Doors openings and window framing
Often a place of question in a home theater or recording studio is the doorways and window framed areas. It proves to be simple but requires some information from the builder to do it right the first time.
This video gives a quick and easy demonstration that covers everything you need to know for cutting framing material and installation of an opening.
The video does use the words “always frame the opening 2 inches bigger”, but doe not completely explain why. That reason is the jambs of a typical door are made from 3/4 inch stock. This is equal to (2 X 3/4″) 1-1/2″. Take 2 inches and subtract the known 1 1/2 inches and you are left with 1/2 of an inch. That gives you 1/4 of an inch on either side of the door jamb to plumb the frame up. The 1/2 inch is also your wiggle room to move the jamb left or right in order to get an exact plumb on the door opening in the event of an out-of-plumb rough framing job.
If you were constructing a sound proof or well isolated wall, like for a home theater or audio recording room, you would use different jamb thickness material. It is not uncommon to see a full 2X being used as a door jamb! Reason being is that solid core doors are used for sound isolation and these are heavy, heavy doors that can put so much pressure on a framing member that it warps or pulls the door loose from the hinge side, over time.
So this would require that a different number other then 2 inches be used for your framed opening. Taking a 2X we can measure and see that it is actually 1-1/2 inches. This, plus another 1-1/2 inch board yields a 3 inch measurement. Add the 1/2 inch wiggle room and your opening is now 3-1/2 inches. So plan it out, make sure you take the measurements and write them down so you are more confident when framing this door opening.