Flashing helps direct the flow of water around openings. Since water can seep into your home’s walls, deteriorating building materials, causing structural damage, and creating moisture and mold problems, it is very important to properly install flashing when constructing a new house or altering the exterior of a house. Flashing is used beneath the first course above ground level in a masonry building, above all wood trim on shelves, doors, and windows, where exterior stairs and decks attach to the house, and around any features in the roof structure. Below are some of the common flashing details on residential roofs. DIY Network.

The Tyvek is up. Don and his crew from Potter’s Roofing nail the roof flashing into place, tucking it under the Tyvek.

When Ranserve took out the interior drywall, Steven stood upstairs, in the center of the house, turning 360 degrees — and daylight intruded into the house through gaps between the original cedar siding and the top of the lower roof. The flashing and Tyvek begin to seal those gaps. The house won’t be airtight when Ranserve is done, but a lot less heating and air conditioning will escape, helping the house qualify for the Austin Energy Green Building program.