Did the roofer obtain a permit? All jurisdictions, with the exception of county, require a permit. Ask for proof of permit. Is the roofer licensed? Ask for a copy of his license. Is the roofer insured? Ask for a copy of this general liability insurance and his Workers Comp insurance.
Is the drip edge flashing installed properly? The current building code requires a metal drip edge flashing at the edge of the roof. This flashing must extend 2″ up the decking. Some roofers are still using 1-1/2″ flashing. The flashing must be fastened with nails no more 12″ apart. Most roofers space these nails 3′ – 5′ apart. The underlayment needs to be on top of this flashing at the eaves and under the flashing at the rake. If you have gutters, they must tuck under the drip edge flashing.
Is the roof installed properly? Manufacturer’s installation instructions must be followed. This is a code requirement. The first thing a roofer must do is install a starter strip. These can be bought or made at the jobsite. They must be installed with the adhesive strip close to the edge of the roof. If this is not done properly, the first course of shingles will have no protection from wind uplift. Are the shingles properly nailed? This is normally just below the adhesive strip. A few manufacturers place a line where the fasteners belong. Shingles require 4 nails – 1 at each end and 1 at each tab cutout. Is there proper exposure at the shingles. Different shingles require different exposures. The most common exposure is 5″ and exposures of 5-5/8″ and 6″ are often seen. Very few roofers follow all of the installation requirements.
Ask for a copy of the warranty and the manufacturer’s installation instructions, and read them carefully. Make sure that your installation complies with the manufacturer’s instructions. Watch the installation and take plenty of photos. Get on the roof, if need be and you feel comfortable doing it, to verify the installation.
If everything is done properly, then you may pay the roofer.