Roofing Tar vs Silicone: Choosing the Best Roof Coating

Roofing decisions often come down to material performance, cost, and longevity. This article compares roofing tar vs silicone to help homeowners and property managers weigh durability, application, maintenance, and value for flat and low-slope roofs across the United States.

Feature	Roofing Tar	Silicone
Primary Use	Patch/adhesive, built-up roofs	Coating/sealant for flat roofs
Water Resistance	Good Initially, Prone To Cracking	Excellent, Long-Lasting
UV Resistance	Poor	Excellent
Maintenance	Frequent Repairs	Low Maintenance
Typical Lifespan	5–15 Years	10–25+ Years

How Roofing Tar And Silicone Work

Roofing tar is a viscous hydrocarbon product used as a waterproofing layer, adhesive, or patching compound often applied hot or cold on built-up roofs and flashing.

Silicone roof coatings are silicone polymers applied as a liquid that cures to form a seamless, highly elastic, UV-stable membrane suitable for ponding water and reflective coatings.

Material Composition And Properties

Tar typically includes coal tar or asphalt compounds mixed with fillers; it is thick, sticky, and becomes brittle with age and UV exposure.

Silicone is a synthetic polymer based on polysiloxane chemistry; it remains flexible across wide temperatures, resists UV degradation, and repels water effectively.

Performance: Waterproofing And Ponding Water

Silicone excels at ponding water situations because it does not degrade when exposed to standing water and maintains elasticity to bridge gaps and seams.

Roofing tar can be water-resistant initially, but prolonged ponding often accelerates cracking, shrinking, or adhesion loss, leading to leaks.

UV, Weather, And Temperature Resistance

Silicone offers superior UV stability and resists oxidation, so it preserves tensile strength and flexibility under sun exposure and temperature cycling.

Tar degrades faster in sunlight, becoming brittle, chalking, and susceptible to thermal cycling damage in climates with wide temperature swings.

Longevity And Lifecycle Costs

Silicone coatings typically last 10–25+ years depending on system, thickness, and substrate preparation; long service life often offsets higher initial costs.

Tar-based systems often need more frequent maintenance, with lifespans commonly between 5 and 15 years depending on climate and installation quality.

Application And Installation Considerations

Silicone requires careful surface prep — cleaning, dry substrate, and priming in some cases; it is applied by roller, brush, or spray and cures by moisture exposure.

Tar can be applied hot or cold; hot application needs specialized equipment and safety measures, while cold-applied products are easier but may not bond as well.

Adhesion And Compatibility With Roof Types

Silicone adheres well to many substrates including metal, single-ply membranes, and concrete, but adhesion can be reduced on dirty or oily surfaces; primers improve bonding.

Tar bonds strongly to asphalt-based materials and wood, but compatibility with modern single-ply membranes (like TPO or PVC) is limited and may require specific adhesives.

Maintenance, Repairs, And Recoating

Silicone systems are low maintenance; repairs are usually simple patch coatings and periodic inspections, with recoating possible after many years depending on wear.

Tar systems demand more frequent patching for cracked or split areas; cumulative repairs can add cost and reduce long-term watertightness.

Cost Comparison And Value Analysis

Initial cost per square foot for silicone is generally higher than basic tar products, but long-term value often favors silicone due to fewer repairs and longer life.

Tar appears cheaper upfront, but reactive maintenance, shorter lifespan, and potential re-roofing can raise total lifecycle costs above silicone in many scenarios.

Environmental Impact And Reflectivity

Silicone coatings can be formulated as highly reflective — reducing roof surface temperatures and lowering cooling loads, which improves energy efficiency and urban heat island impacts.

Tar is dark and non-reflective, absorbing heat and increasing building cooling demand; disposal of coal tar products also raises environmental concerns in some jurisdictions.

Safety And Regulatory Considerations

Hot applied tar presents safety hazards including burn risk and fumes; professional installation and emergency planning are essential.

Silicone emits low VOCs compared to solvent-based materials, but installers should follow manufacturer safety data sheets for proper PPE and ventilation practices.

When To Choose Silicone Over Tar

Silicone is recommended for flat or low-slope roofs prone to ponding, terraces, or roofs requiring long-term waterproofing and UV resistance with minimal maintenance.

Silicone Is Also Appropriate For Metal Or Aged Single-Ply Roofs where replacing the membrane is costly but a seamless coating can extend service life.

When Tar Might Be Appropriate

Tar may be suitable for some built-up roofing systems, flashings, and temporary patching where compatibility with asphalt-based layers is required and short-term cost is prioritized.

Existing roof conditions and local contractor expertise sometimes dictate tar use, especially in regions or applications with long-standing built-up roof practices.

Common Misconceptions And Practical Tips

Misconception: All coatings are interchangeable. In reality, substrate compatibility, climate, and roof slope determine the appropriate choice.

Tip: Conduct a moisture scan and surface test before coating; trapped moisture under coatings leads to blistering and adhesion failure regardless of product type.

Maintenance Checklist For Each System

• Silicone: Annual inspections, clear debris, check seams, patch punctures, consider reflectivity washing.
• Tar: Regular inspections, re-seal seams and flashings, replace brittle patches, monitor for ponding areas.

Cost Example And Return On Investment

Example: A 5,000 sq ft flat roof might cost $1.50–$3.50/sq ft for tar maintenance versus $4–$9/sq ft for a silicone coating system installed professionally.

ROI Consideration: Silicone’s longer life and energy-savings from reflective options typically yield lower total cost of ownership over 10–20 years.

Choosing A Contractor And Warranty Factors

Select contractors with specific experience in the chosen material and request references, project photos, and independent reviews to verify workmanship.

Warranties differ: Silicone manufacturers often offer 10–20 year warranties; tar systems may have shorter warranty periods and more caveats for maintenance.

Key Questions To Ask Before Deciding

1. What is the roof substrate and current condition?
2. Is ponding water present or likely?
3. What is the expected service life and maintenance budget?
4. Are energy savings via reflectivity a priority?

Final Decision Factors

Prioritize long-term waterproofing, UV resistance, and lifecycle costs when selecting between roofing tar vs silicone for flat and low-slope roofs.

In Many Cases, Silicone Provides Superior Performance for ponding water, UV stability, and lower maintenance, while tar remains an option for specific asphalt-compatible assemblies and short-term repairs.

For personalized guidance, a professional roof assessment with substrate testing and an itemized quote will ensure the chosen system aligns with budget, climate, and building goals.