Gather the materials and tools needed for the storm shelter including reinforced concrete blocks, concrete mix, shovels and trowel. Dig a large hole in the ground at the desired location for the shelter. Use the concrete blocks to build the main walls of the storm shelter. Add ventilation slots to ensure oxygen can reach the storm shelter interior in case debris falls on the structure during a storm.
To seal the shelter and add stability, use concrete mix to lock the reinforced concrete blocks into place as well as cover them and fill in any cracks. For added sturdiness and insulation, use dry wall or ply board in addition to the concrete blocks. Screw the lumber into place to secure this insulation into the structure.
Measure the distance from the walls, and calculate the weight of the concrete roof to ensure the roof of the structure has enough support. If the walls are not supportive enough for the weight of the heavy-duty roof, add support beams. Typically, metal support beams work well and are easily added to or against the concrete block walls. Leave room for a door in one of the shelter walls, or add a hole in the roof where a latch can open to the outside.