How to Dry In a Metal Roof: Products, Techniques, Best Practices

What type of underlayment should you use and how do you install it on your roof?
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Installing underlayment or "drying in" your roof ensures that your building is protected by a weather tight base while the roofing substrate is attached, and it serves as a backup if water ever penetrated the main assembly. Today on The Metal Roofing Channel, Sheffield Metals Assistant Technical Director Dave Stubbs explains the main differences between types of underlayment products, when you should choose each type, and best practices for installation.
Always remember to follow manufacturer's installation guidelines.
Please note the installation details and methods shown in this video are for reference only. Sheffield Metals recommends following their published installation details or for WTW projects following the required details issued and marked approved for that specific project.
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[@sk8rhippie]

Great questions!! Thanks for all the great advice!

[@TheMetalRoofingChannel]

Glad it was helpful! -Thad

[@KevinCGleason]

Thanks again Thad. Just fired my roofing contractor on 9/11 because there was NO PROGRESS since my contract signing on 4/30! Just met with 2 other roofers for estimates, both want to put 30 lb under the metal. Now I can ask intelligent questions.

[@613kc]

Kevin, Life's hard right now (Sorry to hear your situation). Wonder how common your story is? (ie Kids going back to school or not?) Wearing mask raises my blood pressure. Through the filthy thing out yesterday. No More!

[@TheMetalRoofingChannel]

Glad we can help you ask the right questions, Kevin. Finding the right contractor is extremely important. Here's an eBook we did that covers how to prepare for your installation: bit.ly/installation-success-ebook It may give you some additional things to think about. Good luck with your project! -Thad

[@tanshihus1]

Any special tools or extra fastening needed for use with the Sharkskin peel and stick

[@firemanwill28]

Any input on putting a self adhered underlayment on a wet roof?

[@kbushee88]

Hey Thad and David, what would you recommend for UL for Vermont utilizing a snap-lock standing seam system. It will be going on a house with sheathing (½” standard)
Thanks guys!

[@TheMetalRoofingChannel]

Being in snow country, a fully adhered underlayment would most likely be your best bet. We use Sharkskin Ultra SA for that application. Hope that helps! -Thad

[@GeneFlygene]

Great info. How would Zip sheathing the brown roof 5/8” comparison with the shark skin? Would you need the shark skin or could you go right over the Zip with your metal roof? Thanks.

[@TheMetalRoofingChannel]

Here are some things to consider with the Zip System: I would always continue to use an underlayment no matter what. These Zip products need to be taped and rolled at the seams correctly, seams have to have proper spacing, and all over-driven nails need to be sealed. There is a chance some areas might be missed, so using a quality peel & stick as a secondary defense is a good practice. My suggestion for roof decking is ½” minimum plywood or 5/8” OSB which are close in fastener pull-out values, so you are making the right choice there. Hope this helps! -Thad

[@AUCTIONEER816]

Peel and stick does not breath and greats a ton of heat which can breakdown the underlayment itself.

[@celinesholdice5160]

Our contractor put metal on to the actual rafters. We are in Canada.

[@iancormie9916]

if you are in snow country and apply a fully adhered membrane - will you have a problem with water condensing con the underside of the membrane causing rot? The reason I ask is a lot of cold weather districts call for a vapor barrier in the inside surface which means the roof could not try to the inside.

[@seananderson2568]

If the atic space is properly ventilated a sealed deck wont cause any problems. Most roof systems are basically impermeable without peel and stick anyway. Almost all synthetic underlayment is impermeable when applied

[@shawnmoats9526]

Mr. Anderson is correct. If you simply look at one component of your roofing system without being well versed in the IBC or RBC (also this year we will begin to see alot more of this issue as now the Energy Code has changed as well) , you will most likely be overlooking the ventilation requirements. In cold environments, it is imperative to do a proper ventilation calculation to insure you have the proper venting system in place to vent the moisture laden air BEFORE it can condense. If you are experiencing condensation under your self adhered you have a venting problem, not a roofing problem.

[@isleofgreg]

I used 5/8 Zip for my roof sheathing and since it has the WRB built in, they said just screw the metal sheets directly to that, so that's what we did.

[@613kc]

What about seams? You applied tape?

[@isleofgreg]

@@613kc I used liquid flashing (Dymonic 100 black) at the seams but the Zip tape would have worked just fine too

[@nailbenderMatt]

I’m not sure if you did the right thing. But, I will say: I put a piece of 1/2” Zip in a bucket of water for more than a year. While it did swell to 3/4”. But, it was structurally solid after that........

[@CuttingEdgeMR]

Dudes crazy on valley underlayment, you weave the adjacent first course bottom eave rows only, then you run a full valley piece from top to bottom. The remaining courses get cut 6-10" out of the center of the valley, on the valley angle.