PROSOCO FastFlash | Waterproof and Airtight Fluid-Applied Flashing Membrane - Trusted by Professionals

Prosoco R-Guard Fast Flash (and related Joint & Seam Filler) works as described to seal the gaps between different building materials. Tape and caulk products aren't all-purpose as liquid flashing products, where you apply a large bead in bulk, and then spread as needed for the situation. Corners, odd shapes, vertical, horizontal, works equally well inside tight spaces as it does across large flat areas. You can push the liquid flashing into cracks in the same way that caulk is applied, plus you spread it out with a plastic fin or other spreader tool. Cleans up easy with paper towels before it dries. The finished product is a rubberish mastic that provides a permanent barrier to water, air and insects.Cure (drying) time is dependent on humidity. If you're working in a very dry environment (e.g. below 50% humidity), a small amount of water misting with a spray bottle will speed things up. I'm in central Texas and find most days that I can spread the joint and seam filler in the morning, and then after lunch apply the fast flash. On especially dry days (humidity below 30%), I'll very lightly mist the substrate before applying the joint and seam filler. A great benefit, rain isn't a worry - you can apply these products and not worry about rain later in the day!The joint and seam filler is pink and reinforced with fibers, designed to fill large gaps between material, goes on very thick and the finished surface isn't as smooth/flat in comparison to the fast flash.Fast flash can be used by itself, or on top of the joint and seam filler. Dark red in color, nearly the same product as the joint and seam filler, but less fiber reinforcement to allow being applied as a thin top-coat that finishes smooth and sexy!Applied successfully at the foundation between concrete and base angle (e.g. sill plate) for metal buildings, workshops, and barndominiums. Works great for commercial and residential construction across a wide variety of materials!

This stuff is amazing. Great grip, easily seals even big gaps for a smooth waterproof seal. Used on window rough openings, but will work anywhere you need waterproofing

I used this to seal the transition between OSB sheathing and sill plates that are sitting on concrete. It was easy enough to apply, although more liquid than expected. Once cured, it felt like rubber and it gives me confidence that it's a great seal. It took two sausages to cover 40 feet of sill plate.

Great product. I would buy more from Amazon if shipping wasn’t so long. Otherwise, I get it from Small Planet.

The Prosoco R-Guard FastFlash Liquid Flashing Membrane exceeded my expectations in sealing and protecting my home. Its easy application and fast-curing formula make it ideal for sealing complex joints and penetrations. With its durable adhesion and flexibility, it provides reliable protection against water intrusion and air leaks. The 20oz sausage packaging is convenient and mess-free, making the application process a breeze. Whether you're a professional contractor or a DIY enthusiast, this product is a must-have for any construction project requiring top-notch waterproofing.

Works, but a little spendy. Need to sell a 2, 3, 4 pack for cheaper or something

Amazing product, excellent for sealing windows!

Pretty easy to tool even in cold temps, initial tack very good, sag resistant but self levels a bit (I probably used it where I should've used the joint filler in some cases.) Is just nice to work with...when paper towels are readily available to keep the spreading tool and all of one's clothing clean. I can't review the properties I can't test such as breathability etc but it'd have to be far better in that regard than the off the shelf caulk type products.