Check the door fit. Ideally, there should be a gap of about 1/8 inch at the top and along each side, and about 3/8 inch at the bottom. Use cardboard spacers or folded matchbooks (four thicknesses equals about 1/16 inch) along with shims underneath to maintain the spacing.
The standard size of a door jamb is 4 9/16 inches wide by 6 9/16 inches tall.
Casing should sit back from the face of the jamb by 1/8 inch to ¼ inch. This is called a reveal, and carpenters mark it all around the jamb with a sharp pencil and combination square.
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.
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.
Door jamb versus door frame
A door jamb is an individual section of a door frame. Two side jambs make up the vertical components of the door frame and the head jamb is the top horizontal component. Together, the jambs (along with mullion) comprise the door frame.
In most applications, the door undercut would need to be 1.5 inches or greater to allow enough air to pass. There are some through-the-door alternatives that can be effective. Consider installing a transfer grille in the door or employing another return air pathway method, such as transfer grilles or jump ducts.
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. if you are in doubt, shave or cut off a little and if it's not enough, shave off some more. Remember less is better or you may damage the door's structural integrity.
The size of the jamb of your door is one of the more important things you need to know. If the jamb you have is too large, it will have to be trimmed to fit the wall. If it is too small, then the framing lumber will be exposed, making a rather unattractive looking doorway.
The jambs of a window outside the frame are called “reveals.” Small shafts to doors and windows with caps and bases are known as “jamb-shafts”; when in the inside arris of the jamb of a window, they are sometimes called "scoinsons."
A door reveal refers to the space between the edge of a door and the door frame. This space is also sometimes called a door jamb or door stop. The reveal serves several important functions in the construction and operation of a door.
This will give you room to space the door frame off of the sub-floor. Now all you need to know is how to properly frame your door rough opening. So, if you have a bedroom door that is 30″ wide (which is considered a 2/6 or 2′-6″ door) just add 2″ to the width and frame it 32″ wide.
The frame should be 3/16" wider than the slab (1/16" clearance on the hinge jamb and 1/8" clearance on the strike jamb) and tall enough (usually 1/4" - 1/2" taller) to allow 1/8" clearance on the head jamb and allow the slab to operate without rubbing on any flooring. 2.
When the door jamb is wider than the wall, you could also consider adding an additional molding piece outside the frame to hide the gap. In every case, drywall should always be flush with the door jamb. You do not want gaps between the jamb and the frame or molding.
Remember, you only have about an inch and a half available to lose from the average hollow core door. If you need to take off more than that, think about replacing the door instead.
UNDERCUT: The distance between the bottom of door and the bottom of the frame. FLOOR CLEARANCE: The distance between the bottom of the door and the top of the material directly below the door. This varies with applications, such as concrete, any floor covering and/or a threshold.
Not all doors have a solid core though, some may only be so for an inch around the sides, before becoming hollow. We will go into specific materials below, but a general rule of thumb is that you don't want to be trimming more than two inches off any door or you may risk damaging it.
Foundation Issues
In many cases, an interior door frame pulling away from the wall is a sign of foundation problems. Doorways are built plumb. When a foundation settles, the door frame falls out of plumb which can cause the frame to twist and the door to stick.
NFPA 80 re- quires gaps to be measured on the pull-side of doors. Specifically, gaps are measured at the outermost leading edge of the doors and the rabbets of the door frames.
They found that a hole the size of a typical one inch door undercut will allow about 60 cubic feet per minute of air flow. In terms of air flow to size of the hole, door undercuts come out on top. They yield about 2 cfm per square inch of hole.
If you prioritize heating, put the HVAC and vents in (or below) the floor. This principle works for return vents as well. Place returns for cooling in the ceiling where the warm air congregates and heating returns in or near the floor where the cold air congregates.
The color you paint interior doors and trim does not have to be the same — but it can be. If you are looking for a subtle door paint idea, you can paint the trim to match the door. Alternatively, contrasting colors for the trim and door could make the door pop against the wall if that is the look you want.