Replacing an Interior Door

When you do handyman work for property managers, there are some jobs that seem to come up again and again.  The toilet fill valve that we replaced last week is one of them.  Replacing an interior door is another.  Some time soon I will show you how to snake drains and patch fist-shaped holes in drywall, and you will just about be ready to set up practice as a handyman.

Hanging a door slab is super easy but, as I go into apartment units and "flipped" houses, I usually see a lot of examples of people who got it wrong:  the bevel points the wrong way (or isn't there at all), the door sticks, or there isn't enough air gap at the bottom.  Watch my video, and you won't have to worry about any of this.

Tools Needed

• Circular Saw.  I suppose you could cut the slab with a hand saw.  I've done it, but it takes a miserably long time.  Use a circular saw with a fine-tooth plywood blade if you have one.
• Router with a 1/2" straight bit or a butt chisel.  The router is faster, especially if you have a hinge jig, but a chisel will do perfectly well. 
• Portable power plane or bench plane.  Use the powered version if you have it, but a regular #4 or #5 hand plane will work fine. 
• Tape Measure
• Screw Driver
• Hammer
• Electric Drill w/ door knob drilling kit.  There are various kits out there and which one you use is largely personal preference. 
  
• Super Wonder Bar or panel jack.  This is optional for lightweight doors, but almost essential for heavy solid doors. 

Tools for Hanging Doors (Not Shown: Super Wonder Bar)

Step By Step

1. Measure the door opening.  Buy a door slab that is at least as big as your opening.  Standard door slabs are usually 80 inches high and come in width increments of 2".  If you are working in a rental you should buy the cheapest one you can find since the tenants will just destroy it again.
2. Determine which end is "up" on your door slab.  The bottom usually has thicker wood inside it than the top (knock on it to find out).  Draw an arrow or other mark in pencil so you don't flip the slab by mistake.  
3.  Cut the bottom to adjust the door slab height.  The height of the slab should be the same as the height of the door opening, minus enough space to easily clear any carpet, minus another inch if the unit has central heat or AC.  
4. Cut the door to the correct width by cutting a 1/2 degree bevel (approximately).  The width of the long side of the bevel should be about 1/6" narrower than the door opening. 
   
   
   

   

   Bevel on Edge of Door (Not to Scale)

   
   
5. Clean up the beveled edge with your plane.  The edge should be nice and straight with no visible saw marks.  At this point the maximum width of the door slab will be about 1/8" less than the width of the door opening.
6. Mark the tops of the hinge gains on the door by measuring the location of the hinges in the door frame from the top of the door opening.
7. Measure the distance between the edge of the hinges and the door stop.  Mark this distance plus a smidge on the door slab. 
   
   

   

   Transfer These Measurements to the Door

   
   
8. Hold your hinges against the edge of the door, lining them up with the marks you made, and trace around them in pencil.
9. Use either a router or chisel to cut the gains, making sure that the depth of the gains is the same as the thickness of your hinges.  
10. Screw the hinges to the door.  Use an awl or a fine drill bit to create a pilot hole so the door won't split.  If you don't have a fine drill bit you can chuck a finish nail in your drill and it will work just as well. 
11. Optional: Prime and paint the door.
12. Hang the door in the opening, using your Super Wonder Bar or panel jack to support it while you slip in the hinge pins.  Make sure the door closes without binding, knocking off any high points with your plane as necessary. 
13. Follow the instructions that came with your door-knob drilling jig to drill the large hole for the doorknob and the smaller hole for the latch barrel.  Keep in mind that latch sets can have either a 2 3/8" or 2 3/4" backset (the distance between the edge of the door and the center line of the knob) and you need to adjust the jig accordingly.
14. Shove the latch barrel into the hole as far as it will go and mark around the latch plate in pencil.
15. Use either a chisel or router to excavate the gain for the latch plate.  
16. Install the door latch and knob assembly.  
17. Test the door and make any final adjustments to the hinges or latch hardware.

Installing Trim on a Door Opening

In ordinary maintenance work, you will rarely find yourself re-trimming a door.  It is a fairly common finish carpentry task in general remodeling work, however.   I plan to do some videos in the future about trim carpentry because it is a subject with many tricks and subtleties.  For now, however, I will give you a quick sketch of the process.

