To create a proper rough opening in a door, one must understands how the dimensions of a door relate to the dimensions of the wall opening. If the rough opening in a wall is too small for the intended door and door frame, the door wont fit into the opening. If, however, the rough opening in the wall is too large for the door and door frame, the door will not be able to sit against the studs in the framing structure.
In either case, you must calculate the rough opening dimensions prior to cut openings in the wall studs. The formula for calculating the dimensions of the rough opening is to take the nominal dimension of the door and add two inches to the width of the door to allow for the door frame, the hinges, and shims; the height of the door will be increased by two and a half inches to allow for a plumb door within the opening. Not all rough opening dimensions will be the same, however.
How to Measure a Door Opening
Different type of rooms require different rough opening widths. For instance, the rough opening in a closet may be narrow; a person only needs to reach into the closet. A bathroom, though, may require a wider rough opening to allow for an individual to move a laundry basket through the doorway.
Additionally, bedrooms often require wider openings than closets due to the potential for bedroom furnitures to interfere with the doors movement. One can use a chart to ensure each type of room has the correct dimensions for its opening, thus avoiding having to calculate the rough opening dimensions for each door. The structural element of a wall opening include a number of specific studs.
King studs extend from the studs to the foundation and is responsible for the structural weight of the wall. Jack studs sit against the king studs and are used to support the header. The header is the horizontal board that will support the weight of the wall above the door opening.
Cripple studs are installed between the header and the top of the wall studs. The header may sag over time if the studs are not included; if the header sags, the drywall above the door may crack. The width of the header in the opening is determined by the width of the doorway and the weight of the structure above the doorway.
If the doorway is narrow and the wall structure is an interior wall, for instance, a doubled two-by-six is the minimum requirement for the header beam. However, if the doorway opening is wide, or if the doorway includes an exterior wall, a deeper beam may be required for the header. In these situations, it is always best to purchase a header that is one size larger then is required; it is more cost effective to replace a sagging header than to install the header at the time of construction.
Additionally, one must consider the thickness of the studs within the wall when purchasing the door jamb. For instance, if the studs are two-by-four studs, the studs will include drywall and the jambs will be four and a half inches deep. If the studs are two-by-six studs, however, the studs will include drywall and the jambs will be six and a half inches deep.
If you purchase the jambs with a different depth than the studs will be constructed with, there will be additional work that must be performed to ensure the jamb fits within the wall. One can choose between using a pre-hung door and a slab-only door. A pre-hung door includes the door and it’s frame, and is useful for reducing the labor needed to install the door.
A slab-only door, in contrast, is only the door portion of the door and require the installer to attach the frame and plane the door. A pre-hung door requires cutting a rough opening of larger dimensions than a slab-only door, though. Finally, accessibility and safety rules will impact the sizing of the door.
For instance, a thirty-six inch rough opening is required in order to allow for a thirty-two inch clear width for accessibility by those who use wheel chairs or other mobility aid. You should of consider the room size when planning the layout. One should of checked the measurements twice to avoid any mistakes.
Its important to make sure the door is actualy sized correct.
