Like an unwanted spider edging across the wall, a hairline crack appears, seemingly overnight, before creeping across the ceiling or downward to a door or window frame. Cracks can be superficial nuisances that occur soon after the completion of a new home, or they can be the result of a more serious problem. With modern drywall taping techniques, you can repair most cracks, but if you don't address the cause of the cracks, they can appear again -- in the same spots.
Various issues can cause soil movement, which then results in foundation settling and cracks in the walls and ceilings. If the builder did not adequately compact the soil beneath the poured basement or around the basement walls, shifting may occur.
Improper yard grade can add to the problem. The soil should slope downward, away from the foundation. When it doesn't, water can pool next to the foundation, seeping down along the walls. When the soil dries, it can pull away from the wall, forming a gap. Subsequent saturation intensifies ground swell next to the foundation, putting undue pressure on the basement walls.
Proper drainage, guttering and downspouts and not planting next to the foundation can reduce moisture-related cracking.
Wall construction isn't rocket science, but a few mistakes can increase the risk of cracking. If the stud wall is not aligned, the drywall panel can bend slightly during installation, creating a weak spot that may crack. Incorrect wall framing for windows and doors can contribute to cracks that extend vertically from the window or door frame.
Climate Control Issues
Things expand when hot and contract when cold, and walls are no exception. In a home that's climate controlled, where temperatures do not vary greatly, wall studs and drywall panels are less likely to suffer from temperature-related cracks.
New Home Cracks
Finding hairline cracks in new home walls and ceilings is not unusual, especially if the builder constructs the home quickly. A new home contains a number of moisture sources, which can create high humidity levels indoors. When the humidity drops, the drywall can contract and crack. These cracks are usually minimal and easily repaired.
Newly poured concrete takes a while to completely cure. While it's drying out over a period of weeks, it releases moisture into the air. Another source of high humidity in the home comes from joint compound and paint. Used to finish out drywall, joint compound releases moisture into the air as it dries. Paint also releases some moisture.
Leaving windows and doors open during construction can help reduce indoor humidity, and running an air conditioner or a heater after the finish is in place will also help.
Tape looks a lot like a crack, but it's not. The drywall contractor applies paper tape over wet joint compound when he's finishing out the drywall panels. Sometimes, there is insufficient compound to seal the tape in place, and the edge of the tape can come loose, making it look like the wall has a crack. Retaping the joint will fix the problem.