With doors being the second largest holes in a buildings exterior, they will require both concealed and in some cases exposed flashing as well. Without flashing the doors, the wall cavity could become exposed to weather and moisture. Different door manufacturers may have different guidelines to follow in terms of how to install their doors and maintain warranty, but the general premise is the same for all. The following is the general procedure for a standard man or sliding door being installed on a wall assembly with house wrap.
The rough opening is prepared and the house wrap is cut to suit. This often consists of cutting in a manner that will allow the house wrap to wrap the jambs, sill, and head in preparation for the window. The housewrap is then wrapped inward and attached to the rough jambs and sill.
Next self-adhering asphalt or butyl based flashing tape will be added, which will need a spray adhesive boost in cold weather. Also, butyl tape can be easier to mold and place. This tape limits moisture penetration through the rough jambs and provides a solid, smooth substrate for the door installation.
Sometimes it is available with the door or a type of tape is specifically recommended by the door manufacturer. The door is then placed, leveled, shimmed, and the jambs fastened to the rough opening. With the top of the door being the most vulnerable moisture penetrable location, ‘pan-flasing’ or a drip cap is often placed, especially if the door casing protrudes from the face of the wall. This cap my come with the door or can be made with aluminum coil stock.