Preparation

• 1). Wrap the addition in a house wrap, such as Tyvek. Apply in overlapping courses starting from the base of the addition and working your way up. Overlap adjacent pieces by at least a wall stud's distance and overlap one course about 12 inches over the course below it. You can cut house wrap with a utility knife. Fasten the product to studs with siding nails fitted with plastic caps. Cover seams with seam tape.
  
  
• 2). Make a story pole. Take a long, thin strip of wood and set it against your existing siding. Use a pencil to mark the base of each course of shingles. By referring directly to these marks you can maintain consistency when installing new material.
  
  
• 3). Fasten furring strips to the house. Cut 1 inch by 4 inch boards to fit horizontally across the exterior walls. Refer to your story pole and fasten these furring strips above the exposed portion of each shingle course. Each shingle will be nailed in the area where the shingle course above will cover. This hides the nails and increases the overall water-resistance.
  
  

Installing the Shingles

• 1). Fasten your first shingle course. Refer to your story pole, start at one side of the addition and work your way across. Use a level and chalk line to snap a line marking the base of the shingle course. Affix each shingle with 2 corrosion-resistant nails driven into the furring strip. The nails should be 3/4 inch from each edge of the shingle and about 1 inch above exposure line. Shingles are often tapered in thickness; make sure to install them with the thicker end pointed down.
  
  
• 2). Leave about 1/8 inch between each shingle to allow for expansion. On your first course, install 2 layers of shingles, with the base line of the second layer falling about 1/2 inch below that of the first. Stagger the seams between the shingle layers. The lowest shingle course is the most susceptible to water damage and this double layer will increase water-resistance.
  
  
• 3). Fasten your second course of shingles. Refer to the story pole to determine where the base of these shingles will fall. Stagger seams between shingle courses to increase water-resistance. Trim shingles to fit at the ends by slicing them with a sharp utility knife.
  
  
• 4). Lace the corners. On the outside corners where 2 shingles meet, trim one shingle flush with the edge of the house and the adjoining shingle flush with the face of the shingle it meets. Alternate this pattern from one shingle course to the next to increase water-resistance.