Since their entry into the mainstream market, liquid flashing has become one of the core parts of any modern home weatherproofing setup, being especially invaluable around plumbing, windows, and other small points of ingress.

Of the many options for liquid flashing available on the market right now, two products, in particular, are considered the most popular among home builders and homeowners: the ZIP System Liquid Flash from Huber and the R-Guard FastFlash from Prosoco. 

Why exactly are they so popular? Which one should you choose between the two?

What factors should you consider before you settle on either of the two liquid flashing products? Follow along on our ultimate comparison below to help you find which product works best for your home.

    Zip System Liquid Flash Overview

    The ZIP System Liquid Flash is a premium liquid-applied flashing membrane used in home weatherproofing systems. Being part of the ZIP System, Liquid Flash is intended to be used alongside other ZIP System products, which include a vapor barrier sheathing and flashing tape

    Liquid Flash is manufactured by Huber Engineered Woods, a manufacturer of building products based out of Charlotte, North Carolina, that also provides engineered wood structures for home framing.

    ZIP Liquid Flash is best suited for spaces that are too tight or otherwise too difficult for “hard” weatherproofing—spaces like the areas where door and window frames meet the home’s main wall structure, among others.

    Works with ZIP System air/moisture barrier for maximum sealing
    Up to 180 days of weather exposure
    Easy to caulk and spread even in strong weather
    Not available in roller-grade form
    Does not inhibit mold growth

    Prosoco R-Guard FastFlash Overview

    FastFlash is the all around liquid flashing solution in the R-Guard line of air and water barriers. As the name suggests, R-Guard FastFlash is intended to be used alongside other R-Guard products for optimal effectiveness. 

    The manufacturer of FastFlash, Prosoco, also produces a variety of other specialty construction products including cleaning and care chemicals for buildings, concrete flooring maintenance tools, and construction anchors. 

    FastFlash, like other liquid flashing products, is intended to be used to seal tight corners and crevices where your typical weather-resistant barriers won’t be able to cover as cleanly.

    Versatile weatherproofer and sealer
    Available in gun-grade and roller-grade variants
    Can be exposed to weather and UV for up to 12 months
    Handles rain immediately after application
    Seals around nails and fasteners
    Not available in smaller sizes
    Relatively slow cure time

    Application Comparison

    As they are competing types of liquid flashing, both Prosoco R-Guard FastFlash and ZIP Liquid Flash are used to do more or less the same things—sealing doors, windows, and other tight or tricky spaces where vapor barriers, flashing tapes, and similar weatherproofing components can’t quite seal properly. 

    Of course, there are a few subtle differences between FastFlash and Liquid Flash that most might not notice but can be something to look out for if you plan to use liquid flashing. Here are a few of our observations:

    • Both products are intended to be used with their companion product lines. In other words, the manufacturers recommend using ZIP System Liquid Flash with other ZIP System products, and R-Guard FastFlash with other R-Guard weatherproofing solutions on your home for the best results. 
    • We found that ZIP System Liquid Flash is a bit more viscous than FastFlash. From our testing, the extra viscosity makes it a bit easier to work with when applying the liquid flashing to seams on the roof. 
    • ZIP Liquid Flash is rated to have a fast curing time of 20-40 minutes depending on the weather conditions, which is quite a bit faster to the 30-60 minute estimate for FastFlash. As such, one might want to use the ZIP flashing in situations that require a bit more speed.
    • ZIP Liquid Flash is capable of covering a larger area on the same volume of flashing. On a 20-ounce sausage container, the ZIP System product can cover up to 22 linear feet as opposed to around 17 linear feet with the Prosoco FastFlash. 
    • Prosoco FastFlash is rated to withstand UV and weather exposure for up to a staggering 12 months. While the ZIP product can last for a respectable 180 days (or about 6 months), the extra life provided by Prosoco’s FastFlash does allow longer stretches of inactivity on a house build.
    • Prosoco FlastFlash comes in a special roller-grade version that allows for much wider coverage, extending its possible applications to include sections of flat walls that need a bit of extra protection from water and air.

    Pricing Comparison

    Cost is one of the most important considerations for anyone choosing between the better of two very similar products—however, factoring in pricing is also the trickiest as it can vary quite widely depending on where you are.

    At the time of writing this guide, a 20-ounce sausage pack of ZIP Liquid Flash can be bought for around $32, while an equivalent size of Prosoco FastFlash costs around $28 a piece. While this $4 difference might be enough of a difference to warrant picking Prosoco as your flashing, one should keep in mind that this pricing can and will change.

    Besides that, it is also important to factor in the characteristics of the flashing you’re buying into the cost. For instance, ZIP Liquid Flash may be more expensive, but our testing has found it to cover a bit more area given the same volume of flashing.

    On the other hand, Prosoco FastFlash also comes in a slightly different formulation for use with rollers, which is a lot more economical if you plan to coat a much larger area in flashing. 

    Longevity Comparison

    Another important quality to think about is the longevity and durability of the flashing you plan to use. 

    We have already covered previously that ZIP Liquid Flash and Prosoco FastFlash each have their own unique qualities when one considers what they are capable of standing up to.

    In this regard, we do like that Prosoco FastFlash has the UV stability and weather resistance to last up to 12 months after application, which can make it the preferred choice if your home’s construction job is expected to deal with extended shifts in schedule.

    That being said, the 6-month rated exposure time that ZIP Liquid Flash has is more than enough leeway for most construction projects; taking this into consideration along with their other features, ZIP can be a viable option if extreme longevity is not a fixed requirement. 

    Editorial Contributors
    avatar for Matt Greenfield

    Matt Greenfield

    Matt Greenfield is an experienced writer specializing in home improvement topics. He has a passion for educating and empowering homeowners to make informed decisions about their properties. Matt's writing focuses on a range of topics, including windows, flooring, HVAC, and construction materials. With a background in construction and home renovation, Matt is well-versed in the latest trends and techniques in the industry. His articles offer practical advice and expert insights that help readers tackle their home improvement projects with confidence. Whether you're a DIY enthusiast or a seasoned professional, Matt's writing is sure to provide valuable guidance and inspiration.

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