The roof sheathing is installed and a roof covering permanent or suitable reliable temporary roof waterproof.
Roof dry in.
Drying in for better lack of a term is making a house impervious to the rain or short for dry inside.
For slopes lower than 4 the overlap is 18 inches half the width of the roll.
March 7 2020.
In short drying in a structure means that the roof has been protected with at least a layer of felt a product like tyvek housewrap has been installed along with all the windows and doors.
What is dry in.
Roof dry in flashing and underlayment.