When you have a new metal roof put on, the roofing contractor will probably tear all the old roofing down to the deck. When the new roof is put on, underlayment is normally fastened to the deck before the metal roofing is applied. Here's a look at why your metal roof needs underlayment, and the types to consider for your house.

Why Metal Roofs Need Underlayment

Underlayment is a barrier that goes between the metal panels and your roof deck. The barrier keeps moisture away from the deck and also helps muffle noise. In addition, the barrier can keep your attic from getting too hot since a metal roof heats up in the sun. Also, the underlayment provides a surface for the metal panels to rest on as the panels expand and contract with weather changes.

How Underlayment Is Installed

Underlayment is applied in sheets on your roof and fastened with capped nails. Some underlayment has an adhesive backing that sticks to the roof to hold it in place. Once the metal roofing panels are installed, they hold down and hide the underlayment. However, while your roof is being put on and the roof is exposed, the underlayment doubles as a protective roof covering that shields the deck from rain.

A roofing contractor wouldn't leave the deck of your roof uncovered, but as long as the underlayment is in place, rain won't hurt your roof if a storm comes up while the roofers are working. However, the underlayment has to be securely attached so it doesn't blow off, and that's why it's nailed or adhered to the roof.

How To Choose The Right Underlayment

There are three types of underlayment for metal roofing: felt, synthetic, and self-adhering membrane. They all perform the same job, but they have different qualities. Felt is the least expensive and might be used if you are on a tight budget, but it doesn't last as long as other types of underlayment.

It might be best to choose underlayment that lasts as long as your roof is expected to last. Other things to consider are how well the underlayment blocks water vapor, how well the underlayment allows ventilation, and how well the materials tolerate high heat.

A metal roofing contractor can help you choose the best underlayment for your roof based on the slope of your roof, your budget, and your local codes. When your metal roof is installed over quality underlayment, your home has the best protection against strong winds, driving rain, and roof leaks.

Keeping water away from the roof deck is essential, or the deck will slowly rot until a roof leak develops, and then you'll have to pay for roof repairs.

If you are in need of a new underlayment, contact a local metal roofer such as Pacific Sheet Metal, for more information about the best materials for your roofing needs.