Before you purchase a patio door frame, you need to be certain about the measurements you need to fit your space. The last thing you want to do is to purchase a patio door and have it not fit. Most patio doors feature standard measurements but you will also run into doors that are made for custom doorways. In order to purchase a correctly-sized patio door, you’ll want to take several measurements:
Inner Vertical Frame: Measure from the top of the subfloor to the top of the inside portion of the frame.
Inner Horizontal Frame: Measure the length you desire between two studs in the wall while keeping the tape measure level. Make sure you add two inches to account for the frame.
Two Vertical Measurements: Make a vertical measurement on either side of the door and make sure that the figures are the same.
Two Horizontal Measurements: Measure the length at the bottom and the top and ensure that the two numbers match.