Re Tarring a Roof: Step by Step Guide

Re tarring a roof is a common maintenance task that extends the life of a roof by restoring waterproofing and reducing leaks. This guide provides a practical, safety‑focused approach for homeowners and professionals, detailing preparation, materials, techniques, and common issues. Proper application of roof tar, or roof cement, improves sealing around joints, valleys, penetrations, and flashing, helping to protect the structure from weather damage.

Assessing Roof Condition And Project Scope

Begin with a thorough assessment to determine if re tarring is necessary or if more extensive repairs are required. Look for visible cracks, blisters, memory of previous tar applications, and widespread coating deterioration. Inspect flashing around chimneys, vents, and joints. If structural damage, rotted wood, or extensive corrosion is present, address those issues before re tarring. For flat or low‑sloped roofs, tar can be effective, but steep pitches may require alternative waterproofing methods. Document measurements to estimate material needs.

Materials And Tools For Re Tarring A Roof

Choosing the right materials is essential for durable results. Use a high‑quality asphalt roof tar or coal tar, depending on the roof type and weather expectations. For cold weather, consider a tar designed to remain workable at lower temperatures; for hot climates, a product with better heat resistance may be preferred. Other essentials include putty knives or trowels, stiff brushes or wire brushes for surface prep, a propane torch or heat gun if hot‑tar is used, roofing cement, mineral spirits for cleanup, protective gloves, goggles, and non‑slip footwear. If membrane flashing exists, select compatible sealants and flashing cement to ensure seamless joints.

Safety Precautions And Environmental Considerations

Safety is paramount. Work on a stable surface with proper fall protection, especially on roofs with pitch. Use a sturdy ladder, secure harnesses where required, and keep a clear work area. Ventilate well if using tar products with strong fumes, and avoid applying in windy or rain‑prone conditions. Protect surrounding landscaping and water sources from spills. Dispose of tar waste and contaminated rags per local regulations. Maintain a clean work zone to minimize slip hazards and ensure safe handling of hot materials.

Preparing The Roof Surface

Thorough cleaning is critical for adhesion. Remove loose gravel, dirt, and old tar using a stiff brush and, if needed, a pressure washer on a gentle setting for flat surfaces. Allow the surface to dry completely. For cracked seams or joints, apply a compatible primer or sealant designed to improve tar adhesion. If flashing is exposed, inspect for corrosion and replace or repair as necessary before applying new tar. A clean, dry, and well‑primed surface will maximize the lifespan of the re tarred roof.

Removing Old Tar Or Contaminants

Old tar that is brittle or peeling should be removed to ensure proper adhesion of new material. Use a putty knife, scraper, or heat gun to carefully lift and remove failing sections. Surfaces with sheen or waxy residues may require a solvent wipe to remove contamination, then a light sanding to create a roughened profile for better bonding. Do not skip this step; improper surface preparation is a leading cause of premature tar failure.

Application Techniques For Re Tarring A Roof

Tar can be applied hot or cold depending on product specifications and weather. For hot‑applied tar, heat the material to a workable viscosity, then spread evenly with a trowel, ensuring complete coverage and a uniform layer. For cold‑applied formulations, apply with a trowel or brush in thin, even coats, allowing appropriate curing time between passes. Focus on high‑risk areas such as seams, joints, and around penetrations. Build up thickness gradually to avoid sagging and ensure a smooth, continuous membrane. When applying around flashing, feather the edge of the tar to blend with existing surfaces for a seamless seal.

Flashing, Joints, And Penetration Sealing

Flashing requires careful attention because failures here often cause leaks. Inspect and repair metal or asphalt flashing at valleys, chimneys, vents, and perimeters. Apply tar around flashings to seal gaps, then press in place with a roller or hand tool to ensure good contact. Use compatible sealants for joints where different materials meet. For pipe boots or vents, ensure a tight seal and smooth transition with tar. Periodically check these areas after weather events to confirm continued integrity.

Curing, Curing Time, And Maintenance

Allow sufficient curing time according to the product instructions and outdoor conditions. Temperature and humidity influence drying times; cooler weather may extend curing, while heat accelerates it. Avoid walking on the freshly tarred surface until fully cured to prevent indentations and displacement. After the initial cure, perform a visual inspection for blisters or cracks and apply a touch‑up coat if needed. Establish a maintenance schedule to inspect the roof biannually and after major storms. Reapply tar every several years as part of a broader roof maintenance plan, paired with periodic professional inspections.

Common Problems And Troubleshooting

Common issues include poor adhesion at seams, cracking around penetrations, and insufficient thickness causing leaks. If tar is cracking, remove the damaged area and re‑coat with the appropriate primer and tar, ensuring proper bonding. For poor drainage or ponding, adjust the surface slope where feasible or apply additional coats to create a continuous, watertight layer. Temperature swings can cause tar to become brittle or tacky; plan applications during moderate weather and store products away from extreme heat or cold. When in doubt, consult a roofing professional to assess long‑term viability of tar repairs.