Hi, I'm Dave Osborne. With over 50 years experience as a journeyman carpenter, foreman and contractor in heavy construction I enjoyed working with apprentices and sharing the tricks of the trade that others shared with me. Now I get emails from Members all over the world and we include many of my answers in our Free Monthly Newsletters. Some of my answers include drawings and instructions specific to a project, but may also answer your questions. I use correct construction terminology, so you can confidently inform your building supply dealers or contractors exactly what you need.
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Hanging a Pre-Hung Door
Hanging doors in new construction is usually an easy process when the doors are pre-hung to the jamb. A pre-hung door consists of the door choice being from stock sizes of 32, 34 and 36 inch width by 80 inch height. Custom sizes are available at an increased price.
The jamb is the frame that is separate from the door to which the hinges are already mortised and attached. It consists of two sides and a top or header for an inside door and for an outside door a threshold, weatherstrip and brickmold is included.
The jamb is designed to stop the door flush with the outside of the wall, in the closed position. The stops of the jamb are either a separate piece of wood, or more commonly, in a manufactured jamb, are rabbeted out of solid material.
The thickness of the jamb is usually 1 1/4" on the inside and 3/4" on the outside. The standard rough opening in a wall is 2" more than the nominal size of the door. This gives a total air space, of about 3/8" between the jamb and the frame of the rough opening for shimming and adjusting the jamb to be plumb and square. The other 1/8" space is for clearance between the door and the jamb itself, so it won't rub on each other, after painting, etc.
When ordering a pre-hung door unit you need to specify:
A carpenter is aware of slight inconsistencies in framing and we refer to working with them as "cheating" to make it right. If the door frame is out of plumb from one side to the other, we can adjust the jamb in or out a bit on the bottom to compensate. With the door attached to the jamb, we can see exactly the amount we need to cheat it in or out so the door will close against the jamb at the top and the bottom. With a double door set or French doors, if the sides of the frame are not in the same plane, we have a problem of getting the doors to meet at the bottom. But, with the doors pre-hung on the jamb we can cheat the adjustment of the jamb in or out. The door casing will then cover our adjusted jamb.
In areas where the door opening is built from brick, concrete block or stone, etc. a wooden frame is attached to the masonry opening. The frame should allow for a jamb, as well. We do this in wood frame construction, the rough opening allows for 2" of jamb and airspace for wooden wedges, as discussed above. If the wood frame is the jamb itself or the wood door will fit a steel jamb which is already mounted in place, we follow a different procedure to hang the door.
Hanging a Door That is NOT Pre-Hung
Measure the width and height of the opening where the door will fit into the jamb. We usually have 1" clearance under the door to enable the movement of air in our modern air tight homes. Cut the door about 1" less than the header of the jamb to the finished floor. Cut the width of the door about 3/16" (5mm) less that the width between the jamb. Check near the top, center and bottom in case there is any variation.
Stand the door into position, resting against the stops of the jamb on the sides and the header. Wedge it up on the bottom. Scribe around the door to leave a margin of about 3/32" (2.4mm) clearance from the jamb on the sides.
Lay the door on the floor lengthwise so it is resting on the lockset edge with its hinge edge up. Brace the door in this position so it doesn't fall over. From the top of the door measure 7" down to the top of where the top hinge will go and mark it. From the bottom edge of the door measure up 11" to the bottom of where the lower hinge will go and mark it. For the center hinge, measure dead center between the two marks you just made.
If you are fitting a wood door to a steel jamb, as in a masonry wall, the steel jamb will already have the insets for the hinges welded in place in the jamb. Get the correct size of hinges to fit the jamb and fit the position of the hinges on the jamb to the door. The instructions below are for fitting a wood door to a wood jamb.
For standard 3 1/2" and 4" butt hinges, I use a butt marker.
This is a handy little tool, used as a gauge and marker. Use the one that is the same size as your hinge. The butt marker has folded down stops that rest against the outside of the door and sharp edges that match up with the hinge's side, top and bottom. The top of the butt marker is placed into position at the 7" mark and while holding it in place against the outside of the door, give it 2 light hammer blows, one near the top of the butt marker and one near the bottom to mark the perimeter of the hinge.
