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Building an interior door jam


DrB323's Avatar
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11-08-12, 06:59 PM   #1  
Building an interior door jam

Is there a formula to follow to measure out the rough opening needed for an interior door? My situation is I need to find out the rough opening for building a door jam for a double French door. The 2 doors measure 30" wide and 80" high each. If it matters, one door would be stationary (latched) and the other would be the swing door. I have not yet determined the trim work around it yet.
Thanks!
Mike

 
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11-08-12, 08:18 PM   #2  
Rough opening is always at least 2" larger than the doors are. In your case you will want to add a little more since these are double doors with some clearance between then.... so maybe add 2 3/4, as detailed below.

If the doors are really exactly 30", and you are using a 3/4" thick jamb, you'd probably make the jambs 61 7/8 x 81 3/4" (outside dimensions) or 60 3/8 x 81 (inside dimensions) Note: (If you get jamb stock that is thinner than 3/4"... as some veneer jambs are thinner than 3/4"... make sure you go by the interior dimensions above as you cut and assemble the jamb.)

That would allow for 1/16" + 30" + 1/4" + 30" + 1/16".

So I'd make the RO 62 3/4 x 82 1/2". Having roughly 1/2" of room per side allows for shimming in the event that any framing is out of plumb.

 
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11-08-12, 09:17 PM   #3  
Perfect! Thanks for that info. I'll go with that. Should be a fun project. The doors I'm using are old, old oak doors and heavy as all-get-out! The trim I'm going to pick out will give it a nice old classic look.

 
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11-09-12, 05:12 AM   #4  
If your doors are unusually heavy, as you say, you may want to consider using 5/4" stock for your jambs and adjust your RO accordingly.

 
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11-09-12, 05:16 AM   #5  
Or use 3" screws in the hinges that extend into the framing and stick with the 3/4" if space is a premium.

 
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11-09-12, 06:01 AM   #6  
At a minimum, use 3/4" solid oak for your jambs, not the wimpy veneered jambs that are pre-mortised.

 
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11-09-12, 07:24 AM   #7  
Yes they are very heavy. I'll take your advice regarding the jamb materials and screws.

 
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