In new construction most doors are hung after the floors are
installed. This allows flooring contractors (tile, hardwood,
vinyl, laminate) to lay their flooring products without
making tricky cuts around door jambs. It also makes for a
neat and clean door installation. Exceptions to this are
carpeted floors. Doors are hung before the carpeting is
laid. When doors are hung in carpeted areas, its a good idea
to shim them up 1/2", putting a shim under each jamb leg.
This eliminates the need to cut the doors down after the
carpet is installed.

For a 6' 8" high door (80 inches) I like to frame my rough
opening heighth at 82 3/4". This allows room for all the
situations mentioned above. If your header material is a
double 2x12, holding it to the top plate will give you that
heighth.

Rough openings for door widths are pretty much standard. The
rough opening width is 2 inches wider than the door itself.
this allows room for the door jambs which are usually 3/4"
thick. This gives you approximately 1/2" of play and shim
room when installing a prehung door. For a 36" door (3' 0")
the rough openig width would be 38". Here are the most
common door sizes and their rough openings.

Door Size Rough Opening Size

2' 0" x 6'8" -26" x 82 3/4"
2' 2" x 6'8" -28" x 82 3/4"
2' 4" x 6'8" -30" x 82 3/4"
2' 6" x 6'8" -32" x 82 3/4"
2' 8" x 6'8" -34" x 82 3/4"
2' 10"x 6'8" -36" x 82 3/4"
3' 0" x 6'8" -38" x 82 3/4"

To figure the rough opening for double doors or french
doors, take the door size times 2 and add 2". The most
common sizes for exterior doors are the 2'8" and the 3'0"
doors. The 2'8" is usually used for the back door and the
access door from the garage. That size door for exterior use
is being used less these days because of the size of
appliances and furniture. Exterior doors with sidelights and
sliding patio doors rough openings vary from manufacturer to
manufacturer. These should be verified and gotten from the
supplier.

Getting the rough openings right the first time keeps the
sawzall in its carrying case and having to change the
opening after the walls are drywalled and painted.

To learn more about installing doors, check the archives of
this blog or go to www.sawkerfs.com

Mike Merisko (c) 2006
www.sawkerfs.com