The objective of gravel on a level roof

On many flat-roof (low-slope) commercial structures, it’s common to view gravel on height of the roof. Have you ever before wondered why home builders install gravel on flat roofs?

Gravel is used on level roofs for two reasons:

To protect the underlying layer of roofing materials, as is the situation with built-up roofs (BURs).To weigh dvery own or secure the roofing product, as is the instance via single-ply level roofs.

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There are various forms and weights of gravel used on level roofs for these functions.

Gravel to safeguard Built-Up Roofs

A built-up roof (BUR), periodically dubbed a tar-and-gravel roof, is a tried-and-true style of level roof. Here, alternating layers of roofing felt (usually fiberglass) and also hot-applied asphalt are unified to develop a long-lasting roof mechanism.

A layer of gravel, or little stones, is used on optimal of the final coating of asphalt to defend the roof from the facets, consisting of ultraviolet (UV) rays and hail. The gravel is embedded right into the peak coat of asphalt (recognized as a flood coat), which helps the gravel stay in location. (Source: Amerihave the right to Society of Home Inspectors.)


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The weatherproofing layer of gravel gives the roof’s surchallenge a longer life and also helps prevent cracking, blistering and degradation, which could bring about leaks or various other material failures over time.

Even though the asphalt waterproofs the roof (very vital for level roofs), the gravel provides a vital, life-extending additional layer. Although typically dubbed “gravel,” the height layer is commonly some sort of accumulation product (such as pea gravel, slag or mineral granules). (Source: Everybody Needs a Roof.)

BUR accumulation is normally pea-sized, around a quarter-inch thick, and also is offered to imcomponent the Class A surchallenge burning desigcountry in accordance via mandatory needs for ASTM E108, UL790 or CAN/ULC S107M. (Sources: Absolute Roof Solutions, WATERPROOF! Magazine.)


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Added benefits of BUR flat-roof gravel

Because the gravel holds and releases heat, the layer of gravel on a BUR flat roof deserve to both assist water evaporate and store heat ameans from the underlying roof framework.The gravel offers a better grip for foot web traffic when conducting maintenance or repairs.

Modified bitumales roofs are a mix of asphalt and also rubber through a layer of gravel installed in the height layer of material in the time of manufacture to provide UV security. No additional gravel on the roof is compelled. (Source: Roofing Contractors Association of British Columbia.)

Gravel on a ballast roof system

Ballast is a different style of gravel, which is used to single-ply roofing systems. Although the primary purpose of ballast is to weigh dvery own the roofing materials, it additionally supplies similar protective benefits as defined above.

Ballast is frequently offered through roofs made of tar-and-gravel roof options, including ethylene propylene diene monomer (EPDM), polyvinyl chloride (PVC) and also thermoplastic polyolefin (TPO) single-ply flat roofs.


Single-ply roofing products aren’t self-adhered, nor are they sealed together in any means. Due to the fact that nopoint secures the waterproofing membrane to the roofing products underneath, ballast is required for weight to safeguard the roof from solid winds.

Ballast is various from BUR protective gravel. Ballast stones are normally one to two inches thick and used more generously than on a built-up roof. The heavier stones provide comprehensive security versus wind gusts. (Source: Roofing Southwest.)

A ballast system helps cut roof system application prices, as it takes less time to install considering that sealing the layers together isn’t important. Ballasted flat roofs are a popular alternative, particularly for commercial structures.

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More benefits of ballast on a level roof

Although single-ply roofs naturally have sun-protective features, ballast provides an extra layer of protection from UV rays.Ballast also protects versus hail and from foot web traffic during repair or maintenance work-related.