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Drying In A Metal Roof [Why + How To + Roofing Underlayment]
Lauren Risotto

By: Lauren Risotto on December 9th, 2020

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Drying In A Metal Roof [Why + How To + Roofing Underlayment]

Metal | Roofing


It’s common for issues to arise on a construction site that inevitably delay your project. When it comes to roof installation, this could mean anything from the delivery of the roofing materials being delayed to the installation taking longer than expected.

No matter the circumstances, the home needs a temporary covering so it can be protected and not be damaged from the elements.

At Western States Metal Roofing, we manufacture metal roofing and siding and also offer all of the materials you’ll need for a successful roofing installation including when you need a temporary roof.

In this article, we go over what you need to know when you have to dry-in a roof.

Drying In A Roof: What To Do When Your Metal Roof Project Is Delayed

What Is Drying In A Roof?

“Drying In” is short for dry inside. It means to make the roof impermeable to rain and weather. A roof dry in is accomplished by installing a roofing underlayment on top of the wood substrate of the roof. Roofing underlayment functions as a weather-protected covering that will keep the inside of the structure dry.

The roofing underlayment is installed before the installation of the roofing material has begun. This way your roof is exposed to weather while you wait for the roofing materials to be manufactured and installed.


Why Is Drying In A Roof Important?

Imagine if you left the top down on a convertible parked outside and then a massive rainstorm happened. The interior of that car would end up with water damage that would have easily been preventable. The same is true for a house or structure that is in the middle of installation and doesn’t have a temporary roof. Drying in is a preventative measure that will keep the structure’s interior sealed and protected.

This is such an important step of a metal roofing installation that we have written an entire article about it.

Does Metal Roofing Need Underlayment? A Guide For Homeowners.


How To Dry In A Roof

Drying in a roof is done by installing roofing underlayment. If you're re-roofing, it’s installed after the old roofing material has been removed. Prior to installing any underlayment, make sure the roof is clean and clear of any debris, nails, or staples.

On a new roof, the roofing underlayment will be installed on the wood substrate prior to installation of the metal roofing and flashings.

Installing the roofing underlayment correctly is crucial, especially when leaving the roof exposed. Incorrectly installing the underlayment can lead to leaks, which defeats the purpose of drying in a roof.

Discover the tools you’ll need to install synthetic underlayment plus simple step-by-step instructions on how to install the underlayment by watching:


Choosing Between Synthetic Roofing Underlayment And Felt Roofing Underlayment

There are two types of underlayment: felt and synthetic. Felt underlayment was around for many years before synthetic underlayment came onto the market.

Synthetic underlayment was created as an answer to address the shortcomings of felt underlayment. It’s made from sheet products made of laminated polypropylene or polyethylene plastic. This makes the product more durable than felt with excellent resistance to the elements. It can withstand hail better than felt and can be exposed to UV rays for longer periods of time.

While felt underlayment is more affordable, it was designed to not be left exposed. Synthetic underlayment, on the other hand, can be left exposed and will not absorb moisture.

Metal roofing is simply an attractive shell that’s designed to protect the roofing underlayment.

In fact, choosing the correct underlayment might be the most important decision when choosing your metal roofing materials.

Sharkskin Underlayment Comparison Guide


When To Not Use Synthetic Metal Roofing Underlayment

Synthetic underlayment is the recommended choice when drying in a roof. However, you should always refer to the building code prior to finishing the roof installation. There are certain building codes that require felt underlayment.


How Long Can Synthetic Underlayment Be Left Exposed?

It’s always best to cover the roofing underlayment as soon as possible. The amount of time you can keep synthetic underlayment exposed depends on the type and brand of the underlayment.

They can range anywhere from 2 months up to 12 months and will still remain weathertight.

Underlayment is also rated for its UV resistance. The lower end synthetic underlayments are usually rated for 6 months of UV resistance and the more expensive underlayments will be rated for 12 months.


Dry-In Site Inspections

During construction, multiple inspections will occur by the city in order to ensure building codes are being followed. A dry-in inspection is performed after the flashings and the roofing underlayment installation has been completed.

An inspector will come out to the job site to check:

  • Roofing Underlayment
  • Metal Roof Flashings
  • Drip Edges (if applicable)

The inspection is performed to verify that the metal roofing installation has been done correctly and that the right materials were used.

A secondary water barrier compliance affidavit is completed and submitted with photos that specify the details of the project, including the type of underlayment that is being used for the temporary roof. Although not always required, generally a city will only need to perform one final inspection at the end of construction if they receive a correctly completed affidavit.


Getting Started On Your Metal Roofing Project

If you anticipate having a gap between the old roof being removed and the new roof being installed, you will need to dry-in the roof.

Not only is roofing underlayment the first step of your installation, but synthetic underlayment also has additional benefits:

  • Can last up to twice as long as felt underlayment.
  • A lightweight material that is easy to install and safer to walk on than felt.
  • Lays flat for a smoother appearance on the roof decking.
  • Offers resistance to mold and mildew.

Western States Metal Roofing has synthetic metal roofing underlayment ready to be shipped immediately in addition to all of our other roofing products and accessories. We are happy to help and can also provide you with a free quote for any of our products.


Request A Quote Roofing Underlayment

About Lauren Risotto

Lauren is the Content Manager at Western States Metal Roofing and provides insight on content creation and product promotions.