Double Doors Are Twice As Tricky

Synopsis: Installing prehung double doors can be a pain, but Rhode Island builder John Spier has come up with a methodical system for getting them in place with as little trouble as possible. By using galvanized nails, shims, a level, a keen eye, and a minimal amount of movement, Spier is able to get doors in place and working smoothly in almost no time.

Prehung double doors are a pain. These doors come from the manufacturer bristling with temporary bracing and nails to hold them together, but once this bracing is removed, moving the doors without damaging them is difficult. I don’t think anybody should specify prehung double doors wider than 4 ft., but nobody listens to me. i’m often faced with 5-ft. or even 6-ft. doubles, so I’ve learned some tricks for getting them hung and adjusted without wasting too much time.

Galvanized nails allow for adjustments

Although most doors are set plumb in their rough openings with cedar shims and are fastened securely with a 15-ga. air nailer, I change things up a little bit when it comes to prehung double doors. Because these doors usually require a lot more adjustment to get the right fit, I use 10d or 12d galvanized finish nails to tack the jamb legs in place, relying on their friction against the wood to provide an adjustable fit.

One of the most-frustrating things about double doors is that after the gaps are all perfect, the bottoms of the doors usually are still misaligned, one in front of the other. Galvanized finish nails bend just enough to allow me to move all four corners of the jamb in or out slightly until the doors are in plane. In extreme cases, i might need to pull one and renail it, but it’s still more convenient than digging out a flush-driven pneumatic nail.

Shim placement matters

When it comes time to back up the galvanized nails with additional permanent shims, I start by snugging up the loose shims behind the upper hinges, then adding a pair of shims just below the bottom hinges. Finally, I add a set just above each middle hinge.

I never put shims directly behind the hinges because they’re a lot harder to cut off there, especially if the door opening is close to an adjacent wall. Also, the hinge screws often come through the back side of the jambs just enough to interfere with the shims. I never shim the head jamb because all buildings move, all headers settle, and an unnecessary top shim just invites a jammed door later. The casings hold the head jamb straight.

Double Doors Are Twice As Tricky

Level, But Don’t Plumb

Before I start, I lay down a few pieces of cardboard in front of the opening to protect the door and the floor. Then I lay the door on the floor, hinge side down, and remove all the temporary bracing.

1. With the door in position on the floor, I check the floor across the opening for level, figuring out how much longer one jamb needs to be than the other for the door to stand plumb.
2. After taking a measurement from the top edge of the door jamb down the jamb leg, I prop up each side of the frame and use a Speed Square to mark a cutline, making sure to leave a roughly 1⁄4-in. gap between the bottom of the door and the finished floor.
3. A small cordless circular saw is a great tool for cutting jamb legs to length without moving the frame around too much.
4. Once the legs are cut to length, I stand up the door.
5. Put the level on the top jamb to check my work. If need be, I can easily lower the doors and fine-tune the bottom of one jamb leg or the other until the top is dead level.

Nail Guns Aren’t Always The Best Option

I use five strategically located 10d or 12d finish nails to tack the jambs in place; galvanized nails work best because their coarse shanks provide more friction against the wood. This allows me to adjust the door jambs with a flat bar.

	6. The first two nails go through the side jambs just above the upper hinges, which are loosely shimmed.
	7. The second two nails go in the bottom of the side jambs, a couple of inches above the floor, with no shims. The fifth nail goes into the center of the head jamb and is the only one I set flush at this point. I sink the head into the jamb, then use a flat bar to pull the jamb down until it is straight.

Lose The Level; It’s All Visual From Here

Again using a flat bar, I can pull the bottoms of the side jambs away from the jack studs until the doors fit. I do one side first, using the space between the door and the top jamb as a guide.

8. Then I do the other side, aligning the top corners of the doors and keeping an even center space between the two doors. With the doors swinging the way I want them,
9. I can shim the jambs and fasten them securely, this time with a 15-ga. nail gun.

To see step by step photos of Spier put in prehung double doors, click the View PDF button below.