If the hinge is not a standard butt hinge, but is an extended hinge to swing the door further away from the casing to lay against the wall, place the actual hinge in position on the door and scribe the 3 sides with a sharp pencil or the sharp edge of a chisel. Use a chisel or if you own a router and hinge router template use them to mortise out the edge of the door to fit the thickness of the hinge. The 3 1/2" butt marker is for inside doors and jambs, making a mortise of 1 1/8", which leaves about 1/4" of wood left on the edge of the hinge. The 4" butt marker marks a 1 3/8" mortise which leaves a 3/8" reveal of wood against the inside of the hinge on outside thicker doors and jambs.
Once the hinges are marked, sharpen up your chisel, a 1" one works well. Lay the chisel edge on the marked hinge perimeter and lightly tap along the 3 sides. Don't tap the chisel too hard along the inside edge or the thin wood reveal will split off. Now tap the chisel inside the area of the mortise about 3/8" apart from top to bottom. Clean the shavings out, continue this procedure until the mortise is the correct thickness for the hinge. Do this for all three hinges.
Keep the hinge pins inserted for now, so you don't make a mistake in fastening the wrong side of the hinges into the door. Just be sure to watch the location of the pin which shows the top and bottom of the hinges. Fasten them in place using the screws supplied with the hinges, orienting them with the top of the door. Pre-drill for the screws with the right size drill and screw the hinges in place.
Now place the door into position in the jamb again with the loose hinge swung out of the way. Wedge the door up again so the clearances are all good. Mark the position of the hinge on the jamb with that sharp pencil or the chisel. Remove the door and mark the hinges again on the jamb. Follow the same procedure that you used on the door mortises for the ones on the jamb. Take the hinge pins out and try the other side of the hinge in the mortise on the jamb. When happy with the fit, pre-drill for the screws and fasten the hinges in place.
Locate the door to the position and starting with the top hinge, place the pin in the barrels of the hinge. If the center hinge is out a bit, with a hammer tap the barrel of the hinge up or down until it fits. Do the same for the bottom hinge.
Check the clearances on the latch side of the door so it is even from top to bottom. Use a jack plane to even it out or a power plane or belt sander if available. Measure up from the floor to the center of the latch on the edge of the door 36" to 40". Keep the same latch height as the existing doors in the house.
Transfer the center mark on the door edge, using a tri-square (or equivalent) to each door face and measure the backset from the edge as shown in your instructions with the lockset. I use a 2 1/8" holesaw for the knob. Drill from both sides to prevent chipping. Now drill for the latch with a 1" speed bore bit through the edge of the door, through the knob hole into the door by about 1/2". Try the latch in place, if it needs to be deeper, pull it out and re-drill.
The latch can either be a drive-in without a plate or one with a plate. Mortise out for the plate similar to that done for the hinges. Screw or drive in the latch, so it is flush with the edge of the door. Place the knob into the hole, with the shaft going through the latch. Make sure the keyway is on the outside of the door. The screws should be on the inside of the door for a passage set, as well as locksets.
If the door is hung correctly, the door should stay where it is at any position of its swing. Mark the center of the latch on the jamb. Use the center of the latch itself, in the door. Swing the door into almost the closed position to mark accurately.
Depending on the size of latch (strike) plate, usually a 5/8" speed bore bit is used with a double center, one above the other. Clean the hole up with a 1/2" chisel. Follow the instructions that comes with your door lockset.
Install the door casing to cover the edge of the jamb and the edge of the finished wall. Usually, a reveal of about 3/16" is standard — never have the casing flush with the jamb. I like to put a small bead of paintable silicone/latex acrylic caulking on each side of the casing, as well as between the miter joint.
As a carpenter who does not like painting, I try to purchase the jamb and door, as well as the casing, already primed. I paint the first coat on the casing before installation and fill and sand the holes and apply the second finish coat on the wall.
I hope these instructions make the installation of your door and casing easier.