Instructions / Assembly

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Choosing the Correct Pre-hung Door Size and Handing

What Size is my Rough Opening?

Getting the rough opening size right the first time will save you a lot of frustration when

installing your doors. Framed rough opening sizes are actually simple. Just add 2” to the

width of the actual door size and 2-1/4″ to the height of the actual door size

Why Does the Rough Opening Need to be Bigger than the Door and Jamb?

Three Reasons:

1. Room to adjust the door and the frame in the opening. Not all rough openings are

completely plumb and square. Leaving this extra space allows you to perfectly plumb,

level and square your door installation.

2. Next, not all doors are the exact same size. The sizes of the door will vary by

manufacturer. Normally this isn’t much, but if your rough opening was tight, or exactly

the size of the door and the jamb, you may not get the door to function properly without

having room to adjust.

3. Finally, this leaves room for expansion and contraction of the wall. Yes, your wall gets

bigger and smaller as the seasons change. It does this by taking on moisture when it’s

humid outside and shrinks when temperature and humidity levels drop.

Again, we are talking about small amounts, sometimes less than 1/16″ of an inch, but this

can be enough to make that once perfectly fitting door start to stick, rub on the frame or

not latch properly.

Rough Opening Tips

•Verify the width and height of the door frame are each 1/2″ smaller than the rough

opening width/height.

•Verify the rough opening is square. The diagonal measurements should be the same.

Maximum allowable deviation from square is normally 1/4″.

•Verify the rough opening is level and plumb. The maximum allowable deviation is 1/8″

to 1/4″.

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Choosing the Correct Pre-hung Door Size and Handing What Size is my Rough Opening? Getting the rough opening size right the first time will save you a lot of frustration when installing your doors. Framed rough opening sizes are actually simple. Just add 2” to the width of the actual door size and 2-1/4″ to the height of the actual door size Why Does the Rough Opening Need to be Bigger than the Door and Jamb? Three Reasons: 1. Room to adjust the door and the frame in the opening.
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What is my Door Handing? The easiest way to determine your door handing: Step into the open doorway with your back to the hinges. You will be standing sideways in the opening, looking at the jamb side where the door latches. If the door and hinges are on the left side, it is a left-hand door. If the door and hinges are on the right side, it is a right-hand door. Simple. How to Measure Your Rough Opening 1. If you are measuring for a new construction, skip to Step 6. 2.