Before installing the window, cut a length of window wrap asphalt tape that is about 4″ wider on each side than the window opening. Peel the backing and stick it to the sheathing outside right below the window so that the lower nailing flange will overlay it. With that out of the way, run a good bead of exterior window grade silicone caulk around the perimeter of the window flange just inside of the nail holes. Then with a partner, press the window into the opening and center it. Then put a nail in the top right (from the outside) of the flange into the framing. Use roofing nails for this job because of their large heads. The inside person should measure the window frame corner to corner, similar to when squaring the building. If the window is not square, the person on the outside can tweak the left side of the frame up or down to square the window. You should also measure the sides of the window frame for plumb and the bottom and top of the window for level. Tweak it around until everything looks good and then put a few more nails around the flange. Remeasure the squareness and plumb and level before fully nailing the flange.

If your windows have a built in jamb, you can use shims from the inside during the leveling process as well to help get the window in position. Since this is a garage, I didn’t sweat this too much. Next you need to cut a strip of drip cap to width and nail it on over the window. This is not needed if the window has integrated J-channels. The drip cap should be trimmed so that it is the same width as the window frame so that it doesn’t interfere with installing trim or siding later.

With the window nailed in and the drip cap on, cut some more window wrap tape and run pieces up the sides and a strip across the top. The top piece should be last and should overlap the tops of the drip cap and the side strips so any water will not get under them. The side strips should overlap the lower strip so water running down the window wrap tape doesn’t get under the lower tape. If the weather is cold and the window wrap isn’t sticking well to the sheathing, you can punch a few staples into it to hold it in place until some hot weather seals it up. Alternatively you can get a heat gun or hair dryer to heat the tape so it seals to the wall. Repeat this process for any other windows.

Entry doors are installed in a similar manner, but may have some variation depending on manufacture. Depending on the door, you may also need to apply construction adhesive or caulk underneath the door threshold or otherwise secure it to the floor or landing. In the case of a simple pre-hung steel security door you need to apply glue/caulk to the floor and threshold, caulk the integrated brick molding and nailing flange, push it in place, square and plumb the door in the opening, nail the door in place through the exterior flange, check the measurements again, and then shim the hinge side and drive screws through the hinge plates as directed by the manufacture and through the shims into the building framing for strength. Sometimes they recommend that you remove a few of the smaller hinge screws and swap them for longer deck or drywall screws that will go through shims and into the framing. Check for squareness and operation of the door. Install a handle and lockset as desired. Screws should also be driven through the door frame into the building framing and shims on the latching side of the door as well. Cut a strip of drip cap for the top of the door as well, nail it in place and then add window wrap to the sides and finally top if you have some extra around. Otherwise it is overkill.