Big difference. Roll roofing is a lightweight, budget roofing material, available in 36” wide rolls, containing 100 square feet (also called a “square” by roofers) per roll. Average lifespan is about 6 to 10 years, and it is usually face-nailed in place, which means that the nail heads are exposed and visible on top of the roofing. The combination of being inexpensive to buy and simple to install makes it a popular choice for sheds, porches, and barns.
But every nailhead is a future leak. A spot of mastic at each nail head, like in the photo above, postpones the problem for awhile. A more waterproof installation method uses a strip of mastic to secure the bottom of each new roofing lap over the previous one, along with spots of mastic over the first row of nails. However, the short lifespan of the material makes it a poor choice for re-roofing a house, and we rarely see it used for residences.
