One of the most confusing aspects of homebuilding can be the
rough opening for an overhead garage door. It is one of the
most frequent questions I am asked.
The rough opening for a garage door, simply put, is the
actual size of the door itself. For example, if the garage
door is a 7’0″ x 16’0″, then that is the size the rough
opening should be framed to. This is also what the opening
in the foundation should be. The studs and cripples will
then stop right at the edge of the foundation.
The foundation usually drops 8″ to allow the concrete floor
to be poured over the top of it. This has to be accounted
for when figuring the length of the cripples to get the
right height of the overhead door header. Normally the
floor is poured 3″ below the top of the foundation wall. If
the overhead door is 7′ then 4 and 1/2″ is subtracted from
that height. This is the 3″ drop and 1 1/2″ for the bottom
plate. Your total cripple length would be 6′ 7 1/2″.
Once the floor is poured, the door jambs can be installed.
The width of these jamb pieces vary with the size of the
wall and what the wall is finished with (brick, siding,
dryvit, etc). The header piece is installed first, then the
two side pieces. These go from the header to the finished
concrete floor. Once the jambs are in the door can be
installed. With the door installed the door stops are then
put on either with or without weatherstripping.
If you know the door size of your overhead door, you know
the rough opening. From there its determining where to start
and stop your framing.
(c) Mike Merisko http://www.sawkerfs.com