You’ve got a leak. It’s 2:00 PM on a rainy Tuesday, water is dripping onto a stack of inventory, and your maintenance guy suggests running to the hardware store for a bucket of “roof cement.” It sounds like the perfect, cheap solution.
But before you let anyone climb that ladder with a trowel, you need to hit the pause button.
In the world of commercial roofing, roofing tar (or mastic) is a polarizing tool. Used on the right roof, it’s a miracle worker. Used on the wrong roof, it is arguably the most destructive thing you can apply. We have seen thousands of dollars in damage caused by a $20 bucket of tar applied to a modern single-ply system.
At Premier Group, we want to save you from that headache. Whether you are managing an emergency leak or planning your winter roof prep, understanding the chemistry of your roof is critical. Let’s break down exactly when roofing tar for commercial repair is your best friend, and when it’s your worst enemy.
What Is Roofing Tar, Anyway?
In simple terms, roofing tar is a dark, oily mixture derived from coal treatment or petroleum byproducts. It is thick, sticky, and waterproof. For decades, this was the industry standard. It was the “duct tape” of the roofing world, cheap, accessible, and effective at stopping water instantly.
However, roofing technology has evolved. Today’s commercial roofing market is dominated by high-tech synthetic membranes like TPO and EPDM. These materials are chemically engineered, and they do not play nice with old-school petroleum products.
When It Works: The Asphalt Family
Roofing tar is excellent when it sticks to its own kind. If your building has an asphalt-based roof, tar is usually a safe and effective choice for emergency roof repair.
Built-Up Roofs (BUR)
If you have a “tar and gravel” roof (layers of felt and asphalt topped with stone), roofing tar is compatible. It bonds perfectly with the existing bitumen, allowing you to seal cracks or flashings effectively.
Modified Bitumen
Modified Bitumen is essentially the modern evolution of the asphalt roof. Since it is asphalt-based, it can tolerate roofing tar for temporary patches. However, even here, you have to be careful. Some “Mod Bit” systems are applied with torches, and smearing solvent-based tar on them can create fire hazards or adhesion issues during future permanent repairs.
The “Emergency” Exception
In a true catastrophe, where water is pouring in and the roof is already destroyed, tar can stop the bleeding on asphalt systems. But remember: Roofing tar is rarely a permanent fix. It dries out, cracks under UV rays, and eventually re-opens the leak.
When It Doesn’t Work: The Single-Ply Danger Zone
This is the section that could save you ten thousand dollars.
If you have a white roof (TPO) or a black rubber roof (EPDM), DO NOT USE ROOFING TAR.
The TPO Disaster
TPO roofs (Thermoplastic Polyolefin) are plastic-based. Tar is petroleum-based. When you apply tar to TPO, two things happen:
- It Won’t Stick: TPO is slick. The tar might look like it’s holding, but water will eventually creep underneath it.
- It Ruins the Repair: TPO is designed to be heat-welded. To fix a puncture properly, we use a robotic welder to fuse a new patch onto the existing membrane. If you have smeared tar over the hole, we cannot weld to it. We have to cut out the entire contaminated section of the roof and replace it. A simple $200 patch job turns into a major surgical procedure.
The EPDM Nightmare
EPDM systems (Ethylene Propylene Diene Monomer) are synthetic rubber. Petroleum solvents eat rubber.
If you put roofing tar on an EPDM roof, the rubber will chemically react. It will swell, bloat, and eventually disintegrate into a gooey mess. You aren’t plugging the hole; you are effectively dissolving your roof.
The Alternatives: How to Fix Modern Roofs
If you can’t use tar, what should you use for an emergency roof repair?
- For TPO Roofs: Use a specialized TPO-compatible sealant (often polyurethane-based) or, better yet, a heat-weld patch installed by a pro. There are also specialized pressure-sensitive tapes (like Eternabond) that work in a pinch without destroying the membrane.
- For EPDM Roofs: Use a lap sealant designed specifically for EPDM rubber, or a cured rubber patch with a primer.
Winter Roof Prep: Tar is Not the Answer
As we approach the colder months, many building owners look to seal up their roofs. This is a crucial part of winter roof prep.
However, standard roofing tar becomes brittle in the cold. If applied in freezing temperatures, it often fails to bond and cracks immediately.
Instead of smearing tar on questionable areas, schedule a professional inspection with Premier Group. We look for:
- Roof damage from previous storms.
- Separating seams (which tar can’t fix permanently).
- Shrinking flashings.
The Cost of a “Cheap” Fix
We understand the temptation. You see roof damage, and you want it fixed now for as little money as possible.
But in commercial roofing, cheap fixes are expensive. We often get called to perform a roof replacement on a roof that should have lasted another 10 years, simply because the owner tried to DIY the repairs with incompatible materials.
The Bottom Line:
- Asphalt/Tar Roof: Tar is okay for temporary fixes.
- White Roof (TPO/PVC) or Rubber (EPDM): Tar is strictly forbidden.
Call the Experts at Premier Group
Your roof is a capital asset, not a driveway. Treat it with the respect it deserves.
If you are unsure what type of roof you have, or if you are staring at a leak and holding a bucket of tar, put the bucket down and pick up the phone.
At Premier Group, we specialize in identifying the right solution for your specific roof system. Whether you need a quick roof repair that won’t void your warranty, or a full consultation on roofing tar for commercial repair, we have the expertise to keep your business dry.
Don’t let a bad patch job ruin your investment. Contact Premier Group today for a professional assessment.