I have a garage with an odd size entry (not bay) door. The old door, which recently broke, was only 24" x 70".

Time to put in a new door. My intent is to enlarge the opening for a more standard size. I expect this will be cheaper while also improving the structure. In fact, I can see the space where there was once a wider opening... it measures at 36" rough, which would have fit a 34" door. It should be very easy to restore this old opening, and I can get a 34" x 80" prehung door at a reasonable price.

No word yet on why a previous owner put in such a weird door ¯\_(ツ)_/¯

The problem is the height. My understanding is a 34" x 80" door needs a 36" x 82" rough opening. The entire height of the garage wall from the concrete to the bottom of the beam is only 81 3/4".

Will I be able to make the standard door fit, or will I need to do something custom? If it will fit, will I need to do anything extra to make it work?


I installed the same size door in a hallway to isolate a second bedroom and bathroom. The actual frame needed 82 inches but the door is 1 inch shorter than the frame. I guess it's to allow for carpet, threshold, etc. You can easily saw off 1/4"+- from the bottom of the frame to get your 81 3/4" height. You'll still have room for a threshold. Good luck.

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  • Go to your local big-box home-improvement store.
  • Head to the tool section an pick up a nice tape measure.
  • Wander back to the doors & windows department.
  • Find a nice 34x80 door
  • Use the tape measure, still in its factory packaging, to measure the outside dimensions of the door you've picked.
  • Return the door to the rack*
  • Return the tape measure to the tool section*

Odds are it will fit just fine.

I have to admit, I've heard of 32" & 36" as standard door sizes. 34" is a bit unusual to me.

*Unless, of course, you need a tape measure and you happen to really like the door you pulled off the shelf.

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  • I live in rural Nebraska. The nearest big box is 53 miles. I like to know what I'm doing before I make the trip. – Joel Coehoorn Nov 8 '19 at 14:35
  • Fair enough @JoelCoehoorn... :) I'm a mere 20 miles from mine. If you don't have a definitive answer by then, I'll measure mine when I get home - the garage door isn't trimmed on the inside, so I can easily measure the outside jam dimensions. – FreeMan Nov 8 '19 at 14:49

Checking online there are the actual unit dimensions for these doors on the "Big Box" websites. I am finding the actual sizes are 81 5/8" in many cases. Tight for your opening but a little off the header will get it in. As a note, this is for an exterior door. Typically interior doors are perhaps a 1/2 shorter. If the header needs a 1/4" taken out of the bottom, and you have a 2x6 header for a 36" rough opening, there will be no issue. The sheathing on the wall outside aids in supporting the surrounding framing.

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