How to Install Asphalt Shingles

If your roof is missing shingles or if the shingles are cracked, broken or even just curling at the edges, you should consider installing new shingles. Replacing roofing is not a job for everybody - it's a heavy, tedious job and requires you to work off ladders and right up on the roof itself. However, shingling is not overly complicated, and it is a job homeowners can do themselves (or preferably with the help of two or three friends).

Shingles are sold in "squares" that cover an area of 100 square feet. An individual shingle is 36 inches long and 12 inches wide with tabs cut every 12 inches halfway through the width of each shingle. At the base of the tabs is a line of soft tar that will soften in the heat and help seal the shingles to the roof.

Calculating needed supplies

  1. Measure the length and width of the roof sections to calculate the square footage to be covered, then add 10 percent for wastage, dividing the result by 100 (to determine the number of squares you will need).

  2. Use the square footage of the roof to determine the amount of roofing felt needed to cover the entire roof (under the shingles) and the amount of waterproof membrane needed to cover the lower edge of the roof and protect it from moisture.

  3. Calculate the amount of roofing nails you will need using the fact that each square of shingles will require approximately 2 1/2 pounds of roofing nails (use galvanized roofing nails with a 3/-8 or 1/2-inch head).

Preparing the roof

  1. Remove the old shingles using a square-tipped spade or, better yet, a roofing shovel. (A square-ended shovel with teeth can get under nail heads and pull them out).

  2. Check that the roofing material (plywood or strand board) is in good shape (no rotten spots), and is nailed down firmly.

  3. Replace any rotted sections and add nails if necessary to hold the wood solidly in place.

Shingling the roof

  1. Start at the lower left-hand corner (as you face the roof) and install the "starter course." You do this by removing the tabs from the shingles used in this starter course and nailing these "half shingles"' with the cut side facing out. Cut 6 inches from the length of the very first shingle placed in the lower left-hand corner and then butt the rest of the shingles in the row all along the lower edge of the roof. Overlap the roof edge by about a 1/2 inch.

  2. Begin installing the first row of shingles again at the lower left-hand corner. Start with a full shingle in the corner (again overlapping the roof side and edge by about a 1/2 inch) right over the starter course. Snap a chalk line at the top of this shingle as a guide for when you install the rest of the rest of the row.

  3. Move on to the first shingle in the second row by cutting 6 inches off the length and installing it over the starter shingle in the first row. Line up the bottom edge of this shingle with the top of the tabs in the first row of shingles.

  4. Continue installing shingles at the left edge of the roof, cutting 6 inches off the length of the first shingle in every other row. By installing shingles up before moving along the roof, you eliminate moving across the width of the roof with each row. The first shingle in the seventh row will be a full shingle.

  5. Start working your way across the roof after installing the first shingle six rows up. Butt the shingles against each other and fasten the shingles with four nails each. Trim the shingles at the far side of the roof so they overlap the roof edge by the same 1/2 inch as on the starting side.

  6. Continue this process until you reach the top of the roof where you will trim the shingles to fit along the ridgeline. Follow the same process on the other side of the roof, starting at the lower left-hand side and working up and out until you reach the top. Overlap the shingles in the top row of the second side to cover the ridge and nail them in place.


  • Working on the roof can be dangerous. Secure your ladder at the top and bottom, and always let someone know you are working on the roof.
  • Shingles are heavy. Don't try to be a hero and climb with a big load. It may take a little longer but it's safer to make two trips.
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