Ponding water is one of the most common — and frustrating — issues on flat commercial roofs. It leads to leaks, material breakdown and expensive repairs if left unchecked. That’s where SL-851, a two-part, ponding water eliminating coating, comes in. Whether you’re a roofing contractor or facility manager, this product gives you a fast, permanent fix for low spots and foam blisters.
We broke it down in a recent Progressive Materials University (PMU) episode, and here’s what you need to know.
What Is SL-851?
SL-851 is a two-part urethane-based roofing compound made with recycled EPDM and EPS pellets. It’s tough, waterproof and eco-friendly — a rare combo. Designed for flat or low-sloped roof ponding water repair, it’s perfect for areas around drains, scuppers or anywhere water likes to sit.
You can apply it up to 4 inches thick. At 4 inches, it cures fully in 24 hours and is ready to be coated.
What’s Inside the Bucket?
Each SL-851 kit includes:
- A small bag with gloves, a chip brush, mixing bag and instructions.
- A half-gallon of urethane binder (buried in the granules).
- A large bag of granules made from recycled roofing materials.
To prep it: dump the granules in the mixing bag, add the binder and knead it until it’s evenly mixed. Once that’s done, you’re ready to apply it directly to the roof.
How to Apply SL-851 on Flat Roofs
This silicone low spot filler works on a range of roof types, including:
- TPO
- PVC
- Modified bitumen (Modbit)
- EPDM
- Spray foam roofs
When filling foam blisters, as seen in this video, PM Technical and Education Coordinator Jeff Romero recommends cutting the blister out with a slight bevel and packing the void with SL-851 using a trowel. After it cures, coat the area with silicone or acrylic — whatever matches your system.
Why Use SL-851 for Ponding Water?
Here’s why contractors are making the switch:
- Fixes ponding water on flat roofs
- Made with recycled materials
- Fast 24-hour cure time at 4-inch depth
- Compatible with most commercial roof types
- Tough, impact-resistant finish
- Ideal for low spots, dips, and foam blisters
It holds up to foot traffic, weather and wear once it’s cured. We’ve hit this stuff with hammers in demos — it doesn’t flinch.
Ready to Eliminate Ponding Water?
If you’re tired of patching the same low spots or watching water pool after every storm, SL-851 is your solution for flat roof ponding water repair. Contact your regional manager here for pricing and application support. Not sure who to call? Visit pmsilicone.com to get started.
And if you want more how-to videos and product walkthroughs, check out Progressive Materials University on YouTube. Like, subscribe and get better at roofing.
