, as its installation is potentially very dangerous (under the wrong conditions, hot tar can burst into flames cause severe burns or serious damage to your home).

How long do flat tar roofs last?

A tar and gravel roof will last, on average, anywhere from 20-years to 25-years. That is a fairly standard lifespan for a roof – asphalt roofs, for example, last around 20 years. The exact lifespan of your tar and gravel roof will depend on a few factors.

Should I put gravel on my flat roof?

Gravel flat roofs and pea shingle flat roofs As ballast, the gravel will help anchor the material underneath and lower the risk of it being blown off in high winds. As protection, the stones absorb some of the sun's rays, preventing the roof material from becoming brittle over time.

Why do they put gravel on top of roofs?

Gravel is added on top of tar (and sometimes Single-Ply EPDM) roof systems as protection from UV rays, foot traffic, and wear from weather. If the gravel stones break down, they become less effective and leave your important roof layers prone to wear and damage.

What is the purpose of gravel on a flat roof?

Contractors and builders use gravel on flat roofing for two primary reasons; the first is to protect the underlying layer of roofing materials on built-up roofs (BURs), and the second is to secure or weigh down the roofing material, as is the case with single-ply flat roofs.

What Is A Tar and Gravel Roof?

A tar and gravel roof, or built-up roofing, consists of several layers of waterproof material alternated with hot tar and a surface layer of minera...

Advantages of A Tar and Gravel Roof

Of all the flat roofing options, a tar and gravel roof is the most economical. It provides excellent protection against UV rays and is an attractiv...

Disadvantages of A Tar and Gravel Roof

A tar and gravel roof is very heavy. Joists, or the supports for your roof, may have to be strengthened before application. This kind of roofing is...

What is a tar and gravel roof?

A tar and gravel roof, or built-up roofing, consists of several layers of waterproof material alternated with hot tar and a surface layer of mineral aggregate, often smooth river stone. This surface layer weighs down the built-up roof, protects it from sun exposure, and serves as decoration.

How long does a tar and gravel roof last?

Gravel is an excellent fire retardant. Also, a tar and gravel roof is very rugged and safe to walk on. A tar and gravel roof will generally last around 20 years, although if they are well maintained and properly installed, this kind of roofing has been known to last almost 40 years.

What is a BUR roof?

Tar and gravel roofing , also known as built-up roofing (BUR), has been the go-to flat roof technology for decades. What are the advantages and disadvantages of this type of installation?

Is tar and gravel roof heavy?

A tar and gravel roof is very heavy. Joists, or the supports for your roof, may have to be strengthened before application. This kind of roofing is also very smelly and messy to install, and it is not recommended to install this roof on occupied homes.

Can gravel clog gutters?

Water can travel many feet from the original defect across the different layers of roofing. Gravel can clog gutters and scuppers. A tar and gravel roof is also one of the least green options, and none of the materials are recyclable. For these reasons, many roofing contractors have moved away from tar and gravel roofing to more modern styles such ...

What is a flat roof made of?

Most houses with flat or nearly-flat roofs are topped with built-up roofing, or “tar-and-gravel” roofing, made from fiberglass-based asphalt sheeting that is applied in layers, with hot bitumen (“tar”) mopped on between each layer. The surface is coated with bitumen and a layer of gravel or crushed rock to hold the roofing material down ...

How long does a built up roof last?

The light-colored gravel also reflects the sun’s heat. Built-up roofs can last from 10 to 20 years, depending on the severity of the weather. After a roof is “hot mopped” with asphalt, gravel is spread on top. ©Mikeledray / Shutterstock.com. Built-Up (Tar-and-Gravel) Roofing Diagram © Don Vandervort, HomeTips.

Can a flat roof collect water?

Parts and composition of tar-and-gravel, built-up, and flat roofing systems, with a helpful tar-and-gravel roof construction diagram. Flat or almost-flat roofs can collect a tremendous amount of water, especially if their outlets or downspouts become plugged with leaves and debris.

Is a built up roof a DIY project?

It is generally the least expensive roofing material available. Installing a built -up roof is not a DIY project. If you need a new or replacement built-up roof, contact a licensed built-up roofing contractor in your area.

Do flat roofs seal out standing water?

Ordinary roof shingles won’t seal-out standing water. Ordinary shingles are designed to overlap one another and shed rain downward —this is why they go on sloped roofs. “Flat” roofs (which usually have a very slight slope) utilize a roofing system that is completely sealed and therefore impervious to leaking.

