Rough opening for door?

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Old 03-27-09, 01:57 PM
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Rough opening for door?

If I am installing a 30" x 78" exterior door (that's the measurement of the actual door), what would the rough opening need to be? I was told by a door mfr it would be 32"x80", but 2" additional on the height doesnt seem like enough to me including the top part of the jamb and the sill on the bottom.
is that standard to just add 2" all the way around?
is the rough opening measured before or after installation of the sill?

thx
 
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Old 03-27-09, 02:49 PM
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Is this a slab door or a prehung? Remember RO is from bottom of header to top of any framing/sill plate. If you're making your own frame it will depend on what material you use.
 
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Old 03-27-09, 03:13 PM
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A standard exterior door is 80", plus the threshold and top jamb is about 82. Unless you ordered the door special, it is probably 80". But 30" is small for an exterior door. The usual is to add 2-2 1/2" to the door dimensions, for the rough opening.
 
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Old 03-27-09, 06:42 PM
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You don't need my opinion, but it's free. I usually go 82 1/2" high and 2" wider than the door itself. I don't like alot of shims on the sides, so sometimes I cheat, but I do it all the time, so I feel confident.
 
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Old 03-31-09, 10:36 AM
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Actual sizes

A door measured at 80" is slightly less for clearances. The framing (sill and jamb) are normally 3/4" , giving you 81-1/2" leaving you with 1/2" clearrance for shims. SO, adding 2" to the overall dimension for the door is good. If your studs are absolutely vertical, you can secure the part with the hinges directly to these studs with long screws. This would give a full 1/2" clearance for shims on the other side. If you want, make your opening to 81-34"...this will give you only 1/4" for shiming...it is up to you....

This being said, you may want to add an additional 1/2" to the overall dimension, so you can install insulation, whether it be pink fiberglass or liquid styrofoam....
 
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Old 03-31-09, 11:58 AM
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Tyler, you lost me on this one: "The framing (sill and jamb) are normally 3/4" , giving you 81-1/2".


It's my understanding that when purchasing a slab door (not prehung) it measures true to size and not slightly under. lets assume that is true for this discussion.
so my door is true 78" tall. I would need to add 3/4 inch for the jamb on the top of the door, plus a little room for clearance between the top of the door and the jamb. (1/8 inch?) Then I need to allow room to shim between the top of the jamb and the header (1/4 inch?) So total additional space required above the true top of the door is: 1/8 + 3/4 + 1/4 = 1-1/8" at a minimum. if the R/O is supposed to be 2" larger than the door then that only leaves 7/8" on the bottom for the sill and a space between the bottom of the door and the sill.

Where am I going wrong here?
How tall is a normal sill for an exterior door?
 
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Old 04-01-09, 06:26 AM
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The formula you show is correct. But since this is an exterior door, I would change the 1/4" clearance to 1/2" for insulation. Use this same formula for the sides.
 
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Old 04-01-09, 06:35 AM
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Sill height?

So is 7/8 enough room for the sill + clearance at the bottom? how tall is a normal door sill? I would have thought more than 3/4.
 
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Old 04-01-09, 07:13 AM
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For your type of installation, I would have selected pressure treated wood, 2 x 6 and then add some flashing to protect the surface...don't forget to add a slope, away from the door for your sill....
 
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Old 04-01-09, 12:01 PM
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I would frame as per manufacturer. Most exterior door rough openings, since '73, are 2-1/2" wider and 2-1/2" taller (including the threshold), than the door size. I've found that wooden doors, installed have a lot of slop------ and steel doors, have only 1/4". Some wood are under net, others are at net. Steel are plus net, so the actual door+jamb is 2-1/4". Some use 1" jambs. French door measurments are different than sliders, and they even vary by maker. It all depends on maker, use their measurments. Scroll H.D. or Lowes measurments for doors and rough openings, wood v.s. steel, etc. Be safe, GBR
 
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Old 04-01-09, 12:40 PM
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Thanks GBR. this is very helpful! I'm buying a door slab and making my own jamb for it. I need to tell the builder what size the R/O needs to be. it is a solid wood door, so it won't be too much of a problem if I need to shave a little off the bottom to make it fit, but if I can plan it out so that I don't have to...why not? I'm going to tell them +2-1/2" from the net.
Thanks!

on to the next thing on my list...
 
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