Some time right before the drywall is hung in your new home, check to see if there is a gap between the headers and the cripples they rest on.
A “GAP” will occur as the header(usually 2 2×12’s nailed together)begins to shrink due to its drying. The cripple acts as the support for the header and the header acts as the support for the load above it.
The gap between the header and cripple can be anywhere from a 1/16″ to 1/4″ or more.
Shimming of these gaps is to prevent the header from settling into the gap.
If you’ve been to an existing home and the homeowner complains that a couple of the windows open hard or don’t close easily or the top of a door rubs against its frame, this could be from the header settling.
The settling may also cause drywall cracks at the top corners of all interior and exterior doors along with the windows of your new home.
We use cedar shims that are sold by the bundle and we drive them in until they break.