Measurement Guide

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How to Measure for an Exterior Prehung Door

A pre-hung door is a door that is already hanging in its own frame. It's an all-in-one package that ensures

the smoothest possible installation of your door.

We recommend a prehung door if your situation is one of the following:

1. No existing door frame

2. The existing door frame is damaged

3. New construction

Note:

When installing an exterior door, unless you are a pro, it's extremely hard to tight-fit an exterior slab

door.

 Prehung doors come with weather-stripping and are tight-fitting off the shelf.

 A tight-fit door will save you on your energy bill.

What to consider when buying a pre-hung door?

 Make sure the new door frame will fit the rough opening. We recommend a rough opening that

is slightly larger than the outside unit dimension of the new prehung door. This allows for

shimming to level the unit.

 Jamb width refers to the thickness of the wall. The jamb needs to cover the stud plus any wall

application such as dry wall or sidings.

 Know your door handing (swing). Stand with your back against the hinge-side of the frame and

extend an arm in the direction you wish the door to open. If you extended the left arm, then

you need to order a LEFT-HANDED door. If you extended the right arm, then you need to order

a RIGHT-HANDED door.

 Though exterior doors typically swing inward, outswinging exterior doors are available. So be

sure to add "inswing" or "outswing" to your notes before ordering.

Door size. Measure the width and height of your old door. Round these up to full inches to find the size

of the replacement door you’ll need. If, for example, your door measures 35-3/4 in. wide and 79-1/2 in.

tall, you’ll order a 36 in. by 80 in. door. For double doors this will be the total of both doors. For

example, two 36 in. by 80 in. doors equal one 72 in. by 80 in. door size. Similarly, for a single door with

sidelite(s), the width of the sidelite(s) will need to be added to the door width.

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How to Measure for an Exterior Prehung Door A pre-hung door is a door that is already hanging in its own frame. It's an all-in-one package that ensures the smoothest possible installation of your door. We recommend a prehung door if your situation is one of the following: 1. No existing door frame 2. The existing door frame is damaged 3. New construction Note: When installing an exterior door, unless you are a pro, it's extremely hard to tight-fit an exterior slab door.
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Jamb (Frame) width. Measure from the backside of the interior trim to the backside of the exterior trim (Figure A). Specify this jamb width when you order your new prehung door. This guarantees that the interior trim will fit flush to the wall without adding “jamb extensions.” Rough opening. You’ll have to remove the interior trim to get accurate measurements of the rough opening. Measure the opening width between framing members and from the bottom of the sill to the top of the opening.
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Height: Add 1-3/4 in. to the height of the actual door *For outswing unit height, add 1 in. to the height of the actual door Rough Opening: Width: Add 2-1/2" to the width of the actual door Height: Add 2-1/4" to the height of the actual door *For outswing rough opening height, add 1-1/2 in.