Removing The Old Door And Preparing The Opening

  Removing the old door is fairly easy. Drive the pins out of the hinges, using your fingers if they are loose or a hammer and screwdriver if they are tight. Slide the door off the hinges and discard - unless you can use it at the cabin.
    Next, pull off the interior casing and exterior brickmold or other trim. Most people probably won’t reuse any of this stuff, so use the claw hammer to pry it loose, being careful not to dent either exterior siding or interior walls.
   Once the trim is off, the nails that fasten the old frame in the opening should be visible. There usually are two or three on each side, and none on the top or bottom. Either drive the nails all the way through the frame with a nail set, or cut them off behind the frame with a sawzall or hacksaw. Remove the frame and set aside. That’s pretty much it, if your new door takes the same rough opening.
   When looking at putting in a wider door unit, the next step is to open up the wall on one or both sides of the existing opening. First, shut off electrical power to the area for safety’s sake. Then, remove the drywall from an area on the inside about a foot wider and higher than the new opening. Remove the plastic vapor barrier and the insulation. If there is plumbing or electric wiring, have these removed. Don’t worry about the exterior siding just yet.
    If the ceiling joists run perpendicular to the wall in which the door is, be concerned with the structural header over the new opening. Erect a temporary support wall of 2-by-4s about 3 feet into the room from and parallel to the door wall. Start widening the opening by removing the support studs and the old header and installing a king stud (full height) at the end of the new header and a trimmer stud inside each king stud to support the new header. Cut the trimmer stud to the length between the bottom of the header and the bottom plate of the wall. The width between the trimmer studs should be the rough opening of the new door, making the length of the header 3 inches wider.
    The size of the header required depends on the width of the new opening and the load bearing on it from above. Don’t guess at this size; ask a structural engineer to calculate it for you. A few dollars spend on this can save many more in the long fun.
    To locate the opening to be cut in the exterior siding, drill a hole from the inside through the sheathing in the upper right corner and upper left corner of the new rough opening. Locate these holes from the outside and snap a horizontal line between them and a vertical line down from each one. Cut along this line with a circular saw to trim the siding and sheathing back to the rough opening size. We’ll trim it back later to accommodate the exterior door trim, so this cut needs to be straight but not necessarily perfect.
    You are now ready to test fit the new door. First, make sure the subfloor is level. If not, use shims, either plywood or hardwood, to level the door. Check too that the subfloor level will allow the bottom of the new door to swing about 1/2 inch above the floor covering nearby. It may be necessary to build up the subfloor here with a plywood strip.  

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Installing the New Door and Trimming it Out

    When these conditions are met, stand the new door in the opening and trace the outline of the exterior door trim (attached to the new door unit) onto the siding. Then remove the door from the opening. Using a circular saw with a sharp blade, set the blade depth to just cut through the siding, but not the exterior wall sheathing. Since this cut must be clean and accurate to fit snugly up to the door trim, you may want to tack a 2-by-4 onto the siding to act as a saw guide. I know my free-hand cuts with a heavy circular saw can tend to wander a bit.
    Now we’re ready to fix the new door in place permanently.
    Run a bead of good caulk down the back side of the exterior door trim and under the sill. This will seal the points where the new door contacts the house and prevent air and water from leaking in. Slip the frame into the opening, using your level to make sure the side jambs are perfectly plumb and the head and sill are level. Tack the door in place with 16-penny galvanized casing nails. Don’t set them all the way until you are sure the door closes perfectly. Insert shims between the jambs and wall framing from the inside to make adjustments to the frame as needed.
    When you’re satisfied, drive 16-penny casing nails through each set of shims to hold in place. Then nail through the exterior trim into the wall studs, using one nail every 16 to 20 inches.
    Insulate around the door frame from the inside, partially filling the gap between the stud and door frame with a bead of expanding spray foam. Lightly pack the rest of the gap with strips of fiberglass insulation. I don’t recommend filling the entire gap with expanding foam, since this much foam can actually bow the frame inward, causing the door to stick.
    Run another bead of caulk around the exterior door trim to fill any gaps between the siding and door trim and the outside is done. In some installations, though a galvanized sill flashing and drip cap at the top of the door outside are advisable, especially if the door is on a side of the house where it is exposed to wind-driven rain or water running down the siding.
    On the interior, finish any wiring and plumbing that had to be altered. Replace the wall insulation and vapor barrier, being careful to use vapor barrier tape to seal the overlap between old and new vapor barrier. Finish out with new drywall, paint it and install wood casing around the new door frame and the installation of a new entry or patio door is complete.