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We see a lot of questions about ice and water shield and what kind of protection it can offer. Is it necessary? Can it be left exposed? What, exactly, does it do that regular underlayment can’t do? We have the answers to these questions and more below!

What is Ice and Water Shield?

The definition of ice and water shielding is simple: It’s a layer of peel and stick underlayment that you put in place to protect a roof deck against damage from rainwater, ice, melting snow, and other sources of moisture. It needs to be a peel-and-stick underlayment because these underlayments don’t use fasteners but do create a completely impermeable barrier against moisture.

Typically, you’d place ice and water shield in areas most vulnerable to moisture damage. That includes along the edges of the roof, in valleys, and around openings for things like chimneys and vents.

Epilay’s Plystik Plus is a tough peel-and-stick underlayment that makes a great ice and water shield—and it comes with Ice Dam Protection, which means that it’s been designed to prevent damage where ice dams form along the edges of the roof.

How Long Can It Be Exposed?

The answer to this question will vary by manufacturer. Each will have different standards for its product.

For Plystik Plus, the underlayment can be left exposed and will remain water repellent, non-absorbent, and UV-resistant for up to 180 days.

Can It Get Wet?

Yes! So long as the underlayment has been installed correctly to ensure that it forms a watertight barrier, and as long as it hasn’t been left exposed to the elements too long, ice and water shield can get wet. It’s designed to be the last line of defense against moisture to prevent damage to the roof deck.

However, keep in mind that it is the last line of defense. If there’s an issue with the roof’s primary surface material that is allowing excessive moisture beneath that surface, it’s a problem that should be corrected to preserve the life of the entire roofing system. For instance, if shingles are lifted during a windstorm, it’s better to fix this problem than to rely on the underlayment alone as a moisture barrier.

How Long Does It Last?

Again, this will vary by manufacturer. As mentioned above, Plystik Plus will last up to 180 days when left exposed. Without exposure to the elements, Plystik Plus offers a limited lifetime warranty, which means that with proper installation, you’ll get decades of use from it.

Can I Use It on the Entire Roof?

Yes, you can use Plystik Plus or another peel and stick underlayment over the entire roof! For high elevation, high wind, or wind-driven rain we recommend that you cover the entire roof deck with Plystik Plus. However, many builders and roofers only use it on areas more likely to see water damage—like the edges, valleys, and around openings. That’s because peel and stick underlayment is one of the more expensive underlayment products out there, so using it only in vulnerable spots helps keep costs down.

Is It Required?

Even though ice and water shield is a smart idea, it isn’t always required. The main thing is to make sure that you check local building codes. While many areas have no provisions for this, other places—like Florida—have tougher building codes where underlayments with high tear strength and wind resistance are required.

No matter the climate, ice and water shield is always a good idea. Think of it as insurance. It’s an extra line of defense that protects the structures beneath against potential damage from water infiltration.