If the shingles on your roof are cracked, peeling and falling apart, chances are that you are in the market for a new roof. If so, roofing felt will be on the list of required materials for your project. To prevent the loss of your hard-earned money, you must first determine what type roofing felt to use. You should consider several different factors before you start.
Function - Roofing felt is an underlayment that functions as a secondary moisture barrier for your roof. According to the University of Massachusetts, felt "will prevent 99% of the moisture problems caused by wind-driven rain and snow." Roofing felt adheres directly on top of the roof deck. The exterior roofing materials---shingles, roof tiles or metal panels---cover the roofing felt. Roofing felt can prevent expensive damage to your home if any portion of the exterior roofing material dislodges during a storm.
Types - There are two types of roofing felt on the market. One type is paper-base roofing felt. Paper-base roofing felt consists of heavy stock paper impregnated with asphalt. The other type roofing felt is fibreglass-base roofing felt. This type felt consists of a fibreglass mesh impregnated with asphalt; it has a higher fire resistance rating than paper-base felt. There are two available weights for both types---#15 and #30. The thicker of the two weights is #30.
Installation - Roofing felt comes in roll form. Installers roll the felt across the roof and secure it to the roof with a hammer and nails, an electric stapler or a hammer tacker used specifically for attaching roofing felt. The roofing felt must lie flat. Any wrinkles in the felt may cause the shingles to buckle or warp, allowing moisture underneath the shingles. Because #15 felt is thinner than #30 felt, it requires more nails or staples to secure it.
Considerations - Do not neglect to determine the required building code for your area. Building codes vary by state and even by city. Contact your local building official to determine the minimum requirements for roofing felt. Otherwise, you may find that you have wasted precious time and money purchasing and installing roofing felt that does not meet code requirements. Consider contacting your insurance agent as well. Some insurance companies offer discounts for using upgraded materials.
Warning - Safety is a concern when determining which roofing felt to use. If you plan to install your new roof yourself, remember that #15 felt is thinner than #30 felt. It tears more easily if you walk on it---especially if not thoroughly secured to the roof. This makes the roof slippery and could result in a fall. It is crucial to exercise care regardless of which weight you install.