Asphalt shingle roofs should always be installed over solid roof sheathing. The nails that you use to fasten the asphalt shingles to the roof should be 11 or 12 gauge hot-dipped galvanized or aluminum roofing nails, the heads should be at least 3/8 inch in diameter, the nails should be barbed, deformed shanked, or ring shanked, and should be 1 to 2 inches long depending on the situation. See recommended lengths below:
When reroofing with asphalt shingles, you should use nails that will penetrate at least 3/4 inch into the sheathing. You can make sure your nails are long enough by checking underneath the sheathing after you nail into it. You should allow for about 2 1/2 pounds of nails per square.
When nailing shingles across a roof you should start nailing at the end closest to the shingle you just laid. This will prevent buckling. You should drive the nails straight so that they don’t damage the shingle and the nail head lays flat on the shingle. You should never drive nails into knots, cracks, or joints in the sheathing. If you must remove a nail you need to seal the hole with roof cement or replace the shingle entirely. Nails should be driven in just below the factory-applied self-sealing adhesive strip. Generally you should use at least a minimum of 4 nails per shingle but many building departments, especially in high wind areas are requiring 6 nails per shingle. When installing a 5-inch exposure shingle you should drive the nails in along a line that is 5 5/8″ above the butt edge of the shingle. Never drive the nails in too high (high nail) as you need to ensure the nail also penetrate the shingle underneath. See video below:
Usually when nailing materials into sheathing you try to avoid nailing in a straight line to avoid splitting the wood however in this case nail placement is extremely important. If you nail too high you miss the shingle underneath, if you nail too low your nail is exposed (shiner). You should always stagger nail when you can but in the case of nailing asphalt shingles you MUST nail them in a straight line. You should drive the two outermost nails 1 inch from each end of the shingle. The innermost nails should be driven into the shingle just above the cutouts.
Shingles with no cutouts such as architectural shingles also require at least 4 nails. When you are laying the shingle with 5 inch exposure, you must drive the nails in 5 5/8 inch above the butt edge. The end nails should be nailed 1 inch from the edges and the 2 innermost nails should be driven in 12 inches from the edge of each side.
Many building departments require six nails per shingle. Especially in high wind and hurricane areas such as Florida. See video below to learn how to install 6 nails per shingle.