If in a rare situation, your roof fails due to defective shingles, the reimbursement for the shingles’ cost will still not make much impact on the overall cost of repairing the roof. Labor is the most expensive part of a roof repair and not the shingles. More than 75% of the cost is based on the materials, such as roofing cement, underlayment, screws or nails, flashing, and labor. A warranty covering only the replacement shingles and not the labor may only be a small portion of the huge expense of replacing or repairing the roof.