36-Inch Prehung Interior Doors

A 36-inch interior door is the wide one: easier to get a dresser, a wheelchair or an armload of laundry through. WBC’s 36-inch interior door is the Colonist, a six-panel prehung door, in left-hand and right-hand. Get the hand right and the opening ready, and hanging it is a one-afternoon job.

The Colonist door

The Colonist is the classic six-panel door, the raised-panel look that goes with traditional and Colonial-style trim. It’s molded and comes primed, ready for paint. If your other doors are six-panel, it matches them. A 3/0 x 6/8 size means 3 feet wide by 6 feet 8 inches tall, so 36 by 80 inches.

Prehung or slab

A prehung door comes already hung in a three-sided frame, hinges mounted, so the whole unit goes into the rough opening in the wall. It’s the right buy when the old frame is coming out, or for a new opening.

A slab is the door alone, for when you’re keeping the existing frame. It usually means cutting hinge mortises to match that frame. The Colonist units here are prehung, so they’re for jobs where the frame goes too.

Left-hand or right-hand

Stand on the side where the door swings away from you, the side you push it open from. If the hinges are on your left, it’s a left-hand door; on your right, a right-hand door.

Before you pick, think about where the door ends up when it’s open. It should swing against a wall, not across a light switch, into the bed or over the path down the hall. A 36-inch door takes a lot of swing room, so sketch the room with the hinge side and the swing drawn in before you buy.

The rough opening

The rough opening is the framed hole in the wall, and it has to be bigger than the door to fit the frame and leave room to shim. For a 36 x 80-inch prehung door, the rough opening is typically about 38 inches wide by 82-1/2 inches high, though it varies a little by maker, so check the spec on the unit you’re buying.

Measure the opening’s width at the top, middle and bottom, and its height on both sides, and write them on your sketch. Use the smallest numbers. Check the wall thickness too: these units commonly come with a 4-9/16-inch jamb, made for a standard 2x4 wall with drywall on both sides. A thicker wall needs jamb extensions.

Look at the floor across the opening. If it’s out of level, the unit still goes in plumb and square; you shim it, and a jamb leg can be trimmed so the head sits level and the door clears the floor.

What’s in the box, and what isn’t

These prehung units typically come with the door hung on three 3-1/2-inch hinges in a primed jamb with the stop on. Two things usually aren’t included:

• Casing, the trim around the door, is bought separately.
• The doorknob or lever. The door is bored for standard hardware: a 2-3/8-inch backset with a 2-1/8-inch bore. Any standard interior knob or lever set fits.

Getting it in and finished

• Let it acclimate. Bring the door into the house a few days before you hang it so it adjusts to the indoor air. In a Montana winter, with the furnace running, that indoor air is dry.
• Set it square and plumb. Shim behind the hinge side and the latch side, about every two feet, and nail through the shims.
• Paint all six sides. Top and bottom edges included. A primed door painted on only the faces can take on moisture through the bare edges and warp.
• Plan on two people. A 36-inch prehung unit is awkward for one.

The Pick

For a new or replacement 36-inch doorway where the frame is coming out, the Colonist six-panel prehung door, in the hand that swings the door against a wall. Plan a rough opening around 38 by 82-1/2 inches, and add casing and a knob or lever set.

Frequently Asked Questions

How do I know if I need a left-hand or right-hand door?

Stand on the side the door swings away from you. Hinges on your left means left-hand; hinges on your right means right-hand.

What rough opening does a 36-inch prehung door need?

Typically about 38 inches wide by 82-1/2 inches high for a 36 x 80-inch unit. It varies a little by maker, so check the unit’s spec before you frame.

Does a prehung door come with a doorknob?

Usually not. The door is bored for a standard knob or lever set, with a 2-3/8-inch backset, and casing is sold separately too.

Can I use a prehung door if I’m keeping my old frame?

Not really; a prehung door brings its own frame. To keep the old frame, you want a slab door fitted to it.