Snow does not stay put. It melts, it runs, it refreezes, and it works its way into places water is not supposed to go.
For roofing contractors working in northern markets, that cycle repeats through the entire season. A stretch of sun softens the snowpack, temperatures drop overnight, and whatever moved during the day freezes where it stopped. The roof covering handles most of it. What happens underneath the covering is where the outcome is decided.
This is where an ice and water shield earns its place in the assembly. Here we look at what freeze-thaw conditions do to a roof, which areas take the most exposure, and what a self-adhered ice and water shield brings to cold-weather work. We build three self-adhered underlayments for this category, and all three carry ice dam protection.
What Freeze-Thaw Cycles Do to a Roof
The mechanism is straightforward. Heat escaping through the roof deck melts snow higher up the slope. That meltwater runs down toward the eave, reaches the colder overhang where there is no heated space beneath it, and refreezes. Repeat that over several days and the refrozen ridge builds into an ice dam, holding standing water behind it on a roof that was designed to shed water, not store it.
Standing water backs up under the primary covering, and once it is there, gravity stops helping. Water can travel uphill under shingles when there is enough of it and enough time. The layer directly beneath the covering becomes the last line of defense, and it has to perform while the deck contracts, expands, and cycles between wet and frozen. That is the condition an ice and water shield is specified for, and it is what we built our self-adhered Epistik line to handle.
Where Protection Matters Most
Not every square of a roof faces the same winter exposure, and that is what drives where ice and water shield coverage is called for. Eaves take the worst of it because that is where the warm section of the deck ends and the unheated overhang begins. Valleys concentrate runoff from two planes into a single channel that ices readily. Transitions and penetrations interrupt the continuous plane of the roof, and any interruption is a place where water can find an edge.
How much of the roof gets covered, and how the membrane is placed in those areas, is governed by local code and by the manufacturer’s written instructions. Rather than working from general practice, we would encourage roofing contractors to confirm placement against the documentation for the specific product on the job. We publish installation instructions and technical data sheets for every product in our downloads section at epilay.com, in English and Spanish.
Why Self-Adhered Works in Cold Weather
A self-adhered ice and water shield bonds to the deck across its full surface rather than being held at fastener points. Our Epistik products use an SBS modified bitumen adhesive that performs well in high and low temperatures alike, with a split release liner coated on both sides to make the sheet easier to work with. Full-surface adhesion also means the membrane seals around fasteners driven through it, and all three Epistik products report a pass result for nail sealability under ASTM D1970, the standard that governs self-adhered ice barriers.
Cold-weather behavior is the other half of it. Our Epistik products do not wrinkle, crack, or become stiff in colder temperatures, and they will not dry out or leach oil in high heat the way asphalt-based products can. Those properties are documented in the approvals the line carries. Epistik is covered by Intertek’s Code Compliance Research Report CCRR-1083, carries Florida Building Code and Miami-Dade approval, is approved by the Texas Department of Insurance, and is approved for use in Class A fire-rated roofing assemblies as described in CCRR-1083.
Installing in Cold Conditions
Winter work adds variables that a summer install does not have. Our installation instructions address material interface temperature, weather conditions at the time of application, deck surface condition, priming requirements that differ depending on whether the deck is wood, concrete, or masonry, and how the rolls should be stored and conditioned before they go up. Those requirements are stated precisely in the product documentation, and the documentation is where they should be read rather than approximated on site.
Two points are worth knowing before the truck is loaded. Our instructions direct that the product is not to be installed over an old roof covering, which matters on winter re-roofs where tearing off feels like the harder option. And for clearing ice from a surface, our instructions specifically direct against using salt. Neither of these is a judgment call. Both are published requirements, and both are the kind of detail that is easier to plan around before the crew is on the roof than after.
Choosing the Right Epilay Product
Our self-adhered lineup covers three products, and all three carry ice dam protection. Epistik Ice & Water, also written as Epistik I&W, is a granulated, fiberglass-reinforced SBS modified bitumen membrane with a gray GripWalk top layer. We built it as a replacement for traditional sand and granular peel and stick underlayments, which is the category most roofing contractors have in mind when they specify an ice and water shield. Epistik Plus is a five-ply synthetic construction with a light grey GripWalk high-traction top surface, and the light color reduces heat for a cooler working surface. Epistik SA-250 uses a three-layer facer with a deep-embossed blue top surface and its own high-traction walking surface.
What the three share matters as much as what separates them. Each is a self-adhered membrane with a lifetime limited warranty, each reports nail sealability under ASTM D1970, and each falls under the same set of approvals: CCRR-1083, Florida Building Code, Miami-Dade, and the Texas Department of Insurance. For work in Miami-Dade and Broward counties, stricter high-velocity hurricane zone requirements apply, and the fastening pattern specified in the Miami-Dade Notice of Acceptance is the one that governs.
There is a systems argument here as well. A sealed roof deck is one of the core requirements of the FORTIFIED standard from the Insurance Institute for Business and Home Safety, and a fully adhered membrane over the deck is one of the recognized ways to achieve it. Our underlayments are approved for use in FORTIFIED roof systems, which puts the same product that solves a freeze-thaw problem in the north into a program that opens grant and insurance-discount conversations in other markets.
Selection comes down to the deck, the primary covering, and the exposure the roof will see. We publish the specifications, technical data sheets, and approval documents for each product at epilay.com so the comparison can be made against documentation rather than description.
Go Into the Season Prepared
Freeze-thaw exposure is predictable. It arrives every year, it concentrates in the same areas of the roof, and it rewards the assemblies that were specified for it. A self-adhered ice and water shield is the part of that assembly that keeps working after the covering has done what it can.
Our Epistik line brings full-surface adhesion, sealed fastener penetrations, cold-temperature flexibility, and the approvals to document all of it. Visit epilay.com to compare the Epistik lineup and download the technical data sheets, installation instructions, and approval documents for each product. For help matching a product to a specific job, contact us.
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