Remove the old shingles from the roof before installing the three-dimensional shingles. Inspect the roof sheathing ensuring it isn't rotted or in need of repair. Once any needed sheathing repairs are made, lay down the drip edge along the edges of the roof. This metal edging piece helps the water run off the roof into the eaves. Staple roofing felt to the sheathing before installing the architectural shingles. The felt should overlap at seams for better protection.
A starter row of three-dimensional shingles is needed that fully protects roof’s edge from water and ice. The regular shingles have gaps that allow ice and water through. On the subsequent shingle rows, overlapping protects the roof from those gaps, but the first row doesn't have anything to overlap, which is why the starter row is necessary. These special shingles are nailed in place with one-eighth inch hanging over the roof’s edge for extra protection.
Once the starter row is in place, install the architectural shingles to the roof. Start along the roof’s bottom edge, installing the first row of shingles directly overly the starter row. Review the manufacturer's recommendations for the size of roofing nail for the specific architectural shingles you chose. The added thickness of the shingles means you may need a longer roofing nail than with regular asphalt shingles. On each row, stagger the shingle edges so they don't line up from one row to the next. The staggered shingle edges provide greater protection for the roof underneath.
Trimming the three-dimensional shingles at the ends of most rows is usually needed. When the roof’s peak is reached, install the special ridge cap shingles that go over the peak covering both sides. Those pieces are nailed to the roof as well, providing protection to the peak and directing rain down either side of the roof.