Learn How to Build a Door Jamb & Complete the Assembly

guide-to-build-a-door-jamb-from-scratchThere’s this parting door frame that basically is in charge of keeping the mounting hinges on one side. While the other side works for holding strike plate. And it’s called door jamb. Some people refer to it as the legs of a door. You see these on the inner side of a door frame.

Now if you hardly know anything about many parts of door construction, then getting it confused with the frame is a very usual case. So, I’ll be covering the difference in a segment coming up next.

Also, if you are someone who wishes to have a jamb made of wood that’s similar to one your house trim has, then DIYing the jamb yourself can be a fabulous idea. I’ll help you learn how to build a door jamb all by yourself. Based on what choice of wood you are going for, there’s a very good chance that you’ll save a fantastic amount of money.

So, let’s get started with it already…

Difference Between Door Frame and Door Jamb

Before learning how to build a door jamb, you should have a clear concept of the frame and jamb. When you don’t really can see the difference between these two different door parts, it gets hard to follow up with the process of DIYing.

The most obvious difference between the door jamb vs door frame, is the fact that jamb is actually a part of the frame. You will notice a vertically going upwards flat surface on one or other side of the door frame, that’s jamb basically.

If you are targeting to build an exterior door jamb, then knowing about the other parts of frame is also important. There’s the head, sill, weatherstripping, jamb casing, and door stop apart from jamb that combinedly makes a door frame.

Even when you want to simply replace the jamb, a better option is purchasing a whole frameset. Because the other parts also play a very serious role in helping the jamb work.

The head is in charge of holding the jamb in place with its two grooves. To stop the door when the jambs are rebated, doorstop part does the main job.

Weatherstripping is another part of the frame that basically sits against doorstop as well as jamb so that a seal is there on an exterior door. This seal works for preventing the air to seep between the sill and door. The jamb casing is trims mounted for decoration purposes and usually sits on the wall around the frame. 

How to Build a Door Jamb from Scratch

Now that you know about the dissimilarities between frame and jamb, let’s get into the actual tutorial. You’ll find out about building a door jamb from scratch, so if you’re new to such home improvement projects, there won’t be much problem.

Tools You’ll Need:

  • Table saw.
  • Clear or grade 1-by-6 lumber (Wide stock if necessary.)
  • Router
  • ¾ inch straight bit.
  • Measuring Tape

Choose The Wood Material Wisely

The stock you will use should not be twisted or bent. Also, avoid any warped option. And those who are doing this for the first time, go for a cheap material choice. The less pricey clear pine can be a great choice. So that you can catch the idea of this whole process without wasting anything very experience. Once you get a hang of it, moving to the costly wood species will be a smart move.

However, if using the DIY door jamb on your door on the first try is a priority, then maybe pay more attention towards investing in some good quality material. Because otherwise your door won’t hang properly and invite further troubles.

Take Measurements

Considering the door, you need to take some precise measurements. Note down the door’s thickness, width as well as height. The accuracy should be within 1/64 of an inch.

The wall that would hold the door jamb is also something you need to measure for thickness. Go ahead and take more measurements around the door opening. This really helps to get a fine idea of the thickness measurement. Commonly, walls are 4.5 inches in thickness. But there are variations too.

Focus on these two equations,

2 Side jamb length = door height + jamb stock thickness + ¾ inches + ½ inches + 3/32 inches.

Top Jamb length = door width + 3/16 inch + ½ inch + 11/16 inch.


  1. The gap between the top jamb and door is 3/32 inches.
  2. The gap between the side jamb and door is 3/32 inches.
  3. Gap between the floor & door is ½ inch.
  4. The measurement of the side jab extending on top of the above jamb is ¾ inch.
  5. 2 Dados or deep grooves are of ¼ inches. (Basically, for the top jamb to fit and cut into side jambs.)

Use The Measurements to Make Precise Cuts

Making a door jamb definitely involves precise cuts that are based on the measurements you have taken with caution as well.

The Table saw fence needs to be set similar to the thickness of your wall and 1/16 inch more. So that there’s some extra room for out of plumb walls. Even in the case of a leaning wall, you must carry on with a jamb plumb.

Use your saw to cut a scrap piece and test the set width.  If not correct yet, make necessary adjustments before cutting the stock. Then you can rip cut the stock in the right width. Do this for three pieces and use your previously decided lengths here. The edge along with rip cuts would need slight rounding. Use sandpaper to do that.

Next, you want to place both pieces of side jamb aside each other. In a way that the inside is facing upward while ends are flushing. Get a scarp piece and clamp it on either side. while doing the groover cuts using a router, these scrap pieces will help in chip and tear prevention.

Use a straight bit of 3.4-inch diameter and set the router. The depth should be a quarter inch. Across both side jambs, you want to clamp a straight edge. This will help to cut the groove exactly into ¾ inches from the boards’ end.

Your router’s manual will have better information in case it seems difficult to use it. Basically, you need to hold the thing with firm hands and turn it on. Then let it reach the speed you need and finally, work on the wood by feeding the router bit. Make sure the base of router stays right against the straightedge. Keep on guiding the router and at one point it will cut through the scrap to exist on another side. Next, use a template to create the mortise that you’ll need for hinge installation.

Next Read: How to Cut Door Hinges with a Router & Jig


Finally, The Assembly

For the door jamb construction, you definitely need to do some assembly. Let both side pieces face each other and stand on their edges. Fix the top jamb inside grooves. Take measurements here for the distance between both side pieces. It should be around 3/16 inches plus the door width.

Take diagonal measurements from the first side jamb’s top to the other side jamb’s bottom. Now similarly take another diagonal measurement but this time with the first side jamb’s bottom to the other side jamb’s top.

If both of them are equal, then the frame is perfectly square. Both side pieces’ bottoms must be at the same distance. Just how they are at the top jamb part. You can temporarily screw wood pieces to maintain the correct parting distance between both side jambs’ bottoms.

Apply some yellow glue on the top jamb as well as inside the grooves. Remove the top jamb for better application here. Make sure you get scrap lumbers out from the bottom prior to your DIYed Jamb installation. After the jamb installation, attach hinges. You also want to add door stop molding as well as the doorstop.

Wrap Up

And that’s how to build a door jamb all by yourself as well as the process of completing rest of its assembly for a proper door installation. Such projects do need some time and patience. So even if it seems a bit confusing now, hang on there.

Also, you must maintain the necessary safety steps, wear proper gloves when dealing with power tools. Having a friend who can help you hold things would be really helpful as well. See you in some other fun project talk soon!

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