How to Measure Rough Opening Size

The rough opening is the space where the door jamb will fit
How Rough Opening Size relates to Door Size

The rough opening should be 3/4" wider and 1/2" taller than the outside dimensions of the door jamb in order to easily fit the jamb into place.

If you are replacing an existing door
It will be necessary to remove any interior trim around the door so you can see the house framing. Then you will need to find the studs that define the rough opening. Also, remove the threshold so that you can see the subfloor. If the threshold cannot be removed, you will need to establish the position of the subfloor with a probe.

Rough Opening - Width
Measure the width between the studs at three places - at the top of the opening, at the middle, and the bottom. The smallest of these measurements should be recorded as the 'rough opening' width.

Rough Opening - Height
Measure from the sub floor to the header beam above the door. For a straight topped door, measure on both sides and record the smallest measurement as the rough opening height. If you are replacing an arched door then also get the measurement in the center. In this case, the center measurement will be the rough opening height and the difference between the center and the outside corners height is the amount of "fall" on the arch. If you have any confusion or question about this please contact us.

Here is a schematic of a single door showing the relationship between Door Width, Jamb Width and Rough Opening Width:

Measuring Wrought Iron Door

For New Construction
The same rules apply for a new door as a replacement door. The rough opening must be ¾" wider and ½" taller than the outside dimensions of the door jamb. However, in many new constructions it may be possible to modify the building to fit the door unit to some extent. This will depend on other factors affecting the building design and also on how far along the building construction has proceeded. If you are in the design stage it is worth considering the whole design of your entryway and foyer in relation to the possibilities of door, sidelights and transom options. It is often noted by many real estate experts that the house entrance is one of the most important aspects that affect the appeal and the value of a home.

Threshold Height and Flooring
The Threshold is the sill at the bottom of the door that forms a barrier between the inside and outside. It also is what the dropseal on the bottom of the door seals against when the door is closed. All Donatello entry doors have an integral Threshold. If you require a door with no threshold (as with an internal door rather than an entrance door) please contact us.

The nominal distance from the bottom of the threshold to the bottom of the door is 2", however the actual threshold height is less than this to make room for the dropseal. If you are adding carpeting, tile or other flooring after your door is installed, the maximum safe depth of that flooring is 1 1/4". If your flooring will be deeper than this then you will need to raise the threshold sufficiently. The rough opening height will be effectively reduced by the amount you raise the threshold. Please see the following diagram: Wrought Iron Door Threshold