How to Build an Above-Ground Bunker

Clear and level the site where you plan to install your bunker. Mark off the outline perimeter of your bunker and determine the height you want it to be.

Build layer upon layer of ICFs, adding rebar rods into the plastic webs of the building blocks as you build.

Make openings for doors, windows and any electrical or plumbing needs while building up the structure, using appropriate corner and closed-side ICF blocks.

Pour concrete through the blocks into the cavity between the two insulated sides, burying the rebar in the wall structure. Follow the manufacturer's recommendations for settling the concrete into the cavity. If your bunker isn't too high, you can probably pour the entire perimeter wall section in one pour, creating a strong, monolithic wall structure.

Support plywood sheets with cut 2-by-4s to the upper edge of your wall, creating a "roof plate mold." Ensure there are no gaps between the plywood mold sheets, and then pour a thin layer of concrete over them to the outside edges of your ICF perimeter. Lay down rebar rods for tensile strength. Cover them with a layer of concrete, and rake it smooth.

Purchase a suitable door (as well as any windows or other features), and mount it by drilling and bolting into the concrete inside the ICFs. With planning, you may be able to insert the mounting hardware into the concrete before it has set, saving you some drilling and mounting work. Using such techniques can provide secure access to your bunker.