This is garage addition we did for a family in Bellingham, Massachusetts. As you can tell the frame is complete and you can see Mike up on the roof applying ice-and-water barrier to the edge of the plywood roof in preparation for asphalt roofing shingles. Ice-and-water acts as a protective barrier for… you guessed it, ice and water. This is especially important here in New England. What can happen during cold winters is that ice can melt from higher areas of the roof and the water will travel down the roof. This water will often refreeze and cause ice-dams on the lower edges of the roof planes(eaves). This barrier will help to protect the roof in case the ice dams are able to penetrate below the shingles. A responsible roofing contractor in the North East will ALWAYS use ice-and-water barrier on the eaves and valleys to add extra weather protection to your home.