Interior trim is made up of three different components:  jambs, casing, and stops.  The jambs are usually 1x boards which have been ripped to a width equal to the thickness of the walls (studs plus drywall).  They form the finish opening of the door.  Casing is the molding frame that goes around each side of the door like a three-sided picture frame. Stops are the moldings which go around the inside of the jambs, which the door closes against.

Cross Section of Interior Door Trim

Every time you trim a door you have two options.  1) Buy a pre-hung door  2) Trim out and hang the door yourself.  If you have a shop, of course, you can make your own pre-hung door units and bring them to the job site.  I have done it both ways, and I think it basically comes down to personal preference.

Installing a Pre-Hung Door

The jambs come preassembled with the stops installed and the door already hung.  All you need to do is put the unit in the rough opening, shim the sides and top until everything is plumb and level, then drive enough 9d finish nails to make sure it stays in place.  You still need to install casing, though, as described below.

Trimming Out a Door Opening from Scratch

1. Cut one piece of jamb which is 1/2" shorter than the rough opening is wide.  Cut two pieces of jamb which are 1" shorter than the rough opening is tall.  
2. Cut hinge gains in one of the long pieces of jamb.  The proper locations aren't really standardized, but these measurements should work for most interior doors:
   
   

   

   Placement of Hinge Gains on a Door Jamb

   
   
3. On the floor, assemble these three pieces into a three sided rectangle using 9d finish nails.  Square up the top corners and tack scraps of wood on to hold everything in place.
   
    

   

   Preassemble Door Jambs on the Floor

   
   
4. Place your assembled jambs in the rough opening.  Put wooden shims between the jambs and the rough opening to hold the jambs plumb and level.  
   
   
   
   
   
5. Once the jambs are in place, drive 9d finish nails though to shims to hold them in place.
6. Saw off the pieces of shim which are sticking out.  You can also just snap them off, but they don't always break cleanly.  
7. Measure the width at the top of the finish opening.  Cut a piece of stop that is just a hair longer than this measurement.  Bend this piece slightly to spring it into the top of the opening.  The flat edge of the stopshould be the same distance from the edge of the jamb as the thickness of your door.  When you have this piece positioned correctly, nail it in with finish nails.  
8. Measure from the face of this top piece of casing to the floor.  If there is not final flooring in place then subtract 1" from this measurement to leave room for the flooring guy to do his thing.  Cut the two side pieces of stop to length and nail them in.  Be extra sure that they are a uniform distance from the edge of the jambs (it helps to use a combo square set to the right distance to position them).   Nail them off.  
9. For generic "picture frame" style casing, start by cutting the top piece.  Cut one end at 45 degrees (preferably using an electric miter saw) then mark and cut the other end.  You want the bottom edge of the casing to be 1/4" from the edge of the jamb and 1/2" longer then the width of the finish opening, so as to leave a 1/4" reveal after the molding is installed.  
10. Nail up the top piece of casing, being sure that the reveal (the gap between the opening an the edge of the molding) is a constant 1/4" all the way around.  Again, a combo square is very helpful.  
11. Make the 45 degree cuts on the ends of the vertical pieces of casing.  Then return your saw to 90 degrees.  Measure the distance from the top of the top casing to the floor.  Subtract 1/2" if the finish floor is not in place yet.  Cut the pieces to this length.  
12. Nail up the vertical casings.  Always start nailing up near the miter so it holds together and does not gap.  Then four or five more finish nails at regular intervals, making sure your reveal stays constant.  
13. Repeat steps 9-12 to case the other side of the door.
14. Hang your door as described at the start of this article.

Cutting in a New Door

Don't do this at all unless you either:  1) Are absolutely sure that this is not a bearing wall.  2)  Are comfortable enough with remodeling carpentry that you know how to build a false wall and properly size load bearing lintels. 

This is actually a fairly common task that people ask handymen to do, and I promise I will do a video on it in the future (as soon as I find someone who needs to add a door and doesn't mind me filming myself do it).  In the mean time, this Fawlty Towers Episode will give you an idea of how these things sometimes play out.

-HK