Does a Metal Roof Need an Underlayment?

There are Stages to a Roofing Project

The modern roof has multiple layers.  On top of the rafters or joists there is sheathing.  Generally made from half inch OSB or plywood, this is what provides the bulk of the support for anything that hits, lands, or walks on top of your roof.  That sheathing is covered with an underlayment that is designed to be waterproof, helping to stop any moisture that makes it past the shingles or metal.  Over the underlayment the shingles or metal is applied.

Roofing Underlayment on a custom metal roof

There are some roofers out there that believe that since metal is such a great material, and since it generally comes in large sheets making it all but impermeable, they can skip the underlayment section and attach the metal directly to the sheathing.  Their attempt to save money may cost them more in the long run.


Does my Metal Roof Need an Underlayment?

The simple answer is yes, your roof does need an underlayment.  But there are some caveats that go with that, and it depends on a variety of factors.

Gable to Gable metal roof in MontanaTraditionally built homes will need an underlayment.  If your home is built with joists, insulation between those joists, and sheathing, then an underlayment is needed before you put on a metal roof.  Basically any house in Montana, from Billings to Philipsburg to Zortman is going to be built this way.  But there are parts of the home that differ.

A covered patio may not need an underlayment.  If your patio has open beam architecture, and is designed to have a roof consisting of structural metal panels (that is, the panels attach directly to the beams without any sheathing) then you don’t need an underlayment.

If your metal roof is going on top of asphalt shingles, then there is already an underlayment, and it likely doesn’t need another.  Keep in mind, however, that expansion and contraction of the shingles could cause damage to the back of the metal over time.  It’s for this reason that Beartooth Metal Roofing in Billings always tears off the old shingles before applying a new roof.

There are some metal manufacturers that require an underlayment in order to keep the warranty valid.  Some go even further and require a self-adhering underlayment throughout the entire roof deck.  It is a more expensive method, but it will last a whole lot longer and be a whole lot more weather proof.


Beartooth Metal Roofing Doesn’t Cut Corners

Full metal roof Montana and WyomingSkipping the underlayment on your home will save you money… in the short run.  Depending on the size of the house you might save a few hundred to over a thousand dollars on the cost of your roof.  But cutting corners on this important step could end up costing you many thousands of dollars down the road.

The underlayment is a protective layer that not only protects moisture that falls from the sky, but also moisture that comes from the sky.  The difference we’re talking about is the difference between rain and dew (or frost).  Condensing moisture can get underneath the metal panels in small amounts.  With the underlayment there is nothing to worry about.  Without the underlayment, you have to deal with rotting roof decks, or sometimes worse.

If you’re putting a metal roof on your house, no matter where you live in Montana or Northern Wyoming, Beartooth Metal Roofing will make sure that it is done perfectly, and correctly, the first time.


Ready for your New Metal Roof?

Metal roofs are the perfect way to make sure that your roof looks amazing, lasts (essentially) forever, and protects your home from whatever the weather can throw at it.  Beartooth Metal Roofing serves the areas within a few hundred miles of Billings, Montana.  So if you live in Cody, WY, we can put a metal roof on your home.  If you have a cabin near Cooke City, Montana, we can get a metal roof on your cabin.  If you have a luxury mansion along the Stillwater River near Absarokee, MT, we can make it look perfect.

You get the idea.  Give us a call at 406-839-0084 to schedule a time for your new metal roof.