# Roofing Kettle

> A fuel-fired tank that melts and heats asphalt or coal tar for hot-applied built-up roofing and other hot-mopped systems.

- URL: https://roof.wiki/roofing-kettle/
- Topic: Tools & Equipment
- Also known as: tar kettle; asphalt kettle; bitumen boiler
- Regions: Global, North America
- First published: 2026-11-02 · Last reviewed: 2026-11-02
- Cite as: "Roofing Kettle." roof.wiki. https://roof.wiki/roofing-kettle/

## Key facts

- **Used for:** Hot-applied built-up roofing and mopped systems
- **Max asphalt temperature:** 550 °F (288 °C)
- **Minimum flash point:** 500 °F (260 °C), ASTM D312

A roofing kettle is a heated vessel used to melt solid asphalt (or, historically and in some markets, coal tar pitch) and keep it at the correct temperature for application. Kettles are central to hot-applied built-up roofing (BUR), where layers of felt are bonded with mopped or mechanically spread hot bitumen, and to some modified bitumen and waterproofing work.

## Equipment

- **Kettles or tankers**, typically trailer-mounted, heated by propane or other fuel burners, with capacities sized to the job.
- **Thermometers and thermostatic controls** to monitor and limit temperature.
- **Pumps and pipelines** to move hot bitumen to the roof, or **luggers** and buckets for hand transport.
- **Lids and lid-closing mechanisms** to smother fires and reduce fumes.
- **Mops and mechanical spreaders** for application.

## Temperature control

Correct temperature is essential to roof performance and safety. Industry guidance uses the **equiviscous temperature (EVT)**, the temperature at which the bitumen reaches the viscosity suited to mopping or mechanical spreading, measured at the point of application. Guidance published through IIBEC includes:

- Asphalt has a minimum flash point of 500 °F (260 °C) under ASTM D312.
- Asphalt should not be heated above 550 °F (288 °C), nor within 25 °F (14 °C) of its flash point.
- Asphalt should not be held between 500 °F and 550 °F for more than about four hours.
- Kettles are typically run somewhat above EVT to allow for heat loss in transport.

Overheating can lower the asphalt's softening point ("drop-back"), changing its properties.

## Hazards

- **Burns** from hot bitumen are a serious risk; workers wear long sleeves, gloves, boots and eye protection.
- **Fire**: kettles must be attended, placed away from buildings and combustibles, with extinguishers nearby.
- **Fumes**: US NIOSH has studied asphalt fume exposure among roofers; controls include keeping lids closed and avoiding excessive temperatures.
- **Propane** cylinders and lines must be handled safely.

Many jurisdictions regulate kettle placement, attendance and fuel storage through fire codes. The use of hot-applied systems has declined in some markets as cold-applied, self-adhered and single-ply systems have grown.

## Sources

1. EVT: Equiviscous Temperature in Built-Up Roofing — IIBEC. https://iibec.org/publication-post/evt-equiviscous-temperature-in-built-up-roofing/
2. Controlling kettle and maintaining the temperature of hot asphalt in cold weather commercial roof applications — RoofersCoffeeShop. https://www.rooferscoffeeshop.com/post/controlling-kettle-and-maintaining-the-temperature-of-hot-asphalt-in-cold-weather-commercial-roof-applications
3. Asphalt Fume Exposures During the Application of Hot Asphalt to Roofs (archived) — NIOSH. https://webarchive.library.unt.edu/eot2008/20090114025144/http:/www.cdc.gov/niosh/docs/2003-112/2003-112p2.html