When you convert a shipping container into a storage unit, workshop, home, and other structure that you need to move in and out of on a regular basis; it may be more convenient to install a man door in your shipping container than to use the factory steel doors on either end of the unit. A frame door is smaller, lighter weight, and easier to manage than the traditional swinging doors of a shipping container.
Keep in mind that installing a man door into a shipping container requires several commercial tools and pieces of equipment. It is recommended that this type of project be undertaken by a professional.
To start, you'll need an angle grinder or oxy-acetylene torch, a tape measure, metal file, magic marker, 2x2 square steel tubing (enough to frame out the opening you cut, relative to the size of the door), the door that you would like to install, clamps, industrial door sealant, and a welding kit.
Begin by measuring and marking the area that where the door will be placed. It's important to make sure to include additional space for the steel frame/tubing.
With the area for the door marked off, use the angle grinder or oxy-acetylene torch to cut the opening. If you're using a torch and your container is still painted, the outline that you made may melt off as the torch burns the paint. Should this happen you'll need to remove the paint prior to drawing your outline.
Once the opening has been cut and you've allowed the steel to cool, use a metal file to remove any sharp edges or burrs that may be been created during the cutting process.
The next step is making the door frame. Cut three pieces of the tubing to correct height for the two sides of the frame and the header. Square up the frame and clamp everything into place so that it remains square while you weld the corners. While it's not structurally necessary, some people tack weld a piece of rebar across the footer or open end of the frame to keep the frame square while it is installed.
With the frame assembled, place it in the opening and level the header of the frame so that your doorway is square. Once assured that the frame is square tack weld the top and sides so that it's secured in the opening. Again, if there are any sharp edges or burrs left from the welding, use the metal file or angel grinder to remove them.
To weather proof the new door frame, apply the sealant to all openings between the door frame and container shell. If any openings are missed it may allow for a draft, moisture, or even unwanted insects to gain access.
With the steel frame welded square into place in your shipping container, the final step is to install the door. Each door is unique, so thoroughly read, understand, and follow the instructions included by the manufacturer of the door.