After refining your shortlist to a maximum of two roofers, ask each of them to come and inspect your home and give an estimate. The way the contractor receives and reacts to your inquiry will tell you a lot regarding his professionalism. Make a note of who he sends across to evaluate the job requirements and whether he is genuinely competent or just someone who will pass on the information to his boss who will in turn revert to you.
Ask him for a detailed estimate after taking into account all your expectations. Make sure that it is in writing and that everything is detailed upfront without any charges hidden in the fine print. All roofers give the estimate free of charge so do not entertain those who try to get an upfront fee for the inspection and estimate.
Ask specifically whether he is covered under the workmen’s compensation and has a minimum liability insurance of $1 million, and ask for copies of his trade license and the insurance policy. Since the job is of a very short duration, insist on giving the payment in two installments; one for the materials and the second on completion of the job to your satisfaction. Insist on a warranty that will generally have two components; one that covers the shingle and the other the workmanship.
The best quality shingles will have a manufacturer’s warranty of 50 years but be careful to verify under what conditions the warranty will not apply; a common example is when the shingles are laid over an existing layer. The second warranty will cover the workmanship, including leaks, failure of flashing, and other defects arising out of incorrect or sloppy workmanship.