What is a tar and gravel roof?

Traditionally, a tar and gravel roof is usually made of 3 to 5 laminated layers, which are made from asphalt base sheets, hot tar and roofing felt. A top layer of bitumen and extra top mineral coating is also added.

How long does a tar roof last?

Compared to other roofing products, built up roofing is quite inexpensive. However, the lifespan of a tar and gravel roof is only about 10 to 20 years, depending on its installation and the climate. Some well maintained tar and gravel roofs may last up to 25 years.

What type of roof is used for commercial buildings?

Commercial buildings often times have flat roofs, but some modern and historic homes also have roofs with little or no slope. A tar and gravel roof is a type of flat roofing used for some these homes.

Can you refurbish a roof?

Although these refurbishing measures can extend the roof’s lifespan, it should only be done if the roof is still structurally sound. Otherwise, the entire roof will need to be replaced.

Can tar and gravel be used on a flat roof?

Strong sun can also damage the roofing membrane if it is exposed and not covered by the gravel. Tar and gravel roofing is not normally recommended in areas with lots of snow or rain. It is sometimes prone to leaks, especially if the flashing and underlayments are not correctly installed. Flat roofing is prone to ponding, when water stays on a roof surface for more than 48 hours. A tar and gravel roof must have an adequate drainage system to avoid this problem.

What is a Tar & Gravel Roof?

A tar & gravel roof is one of the most common types of metal roofs. It consists of a layer or layers of asphalt saturated felt that are then covered with sand, crushed rock and hot liquid bitumen (tar).

The Benefits of a Tar & Gravel Roof

A tar and gravel roof has many benefits, such as reduced maintenance costs. The lifespan of a tar & gravel is usually 20 – 25 years, depending on location and structure.

Types of Tar & Gravel

There’s more than one way to get your roof looking great! You can choose between two main types of BUR or tar and gravel roofs: modified bitumen, which is a composite mixture with asphalt added in for extra durability.

Applying a Tar & Gravel Roof

When it comes time to install your tar and gravel roof, you need to make sure that the surface is as clean as possible.

Modified Bitumen vs Tar & Gravel

Both roofing systems have their pros and cons, so it’s important that you sit down with a professional beforehand to help figure out what would work best for your needs.

Ballast Tar & Gravel Roofing

Ballast roofing is a great choice for commercial properties that have access to readily available ballast.

Tar & Gravel Roofing Maintenance

Tar and gravel roofs are a long-term investment. The presence of tar in the roofing material gives it strength, while its natural surface helps to prevent leaks from occurring more often than not!

What is tar and gravel roofing?

The reality of “tar and gravel” roofing is that the actual material is slightly more sophisticated than it first sounds.

What are the advantages of tar and gravel roofing?

1. If you’ve got a flat roof that you need covering, tar and gravel is one of the most popular options for good reason. First and foremost – it’s the cheapest.

What type of roof is easy to install?

3. Tar and gravel roofs are also quick and easy to install, and can be administered by most good roofing companies.

How long does a roof last?

Roofs built up with layers of tar and gravel normally last between 10 and 20 years. This can often depend on the sort of external weather conditions they’re ...

What is the purpose of hot bitumen on a roof?

The top layer is then coated with more bitumen and a layer of stone, rock or gravel to hold the other materials down. This also acts as a way of protecting the roof from weather abrasion and other external effects.

Is a flat roof better than a tar and gravel roof?

1. Tar and gravel roofs can be very heavy. One of the benefits of a flat roof is often its lightweight design, but this benefit can be lost with a tar and gravel roof .

Is tar roofing cheap?

7. While tar and gravel roofs might not last quite as long as some other roofing solutions, they are easy and cheap to maintain. If looked after properly, the duration of the roof could be extended considerably.

What is the sealant on a tar and gravel roof?

Another significant variation between the two systems is that on Tar & Gravel roofs, a bitumen chemical sealant goes over the top of the rocks to keep them in place. This sealant can be heat or cold applied.

Why do we need tar on a bur roof?

Because BUR roofs consist of multiple layers of tar, which is water-resistance by itself, topped by a layer of pea-sized ¼" thick gravel, it prevents water from getting beneath the materials to create leaks that can damage your structure.

What is BUR and Its Components?

