Traditional three-tab asphalt shingles contain cutouts on their exposed portions that give each shingle the appearance of three separate pieces when installed. Architectural, or dimensional, shingles, on the other hand, include an additional layer of asphalt in their lower portions that creates a thicker, three-dimensional appearance and provides an extra layer of waterproofing. Architectural shingles add interest to a roof, but only proper installation will ensure a durable, waterproof surface.
Choose shingles that complement your home's architectural style as well as its specific waterproofing needs. Architectural shingles are manufactured to mimic a wide variety of materials including wood, slate and tile, with profiles to complement nearly every architectural style, from scalloped to squared edges. Color choices are even more varied. Check the literature of your chosen product to make sure it is suited for the slope of your roof. Generally, architectural shingles are not recommended for low-sloped roofs, but every product has a its own requirement.
Preparing the Roof
Remove old shingles, if necessary, with a pitchfork starting at the peak of the roof working your way down. Remove any remaining nails. Check the roof deck for stability and rot. Cut out any rotted sections with a circular saw and replace them with new plywood of equal depth to the existing deck. Remove all nails, flashing, underlayment and drip cap left over from the old roof and replace with new materials.
Take precautions not to jeopardize your roof's stability with improper nailing. Select roofing nails of the proper length according to your shingles' specifications. Nails may need to be driven a minimum length into the roof decking. Drive nails through shingles in the recommended quantities and locations. Steeply pitched roofs may require additional nails per shingle. Check that nails are driven straight and not at an angle and that each nail's head is flush with the shingle's surface.
Installing the Starter Course
Starting at the lower left-hand corner of the roof, install a starter strip along the bottom of the roof. A starter strip may consist of a single, rolled strip or a bundle of specialized shingles depending upon your choice of materials. The starter course should hang over both the bottom and left and right edges of the roof. Check your product's specs for the exact overhang amount.
Installing Additional Courses
Begin your first course with a full shingle at the lower left-hand corner of the roof and work your way to the right. Allow the right edge of each course to overhang the right edge of the roof. On your second through fourth courses, cut successively more off of the left edge of the first shingle. Check you product's instructions for how much to cut off of each course. Additionally, many architectural shingles are marked or notched where cuts should be made. Begin your fifth course with a full shingle. Continue this pattern as you work your way up the roof, cutting course six the same width as course two.
Finishing the Roof
Trim the top course to be level with the roof's peek on both sides. Snap a chalk line along the right edge of the roof where you want the overhang to end. Cut along the chalk line with a utility knife. Install ridge cap over the roof's peek. Your chosen product line will include specialized shingles for this purpose. Wrap them over the roof's peek and nail them into place according to the product's instructions.