How To Install A Split Jamb Pre-Hung Door

By Todd Fratzel on Doors, Finish Carpentry

Split Jamb Pre-Hung Doors

split jamb pre-hung doorHanging a split jamb pre-hung door is a very easy home improvement project. We ordered all the doors for our new house at the same time, including the basement ones. The basement doors have been sitting in the basement in the original packaging for over a year now. So I decided it’s time to get the basement organized, so today I hung a couple of the doors in the basement.

As you can see the doors in our new home are all six panel colonialist textured hollow core doors. We ordered them all with 2 1/2″ primed colonial casing. When you buy a split jamb pre-hung door you need to know what type of casing you’ll be using. As you can see in the second photo the front and back casings are attached to the two halfs of the jamb (hence the split portion of the jamb).

Installing Split Jamb Doors

split jamb frameThe first step is to take apart the frame. This is done by simply pulling the front molding and jamb away from the back molding and jamb. As you can see in the photo there is a slot in the main jamb that accepts the back jamb. The door is already attached to the main jamb with hinges.

Once you remove the jambs you’re ready to hang the main jamb with the door. Place the jamb and door in the rough opening (I’m assuming you already have built the rough opening, this example is a 2-6 door (30″) so the rough opening is 2′-8 1/2″ wide, typically you add 2 1/2″ to the opening width).

You’ll want to position the door in the opening and try to square it as best you can. Place a level on the top and sides to make sure the door is level and plumb. In this example I’m installing a door in a storage room, so there is only drywall on the hall side. leveling split jamb frameI’ve installed some 1/2″ shims between the door casing and the wall framing to make up for the lack of drywall. Once the door is level and plumb then you can attach it using some 10d finish nails. You nail directly through the casing into the wall framing.

The next step is to work from the other side of the door. Now all you have to do is install the remaining split jamb. In the photo below you can see the door from the hall side with the slot that accepts the remaining jamb. split jamb frame outsideAll you do is simply slide the other jamb into the slot and slowly work it together until it is tight up to the finished wall. Again nail the casing with 10d finish nails and you’re finished.

The only thing left to do is install the door knob set and strike plate. If your rough opening is the correct size and you have all the tools you’ll need this project will take approximately 10 minutes from start to finish. So next time you’re buying a pre-hung door and you know what the casing will be I suggest you look into a split jamb pre-hung door. The time savings is great and it really saves on trimming out the door.
finished door

About the author

Todd Fratzel

I'm full time builder for a large construction company in New Hampshire. I run their design-build division that specializes in custom homes, commercial design-build projects and sub-divisions. I'm also a licensed civil and structural engineer with extensive experience in civil and structural design and home construction. My hope is that I can share my experience in the home construction, home improvement and home renovation profession with other builders and home owners. I'm also the Editor-in-Chief and Founder of Tool Box Buzz. Please feel free to contact me if you have any questions, suggestions or you'd like to inquire about advertising on this site.

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  1. Jennifer says:

    What an interesting concept… I didn’t even know those existed! SUre is tempting right now as we struggle and fail to install our non-prehung door. SIgh!

  2. Joe Staniford says:

    What brand were your split-jamb doors? I have been having trouble finding a source for this type of door. I would appriciate your help.



    • Todd says:

      @ Joe – I actually buy my doors from a local lumber yard that has a complete door shop. However, they buy quite a bit of there materials from Brosco supply I believe. Your best bet if finding a local lumber yard that builds doors and services them. What part of the Country are you in?

  3. Joyce says:

    We just bought one today from HOME DEPOT!

  4. rob casstevens says:

    i have a 36″ interior luan door and would like to add a window of some sort to it. is there a retailer out there that sells these items?

  5. Jeffrey says:

    I am trying to install a split jamb pre-hung door and having some issues with shimming and squaring the door. First off, the rough opening is perfectly level and square and the right size for my door. Being such, I figured this would be a breeze. However, even though my level shows dead center in the bubble on each side and top of jamb, I have a large gap on the knob side and tight fit on the hinge side and binding and flexing of the lower hinge as I attempt to close the door. The door swings out fine, and doesn’t drift either way, but just as it’s about 2 inches from latching, it has sort of a “bounce” to it and the lower hinge flexes. I’ve tried shimming until I’m blue in the face…any ideas what I’m doing wrong or overlooking? Thanks.

    • Todd Fratzel says:

      Jeffrey – Split jambs can be tricky. The problem is the jamb itself is rather flexible so while the rough opening is square and plumb, the jamb can move easily. Does the split jamb having casing on it already? if so, you need to set the door in the opening….close the door…move the jamb as necessary while you tack the casing…once it’s good then you can nail the jamb, be careful not to nail too hard as you may move the jamb out of plumb. if all else fails, remove the casing from one side so you can shim behind the jamb. Good luck.

  6. Lois Fletcher says:

    I am trying to repair existing split jamb doors in our house that we recently purchased. The frames are over 20 yrs old and are coming apart at the casings and top split joint. The casings have cracked and pulled away from the wall at the top joints. I removed the casings on main side and am going to shim between the jamb and 2×4 wall framing. My questing is, would you use a nail gun to attach the jamb to the shim/2×4 or countersunk wood screws? And where would be the best place to start? Top, middle or bottom? If you could provide a quick tutorial of how you would proceed, that would be great! I have three doors to fix :( .

    • Todd Fratzel says:

      In my opinion….either a long screw (you’ll need to countersink so you can fill the holes) or a hand driven larger finish nail. Nail guns won’t have the holding power you really need.

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