Framing a door

I need to punch a door opening between my garage and my utility room, it is a 4" concrete wall with 2x4 studs on both sides and 3/8" drywall. This makes the total width of the wall almost 12 inches. Do I frame the door like a normal interior door?
In other words, do I knock out the concrete block all the way to the ceiling and then frame in the header and then put 2x12s above the header to the top plate? or do I leave a section of concrete block above? Logic tells me better to knock it out all the way so I can construct the support better?
The other question is should I do something different with a wall this thick? It has to be this thick due to the amount of rigid electrical conduits, plumbing and water supply lines that goes onto both sides of the wall.
Thanks in advance,
MC
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lay a lintel in there, if the wall is structural, and the sides need to be tied together. Usual practice for a door like this is to punch the hole a few inches wider and taller, and just frame in a conventional wall on one end or other of the 'tunnel', to hold a vanilla prehung. You have to have room for door to swing open all the way. Have you compared the floor levels in utility room and garage? Most areas require 'living space' to be at least a 4" step up, in case there are combustible fumes in garage. Also, you will probably have to use an exterior-rated (and maybe fire-rated) door for this application, both for code, and to save on fuel bills and avoid warping. Interior doors do not handle having differing temps on each side very well.
aem sends...
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The attic above it has no partition there.

I was going to do that but thought perhaps the two feet of concrete wall is not really carrying any load effectively that way and may be by building the header and using 2x12 across will be stronger to spread the load from above.
You have to have

Yes it is the same elevation because my garage is 10" lower in general, but on one side the floor raised by 10" - a step up for a width of about 48" all the way across and that's where it meets the utility room, so the elevation there is the same.
Most areas require 'living space' to be at least

Thanks aem.
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