Question

What is the size of concrete rough opening for a door that is 3'-6" wide x 7'-0" high with 2-1/4" Jambs.  Common sense would be to add the door dimensions to the jams so that the width of 3'-10 1/2" x 7'-2 1/4".  However, is there an adjusment that needs to be made for tolerance associated with the door jams.  The reason I ask, is that we have been specifying a width of 3'-10" which is being questioned by our customer.

Answer 1

Frank,

Thanks for your question. I copied the below from our page here http://www.commdoor.com/hmf.html.

Rough opening size, welded frame: Take the nominal door width and add 4 1/4" and the nominal door height and add 2 1/4". Keep in mind that on a 3070 door, the nominal measurements are 3'0" x 7'0" while the actual measurements are 2' 11 3/4" x 6' 11 1/8". Using a 3070 door as an example, the rough opening size for a welded frame would be 3' 4 1/4" x 7' 2 1/4". Since the standard face on a hollow metal frame is 2", the outside dimensions of a 3070 frame will be 3'4" x 7'2" so this RO dimension will give you 1/8" - 1/4" of "play".

Now, your door is 3'6" wide and you say you have 2 1/4" jambs. I am assuming you are referring to the face of the frame and not the jamb depth. In other words, where a standard frame has a 2" face (as shown below), you have a 2 1/4" face. So, the rough opening you need will be 3'10 3/4" x 7'2 1/2".

Steve Behrens

Steve@commdoor.com

Commercial hollow metal doors, frames, and hardware.

http://www.commdoor.com