How much excess space do I leave in the frame for a pre-hung, split jam door?

Question

I'm building a frame for a pre-hung, split jam (is that the word?) door. The door is 28'' x 80''. I know it's customary to build the frame slightly larger to accomodate the door, but I have heard different suggestions: 3/16'', 1/2'', and even 2.5''!! What's the consensus?

(Any other tips would be appreciated. I've read some online articles so I have the general gist.)

Answer 1

Size the opening 2" wider than the nominal dimension of the door. For a 30" door, you will leave a rough opening of 32". This will allow for the 3/4" jambs on each side plus 1/4" on each side for shimming. Hope this helps.

Answer 2

You're actually asking 2 questions. A pre hung door is already in the frame. Your opening should be approx. 2" larger in width and 1" in height to allow for shimming. For instance a 30" door has a 3/4" jamb so the jamb is 1-1/2" wider than the door( jamb on both sides) and 3/4" taller (jamb only on the top or head). If you are hanging a door in an existing frame, clearance from the door to the frame should be 1/8" +-.

Answer 3

Door Jamb is the vertical piece of the door casing that the lock bolts extend into from the door.



The space around the casing depends on how plumb and level your carpentry is. The farther out of plumb and level, the larger the opening needs to be so the door casing can be set plumb and level.



If you haven't done this before, leave a 1/2 inch of space all the way around the door casing. Use pieces of ply wood or shingles for shims to plumb and level the door casing. Once you have it set where you want it, nail the casing and shims into place. Put plywood between the jamb and framing so the holes for the lock bolts will be in solid wood and make the jamb harder to kick open. Fill around the casing with expanding foam insulation to make a good weather tight seal,

Answer 4

Good answer above.

If you're buying the door new, you'll find recommended rough frame opening size on the packaging.

Remember to buy a bundle of shims.

Answer 5

The door frame should be the size of the door plus 1/8" each side and top. The gap at the bottom of the door should be enough to accommodate what ever your floor covering is, sheet vinyl, carpet, etc.



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