There should be a 2mm or 3mm gap between the door and the frame on both sides and the top. If you do need to cut the door down to size, keep in mind that you need to cut all four sides of the door equally whenever possible to retain an accurate shape or pattern if the door is panelled.
It should also be consistent — the same size from top to bottom on all three sides of the door. A gap of around 1/8th of an inch is recommended for standard doors to keep the elements out, protect the paint on the trim, and ensure that the door closes and opens smoothly.
Framing rough opening sizes are really quite simple. Just add 2″ to the width of the actual door size. You should add 2-1/2″ to the height of the actual door. This will give you room to space the door frame off of the sub-floor.
The reveal is the small gap between the edge of the door jamb (i.e., the frame from which the door is hinged and where the latch engages) and the trim. To outline it, use a combination square to mark a consistent reveal of 1/8 to 1/4 inch around the entire door frame.
the gap between the underside of the door and unfinished floor should be between 10mm and 22mm, with the ventilation requirements for the building taken into account when determining the gap beneath internal doors.
Hinge Margin: Space between the door panel and door frame on the hinge side of the door. A standard hinge margin is 1/16", but can vary based upon the hinges used. Strike Margin: Space between the door panel and door frame on the strike, or handle, side of the door. The standard strike margin is 5/32".
Internal Door Undercuts
As a guide the average undercut of your door should be between 8mm and 10mm, that's around ⅝ inch to ¾ inch from the bottom of the frame.
Margins (sometimes also called “rebates”) are the spaces between the door and the door frame. These are often important if you're looking at issues with your hinge jamb. Again, these spaces can be broken down into specific types: the hinge margin, strike margin, top (header) margin, and bottom (sweep) margin.
Recommended clearance: Between door and jamb leave 3mm of space.
The door frame manufacturer will then add their standard clearances to these dimensions to give what is called the Reveal Size. The Reveal size is the actual opening inside the frame that the doors will sit in. So in the case of a 2040 x 920mm door, the standard reveal size would be 2055 x 924mm.
Standard Rough Opening Sizes
The way this is determined is, take the desired pre-hung door size (door size not including the frame) and simply add 2" to the width and roughly 2.5" to the height. That's it. This extra 2" gives room for the door's frame as well as a little extra play for getting the door perfect.
Door widths vary, but an easy way to size the rough opening is to use the door width plus 5 in. as the distance between the king studs. There are three simple rules to framing rough openings efficiently: Minimize layout marks; maintain a simple, consistent nailing pattern; and avoid toenailing when possible.
Use a level when you are working and make sure that the "reveal," or horizontal gap between the head jamb and top of the door, is between 1/8 and 3/16 inches wide.
As a general rule of thumb we say 2 to 6 inches between frames is a good starting point for consistent spacing to make things look balanced in a grouping of pictures. However, the physical characteristics of the frame can have an influence on how much space you put in between them.
If light or drafts are coming around your door since it was installed, it is not level in the frame. You will notice this as soon as the door is first installed, or if you move into a new home and notice this problem, the door was most likely not installed properly when it was put in.
There should be a 2mm or 3mm gap between the door and the frame on both sides and the top. If you do need to cut the door down to size, keep in mind that you need to cut all four sides of the door equally whenever possible to retain an accurate shape or pattern if the door is panelled.
Ideally, there should be a gap of about 1/2 inch between the bottom of the door and the floor to allow for expansion and contraction due to temperature changes. Additionally, side clearances should be approximately 1/8 inch on both sides to ensure smooth operation.
Readjust, Plane, or Sand Down the Door Jambs
Replacing the shims with thinner shims may give you more room to expand the door frame. If you only need a little bit more space, you may be able to sand or plane down the door jambs without removing them.
A well fitted door should have a 2mm gap on either side and at the top. The gap at the bottom will depend on the thickness of your flooring/carpet. Plane the door as required, using an electric plane will help you get an even finish, and sand for a smooth finish.
Check clearances between door and frame. It should be 3mm to the sides and top. There should be adequate clearance to the floor. Fix the remaining hinge screws to the door and frame.
What are frame gaps? To keep the subtitles in sync with the audio, gaps should be minor and are often expressed in frames (we refer to them as "frame gaps"). Frames are the static images that make up a video. Usually 24 or sometimes 30 frames follow each other every second to create a moving image.
NFPA 80 currently allows a maximum bottom gap of 3/4 in.
In general, the gap beneath an interior door will be between three-quarters of an inch and half an inch. This width depends largely on the type of flooring, as door frames are generally installed when the floor is unfinished. A standard door can have varying levels of clearance over different flooring types.
It is definitely a matter of personal taste, but as the one holding the big picture vision, you will need to keep a few things in mind. Too many different shades of natural wood in the home might clash. An oak floor might not look great with a door in the shade of maple.