Bucking Out a Door for Continuous Exterior Insulation

To provide nailing for flanges or door jambs, weave lumber bucks into the exterior insulation

April 25, 2023

This is a detail for integrating continuous exterior insulation with a new exterior door. When integrating continuous exterior insulation with windows, the windows can be innies or outies; it really doesn't matter. Doors, however, MUST be innies (if they are inswing doors) or else they wouldn't be able to swing in all the way.

Fortunately, many door manufacturers will make deeper jambs; if not, make an extension jamb for the outside, as is done with innie windows.

Also different than many windows is that door is screwed through the hinge into the framing because, more often than not, little kids will use it as a carnival ride. Because foam, rock wool, or fiberglass insulation boards are not structural, it is often a good idea to buck out the door opening with solid lumber.

Here's the step-by-step on bucking out a door opening for continuous exterior insulation

Before doing much to the outside of the wall, make sure to seal between the sheathing and the foundation with a high-quality sealant. Install site-bent coil stock shaped like a j-channel to receive the foam. Make sure it is installed level, all the way around the house.
Buck out the rough opening perimeter with stock that matches the thickness of the continuous exterior foam.
At the bottom, widen the stock and fasten it well because people are going to step on it pretty much every day.
Install foam on the outside of the wall.
Seal the coil stock to the foam to keep water out, and go ahead and tape all the seams in the foam to keep water out and stop airflow. That includes the gap between bucks and foam.
Cover the Styrofoam with Tyvek, cutting the classic 45-degree cuts at the top of the door, and fold that flap up for now.
Apply a sill flashing at the bottom using flexible flashing up the jambs and out of the opening.
Continue sealing all of the layers with jamb flashing. Notice that the flashing extends from the Tyvek WRB all the way back to the stud, sealing all of the layers into one bed of adhesive.
Now we can install the door, plumb, level, and square, screwing into the door bucks and the jack studs.

All that’s left to do is integrate the door frame into the Tyvek WRB, which can be done with flashing tape.

The inside perimeter will be sealed with Great Stuff, but right now, we’re going to install some DrainVent, door casing and call it a day.