The underlayment is the layer between the roofing shingles and the roof deck. Its main purpose is to act as a waterproof barrier and to protect the roof deck from damage. This is why the quality of the underlayment has an impact on how long the roof lasts and on how well it protects your interior from the weather.
A roof replacement project is an expensive investment in your home and should be given a good deal of consideration. To prepare yourself for it, and to make it as smooth as possible, Exterior Source suggests these tips: