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Roof Underlayments:  Traditional Felt vs Synthetic

Courtesy Sherriff-Goslin Roofing

Your roof is suffering from missing or buckling shingles, loss of granules or old age and it is clearly time to get a new one. A roofing contractor is called, a cool shingle design is selected and it is time for the contractor to get to work. Right? Not so fast! Before you allow anyone to jump onto your roof and start shoveling shingles, you need to know what material will be placed underneath those shingles. Your contractor will probably choose traditional felt or synthetic underlayment, and to make the best decision for your roof you need to know the difference.

What Is Underlayment?

Roof underlaymentBefore you know the difference between the two options, you need to understand why your roof needs underlayment. Simply put, the underlayment acts as an added layer of protection to help keep everything Mother Nature related out of your home. It is intended to help shield your home from harsh UV rays and operate as a water barrier for your roof. Underlayment works in two waves. The first period is critical. When all of your old shingles are removed, the underlayment is rolled on to protect the exposed roof from elements until the new shingles can be applied. The second period is after the new shingles have been applied. The underlayment continues to act as another layer of protection. Now that you know the basics, take a look at the features that set felt and synthetic underlayment apart.

What's The Deal With Traditional Felt?

Traditional felt, also known as tarpaper, has been used on roofs for over a century. While it was seen as the standard for years, it is starting to be used less and less on today's homes. The asphalt or bitumen component creates a waterproofing quality that helps shield the home, and while this component may be the most affordable option, it isn't without its downfalls. Traditional felt is permeable, allowing moisture vapor to transfer over time. Its water resistance is only temporary, and leaves it vulnerable to tearing. Contractors must be careful when walking across traditional felt for this reason.

What's The Deal With Synthetic Underlayment?

Synthetic underlayment is where technology meets traditional felt. Created from a woven polypropylene fabric, synthetic underlayment provides the much-needed strength to protect the home through the toughest weather conditions. It offers great protection from the sun's UV rays (typically up to 2 - 4 months of direct exposure) and provides a water resistive coating. Homeowners also benefit from the underlayment's great tear resistance, which means it is not easily ripped by installers treading on its surface or UV breakdown. It may cost a little more than traditional felt, the long-lasting and great protection of synthetic underlayment, especially in the unfortunate event of a storm or if debris detaches a shingle, generally equals to greater savings in the long run.

Have heavy snow or ice buildup on your roof in winter?  You may need more than just underlayment!

ice and water shield or dam or barrierThere is a third type of roof underlayment that is specifically designed for climates where neither roof shingles nor traditional underlayment offer enough protection from leakage.  This self-adhesive membrane-like cover is called ice and water shield.  Available from a number of manufacturers, this product is designed to be installed along the bottom "gutter edge" of the roof directly onto the wood roof deck. 

An ice and water shield is a totally impermeable membrane that prevents leakage through the roof in the event of an ice dam.  Depending on the slope of the roof, this product could be installed to cover the bottom 6 feet of the roof or, with a very low slope, cover the entire roof.   Each layer both adheres to the roof and also to the next layer, creating a continuous shield. 

One of the best features of this type of waterproofing shield is that it is self-sealing around roofing nails, plus it can be used to bolster flashing around chimneys and other vents.  (It is not meant to be exposed to the sun for a long period of time, so it should be covered with a standard underlayment and/or shingles.)

What's Under Your Roof?

Now that it is time to replace your roof, don't hesitate to communicate with your contractor to find out ALL of the components that make up your roof — not just the shingles. Keep in mind though, underlayment is just one of the four main components of a complete roofing system. So create an open dialog so you can understand every component of your new roof. For more information on underlayment, or the entire roofing system, contact Sherriff-Goslin for a FREE roof inspection and one of our local representatives will be happy to go over all the available options for your home.