Pre-hung doors may seem easier to install than slab ones, but installing it correctly takes precise work. A pre-hung door won’t fit correctly into a wall that’s out of plumb despite your best efforts!
Verify the wall and trimmer studs are level, plumb, and square by using a hand level and plumb bob to check. Shim your door unit using wood shims every 6 inches spaced apart until securing with window and door sealant.
Measure the Opening
Before buying a prehung door, take measurements of its intended installation site – this measurement is known as a rough opening and should typically be 2 inches wider and 2 inches higher than its door size and height respectively. This extra space enables both door and frame to fit properly within their respective walls while providing room for expansion/contraction due to temperature fluctuations.
WCMA NET Window & Door suggests taking accurate measurements by first removing molding (sometimes known as trim ) from a doorway’s frame to obtain an accurate reading, then using a level to make sure all studs in it are level and square.
Next, determine whether the door should swing left or right by extending your arm towards the hinge side of the frame and pulling your finger back outward.
Measure the Jambs
Use a level to ensure that your head jamb is aligned with both the floor and trimmer studs, and adjust as necessary with shims if it’s too high or low. Once reveal is even across top, close door and check that it closes securely.
Obtain measurements from stud to stud of your frame using a screwdriver and hammer for height and width measurements, respectively. If there’s already an existing door installed in its frame, remove it by using a screwdriver and hammer and prying away its trim (also called casing). Measure all dimensions from top to bottom using your putty knife or painter’s tool before taking measurements from corner to corner for height and width measurements.
Establish the swing of a door by pressing your nose against its hinge pins and seeing which hand can reach the latch handle; typically this means right-handed inswing or left-handed outswing doors are best. Next, shim and level the jamb on that side.
Measure the Frame
Once you have your rough opening measurements in hand, take measurements for the frame of a door. A door’s frame serves to support its hinges and latches on both sides; to ensure proper function it should have an equal thickness as its door.
Beginning by disassembling the existing frame using a utility knife and pry bar. You should be able to identify door studs behind molding that may affect how the door swings open or shut. Make sure these are level – otherwise they could affect its operation.
Record the height, from floor surface to top of frame; width (measured from one door stud to another); depth; and width of frame.
Measure the Hinges
Once the hinge locations have been marked, use a level to ensure both trimmer studs are level with one another and that the jamb on the door hinge side of your hinge is square to the wall. Shim as necessary in order to close any gaps between trimmer studs and door frame.
To take measurements for door swing, hold up a door handle between its hinge pins and examine which hand can grab onto it most easily – this will indicate which direction the door opens; this is known as its “swing.” An inswing or outswing opening away from you are two possibilities available as prehung doors; bring these measurements with you when visiting a hardware store so they can assist in helping find appropriate hinges for your new door.
Measure the Door
Installing a door is one of the more challenging DIY carpentry tasks for novice homeowners, as improper hanging may leave uneven gaps along its jambs or cause it to be jammed shut when opening or closing it.
To ensure that the door you buy fits into its frame properly, begin by measuring the trim height. Take three measurements from top, middle and bottom of trim before using the lowest figure as your measurement for door height.
Measure the width of trim on the left, center, and right sides of the frame and use the narrowest figure as your measurement; if any are different use the widest measurement as your door width measurement. By following these steps you will be able to purchase and install a pre-hung door that swings freely and operates smoothly.