A BUR roof consists of 3 main components - bitumen material (asphalt), ply sheets (typically 36" wide and referred to as plies), and surfacing materials - one or multiple. These materials go into alternating layers of reinforcing fabric and bitumen.

What is the benefit of a bur roof?

There are many benefits to choosing a BUR roof type for your home. First, BUR roofs have excellent waterproofing. Second, the construction also protects the roof from damage against UV (ultraviolet) rays.

How much does a bur roof weigh?

The final concern about BUR roofs is the heavier weight, which may put too much strain on your roofline. A ballasted roof weighs more, with 10 to 25 pounds per square foot.

How much does it cost to install a bur roof?

A: Installation for a BUR roof using tar & gravel can cost between $3,750 and $6,750. The final cost varies depending on the roof's size, slope, and pitch. For example, one square foot (12" x 12") can cost $2.50 and $4, equaling $250 to $400 a roofing square (100 square feet).

What are the downsides of a bur roof?

The biggest downsides of BUR roofs are the slow installation process, which means high labor costs. Plus, there will be hazardous fumes during the install when using hot bitumen, whereas cold bitumen won't cause harmful fumes.

How big is a gravel roof?

The gravel used is about the size of 0.25″ – 0.5″ inches (0.64 cm -1.27 cm) in diameter . Another key difference is that on Tar & Gravel roofs, the rocks are sealed down using a bitumen-based chemical. The bitumen which seals down the gravel can come in two different forms cold applied and heat applied.

How much does a built up roof cost?

The price for the materials of a Built-Up roof system can cost about $165 to $250 per square. Which can be a pro or a con depending on your budget and if the other pros make it worth the price to you. This price isn’t bad but not great when compared to other roof materials.

How much does a ballasted roof weigh?

A ballasted roof can weight 10 – 25 lbs per square foot. If you decide on a ballasted roof, you will need to ensure your roof structure can support the weight. 5.

What are the two types of roofs?

There are two main types of built-up roof systems the Tar & Gravel system and the Ballasted roof system.

What is a BUR roof?

A built-up roof (BUR) also known as a tar and gravel roof is a popular choice for low slope roof owners.

Why is it so hard to find a leak on a roof?

Leaks can be difficult to find on a built-up roof because there are no seams to check . Roofers will have to remove the gravel to see the tar layer underneath. With ballasted roof systems they will have to dig up several inches to feet of gravel to get to the base layer to spot the hole.

What is PVC made of?

PVC stands for Polyvinyl Chloride and is made up of ethylene and chlorine which are derived from processed petroleum or natural gas and salt respectively. Click Here to Learn More about PVC. Modified Bitumen. Modified Bitumen is a 2-part flat roof system. It was developed in Europe around the 1960s.

What is a tar and gravel roof?

A built-up roof (BUR), sometimes called a tar-and-gravel roof, is a tried-and-true style of flat roof. Here, alternating layers of roofing felt (usually fiberglass) and hot-applied asphalt are combined to create a long-lasting roof system.

Why is gravel used on a ballasted roof?

The gravel in a ballasted roof helps absorb heat, preventing the sun from heating the roof materials below and making the roof more energy-efficient. (Sources: WATERPROOF! Magazine and Roofing Southwest .)

Why is gravel important for a roof?

The weatherproofing layer of gravel gives the roof’s surface a longer life and helps prevent cracking, blistering and degradation, which could lead to leaks or other material failures over time. Even though the asphalt waterproofs the roof (highly important for flat roofs), the gravel provides an important, life-extending extra layer.

What is modified bitumen roof?

Modified bitumen roofs are a mix of asphalt and rubber with a layer of gravel embedded in the top layer of material during manufacture to provide UV protection. No additional gravel on the roof is required. (Source: Roofing Contractors Association of British Columbia .)

Why use ballast on flat roof?

A ballast system helps cut roof system application costs, as it takes less time to install since sealing the layers together isn’t necessary. Ballasted flat roofs are a popular choice, especially for commercial buildings.

What is the purpose of gravel on asphalt?

A layer of gravel, or small stones, is applied on top of the final coating of asphalt to protect the roof from the elements, including ultraviolet (UV) rays and hail. The gravel is embedded into the top coat of asphalt (known as a flood coat), which helps the gravel stay in place. (Source: American Society of Home Inspectors .)

Why is gravel better than other types of gravel?

The gravel provides a better grip for foot traffic when conducting maintenance or repairs.

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