Hot Tar Roofing for Commercial Buildings: What to Expect

Hot tar built-up roofing has protected Atlanta commercial buildings for more than a century, and the smoking kettle parked beside your building is the heart of the whole process. If you manage a flat or low-slope roof, here is what actually happens on installation day and where this proven system fits.

What the Kettle Does on Installation Day

Built-up roofing, often shortened to BUR, is one of the oldest and most dependable systems for flat and low-slope commercial roofs. It is the original "tar and gravel" roof, and you will still find it on warehouses, office buildings, schools, and retail centers across Metro Atlanta. Because the system is built in layers right on the deck, the hot kettle plays a central role. The kettle is a large, insulated tank that melts solid blocks of bitumen, commonly asphalt, into a free-flowing hot liquid. Crews feed it, monitor its temperature carefully, and pump or carry the molten material up to the roof, where it becomes the adhesive and waterproofing that bonds each layer of reinforcing felt. Get the temperature wrong and the bitumen either will not bond properly or breaks down, so an experienced crew watches that kettle like a hawk and logs readings throughout the day. The finished roof is essentially a thick, redundant sandwich, and that redundancy is the whole point: even if one layer is compromised, the others keep water out during Atlanta's heavy summer downpours. On many commercial buildings the assembly also includes rigid insulation and a cover board beneath the plies, which improves energy performance and gives the membrane a stable, fire-resistant base. On site, a professional crew generally moves through these stages:

1. Site setup, positioning the kettle safely away from doors and air intakes, and staging material.
2. Tear-off or prep of the existing roof, depending on whether you are recovering or fully replacing.
3. Heating the bitumen to its target temperature, usually a window of several hundred degrees.
4. Mopping or pumping the hot material and rolling in each ply of felt, layer by layer.
5. Surfacing the roof with gravel or a reflective roof coating to shield it from UV and Atlanta heat.
6. Detailing flashings, drains, and penetrations, then a final walk-through and cleanup.

Strengths, Trade-Offs, and Alternatives

Built-up roofing earns its reputation on durability. A well-built BUR roof can last decades, its multi-ply construction stands up to foot traffic from rooftop equipment service, and its redundant layers give strong protection against ponding and wind-driven rain. The main trade-offs in Georgia are heat and footprint: bare asphalt absorbs heat, so a gravel ballast or reflective coating is important to manage rooftop temperatures, and the kettle, odor, and heavier materials make BUR more involved to install than a single-ply membrane. For that reason, many Atlanta facilities now compare BUR against flame-free single-ply roofing systems such as TPO and EPDM. It is also worth remembering that an existing BUR roof rarely has to be torn off the moment it shows wear; a reflective coating or restoration system can often extend its service life by years while cutting cooling costs through Georgia's hottest months. The right choice depends on your deck, your budget, rooftop traffic, and how long you plan to own the building, and a thorough commercial roof inspection is the best way to weigh those factors honestly.

Whether you are maintaining an existing built-up roof or deciding what should go on your next replacement, the most valuable step is an honest assessment of your current system. If you manage a flat or low-slope building anywhere in Metro Atlanta and want a clear, no-pressure look at your options, reach out to our team and we will help you make a confident, informed decision.