Lap marks are those ugly stripes caused by uneven layers of paint buildup. They occur when you roll over paint that’s already partly dry. (In warm, dry conditions, latex paint can begin to stiffen in less than a minute!) The key to avoiding lap marks when doing DIY wall painting is to maintain a “wet edge,” so each stroke of your roller overlaps the previous stroke before the paint can begin to dry.
Good contracts include descriptions of prep work and repairs; paint specs by brand name, type, color and product number; the number of coats; and a full description of the work, including frequently omitted items such as cabinet interiors and shutters. Minimize delays by specifying that, weather permitting, work will be continuous. Get a payment schedule that minimizes the down payment — the more payment you can withhold until the end, the more leverage you'll have to get the job done well and per your specifications. Insist that contractors provide proof that they carry both general liability and workers' compensation coverage.