Like drug and alcohol use on the job site, theft is a no-brainer. But theft from the job site might be a little trickier to spot than a kid in a candy store with bulging pockets. Instead, your contractor might over-order supplies and then simply truck away the excess when that part of your job is done. Who'd ever know that a contractor was using "extra" supplies to remodel his own bathroom? Or using your extra supplies on a second job site and pocketing the funds from the other homeowners?
If you suspect this kind of theft, compare the Bill of Materials list included in your contract with receipts for the materials your contractor actually orders. In extreme cases, you might need to monitor the materials delivered to your site [source: HomeAdditionPlus.com]. But once you've reached the point of counting boards, you'll wish you'd fired your contractor long ago.