How to Build a Cinder Block Bunker

Spray paint the outline of the 6-foot by 6-foot perimeter where you'll build the bunker. Know that any grass within the area will be killed either by the pressure of the cinder blocks or by being denied sunlight. Put this bunker in a place where you don't mind killing the grass.

Lay out the perimeter of cinder blocks, with the open sides facing the ground. Leave a four-block gap for the door. Mix cement in a bucket with a trowel by adding the proportion of water listed on the bag, then mixing in a figure-eight pattern. Apply the cement to the top of the blocks and stack more cinder blocks on top, pressing the new blocks firmly into the cement. Orient the blocks so the open sides are facing up, the solid sides facing the inside and outside of the bunker. The long side of the blocks should be running parallel with the perimeter of the bunker. Stagger the layers of blocks so the seam between the lower line of blocks is in the middle of a block on the next higher layer. Stack up blocks until the bunker is 7 feet tall.

Cut four 2-by-4 boards to 8 feet long with the circular saw. Lay the boards evenly spaced across the top of the bunker, parallel to the door opening. Drill through the boards, into the cinder blocks, using a bit that's slightly narrower than the masonry screws you'll use later. Put masonry screws into these holes, tightening them into place. Put in two screws at either end of each 2-by-4 board.

Cut a plywood sheet to 8-feet by 8-feet. Nail it into the 2-by-4 frame by hammering nails through the plywood, into the boards. Put in two nails every 3 feet where the plywood touches the frame. Seal the plywood with a decking sealant made to prevent water damage by applying the sealant with a brush. Brush sealant onto any exposed parts of the 2-by-4 boards and the plywood ceiling inside the bunker. Apply two coats of sealant to be certain the wood is completely sealed.