There are various factors to consider when choosing a fire door and preparing the opening needed to install it.
The Open Space or Open Passage
Also known as the clear opening, this is the space left for passage when the door is installed and open. It is the usable space that will be available to the user.
The Construction Site
It is the opening needed to install the door, or the opening that has been cut into the wall to install the door frame.
Total Measurement or Total Opening
It is slightly wider than the opening in the wall, since it includes the frame’s overlap. In other words, it is measured from the outside of the overlap.
The opening size and overall dimensions vary depending on the frame’s design or model. Thus, two doors with the same clear opening width may require two different opening sizes and will also have different overall dimensions.
Below are some diagrams showing how to adjust the measurements depending on whether the door frame is a standard Z-shaped frame or a U-shaped tunnel frame.
DOOR WITH Z-SHAPED FRAME
DOOR WITH A U-SHAPED FRAME
