What Is Roofing Tar and How It Works

Roofing tar is a viscous, black sealing compound used to waterproof and protect roofs, flashing, and masonry. This article explains its composition, types, applications, benefits, limitations, safety considerations, and best practices for use in residential and commercial roofing projects. Understanding roofing tar helps homeowners and contractors choose the right material for long-lasting roof protection.

Aspect	Key Points
Composition	Asphalt-based or coal-tar-based binders with solvents and additives
Common Uses	Flashing, patching, roof seams, and underlayment waterproofing
Advantages	Strong adhesion, waterproofing, and affordability
Limitations	UV sensitivity, odor, staining, and not always compatible with some materials
Safety	Ventilation, PPE, and proper disposal required

What Roofing Tar Is Made Of

Roofing tar typically derives from two primary sources: asphalt and coal tar, both of which are byproducts of petroleum or coal processing. Asphalt-based roofing tar contains bitumen, fillers, and solvents that create a thick, sticky material used for sealing and patching.

Coal-tar pitch is made from the distillation of coal and is chemically distinct from asphalt, offering higher resistance to certain chemicals and oils. Coal-tar products emit a strong odor and contain more hazardous PAHs (polycyclic aromatic hydrocarbons) than asphalt-based options.

Modern formulations often add polymers, fibers, and stabilizers to improve flexibility, UV resistance, and adhesion. These additives help the tar perform better in temperature fluctuations and extend service life when used appropriately.

Types Of Roofing Tar And Related Products

There are several roofing tar-related products designed for specific tasks, including cold-applied tars, hot-applied tar, tar emulsion, and roof cement. Each type has distinct handling requirements and application methods tailored to different roofing jobs.

Cold-Applied Tar And Roof Cement

Cold-applied tar or roof cement comes in tubs or cartridges and is applied without heating, making it suitable for small repairs and flashing. It is user-friendly for DIY repairs and reduces the safety risks associated with heating asphalt or coal tar.

Hot-Applied Tar

Hot-applied tar requires heating in kettles and is used for large-scale waterproofing projects or for built-up roofing systems. While offering strong adhesion and effective sealing, hot tar’s application demands professional handling due to burn and fume hazards.

Tar Emulsions

Tar emulsions are water-based mixes where tar droplets are suspended in water and surfactants. They are used for primer coats, roof washes, and environmentally friendlier applications where solvent use is restricted.

Common Uses In Roofing

Roofing tar is used to seal seams, flashings, punctures, and roof penetrations such as vents and chimneys. It creates a waterproof barrier and helps prevent leaks when applied correctly and in compatible scenarios.

Tar is also used in built-up roofing (BUR) systems where multiple layers of felts and hot tar create a durable membrane. In BUR systems, tar acts as the adhesive and waterproofing layer between felts.

For emergency repairs, roofing tar provides a quick, temporary fix to stop active leaks until more permanent repairs can be scheduled. Temporary tar patches should be inspected and replaced or upgraded during regular roof maintenance.

Performance Benefits And Limitations

Roofing tar provides strong adhesion, excellent waterproofing, and affordability compared with some membrane systems. For sealing small areas and creating watertight penetrations, tar remains an effective solution.

However, tar has limitations: it can soften in extreme heat, become brittle with prolonged UV exposure, and sometimes stain roof surfaces. Without protective coatings, tar-based systems often require additional layers or surfacing to enhance UV resistance and longevity.

Compatibility is another concern; certain single-ply membranes and modern roofing coatings are not compatible with coal-tar or asphalt tars. Checking material compatibility prevents chemical reactions that could degrade roofing components.

Health, Safety, And Environmental Considerations

Applying roofing tar involves health and safety risks including burns, inhalation of fumes, and skin irritation. Proper PPE—gloves, goggles, long sleeves, and respirators—is essential for anyone handling tar products.

Ventilation is crucial, especially for hot-applied tar and solvent-based products. Areas should be well-ventilated to minimize fume exposure and reduce the risk of respiratory irritation or long-term health effects.

Environmental considerations include runoff control and disposal. Coal-tar products contain higher levels of hazardous PAHs and may be subject to regulatory restrictions in some municipalities. Contractors should follow local disposal rules and avoid letting tar wash into storm drains.

Best Practices For Applying Roofing Tar

Surface preparation is critical: clean the area of debris, dry the substrate, and remove loose roofing material to ensure good adhesion. Properly prepared surfaces improve bond strength and reduce the likelihood of failure.

For cold-applied tar, use a trowel or caulk gun for consistent coverage and thickness. For hot tar, only trained professionals should heat and apply the material using approved kettles and safety gear. Applying the correct thickness ensures effective waterproofing and prevents premature deterioration.

After application, protect tar from direct sunlight and physical damage. Use surfacing materials, gravel, or protective coatings when appropriate to extend service life. Regular inspection and reapplication of protective layers will prolong performance.

When To Choose Roofing Tar Versus Alternatives

Roofing tar is appropriate for patching, flashing repairs, and use in built-up roofing where compatibility exists. It is a cost-effective choice for targeted repairs and traditional BUR systems.

Alternatives include silicone coatings, elastomeric roof coatings, modified bitumen, and single-ply membranes. These products can offer superior UV resistance, flexibility, or chemical compatibility. Choosing an alternative may be preferable for full-roof restorations or when long-term durability and low maintenance are priorities.

Decision factors should include roof type, climate, exposure to chemicals or oils, desired lifespan, and budget. Consultation with a licensed roofing professional helps match the right material to the project’s needs.

Maintenance, Inspection, And Longevity

Regular inspections identify tar failures early: look for cracks, soft spots, pooling water, and areas where tar has pulled away from seams. Timely maintenance prevents minor issues from becoming major leaks.

Maintenance may include reapplying roof cement, adding flashing, or installing protective surfacing. For built-up roofs, periodic recoatings or gravel replacement restores protection. Planned maintenance schedules significantly extend the functional life of tar-treated roofs.

Typical longevity depends on formulation and exposure; unprotected tar can degrade in a few years while properly protected systems can last a decade or more. Using UV-stabilized coatings and routine care enhances lifespan and performance.

Cost And Availability

Roofing tar products are widely available at hardware stores, roofing supply houses, and online retailers. Prices vary by formulation, packaging, and brand. Cold-applied roof cement and tar caulk are affordable for DIY patching, while hot-applied services cost more due to labor and equipment.

Long-term cost comparisons should factor in maintenance frequency and expected lifespan. A low initial price may require more frequent repairs, increasing lifetime expenses. Investing in higher-quality materials or protective coatings can reduce total cost of ownership for the roof.

Summary And Practical Recommendations

Roofing tar remains a practical material for sealing, flashing, and built-up roofing systems, offering strong adhesion and waterproofing at a reasonable cost. However, its limitations—UV sensitivity, odor, and compatibility issues—make careful selection and proper application essential.

For homeowners and contractors: verify material compatibility, follow safety protocols, prepare surfaces thoroughly, and consider protective coatings for long-term performance. When in doubt, consult a licensed roofer to determine whether tar or an alternative roofing product is the best solution.