Building Concrete Shelters
If you live in an area that is prone to hurricanes or tornadoes, it is likely that your home already has shelter where you and your family can stay for a short period of time. However, hurricane and tornado shelters are becoming popular in many areas where they were previously considered unnecessary due to the changing weather patterns over the last few years. Basements and other underground areas work very well, but for homes without a deep foundation or that are built on slopes, other alternatives may need to be considered.
A popular option is an interior room in the home that has been specially constructed to withstand high winds and other possible damage. These generally use concrete to provide maximum strength and durability.
A hurricane or tornado shelter should ideally have no windows and only one door. The floor, walls, and ceiling should all be solid concrete. While the shelter only needs to be big enough to contain you and your family members, the size is up to you. If you live in an area with frequent tornado or hurricane warnings, you may want some extra space due to the possibility of spending a substantial amount of time there. Hurricanes can move slowly and force you to take shelter for hours.
The walls, floor and ceiling should all be tied together using reinforcement rods that extend from one concrete slab to another. A door that is tight and extremely strong is very important. Insufficient doorways can make all other precautions irrelevant. Ideally, the door should be able to slide and lock into place, rather than operate on hinges. A hinged door can be sucked out of place by strong winds; think of any disaster movie and there is probably a scene where this happens. The door should be thick, hard wood that has been reinforced with metal on either side. When it is slid into place, it should have restraining brackets along the bottom to ensure it does not sway.
A reinforced poured concrete wall is the ideal solution for a hurricane or concrete shelter. The reinforcement bars should extend into both the floor and ceiling for maximum resistance to wind. Reinforcement also provides the tensile strength to withstand heavy objects being thrown against the walls from the side where concrete is the weakest.
However, a properly reinforced and filled block wall may also be used. A hollow block wall will not be able to withstand the forces of a major storm by itself. Block walls should be reinforced similar to a poured concrete wall, with the rebar extending into the floor slab and the ceiling. Once the wall has been built, fill all the cores with a concrete pea gravel mix. This mixture is incredibly strong and can flow through the wall to fill in any gaps. All walls should be at least 8 inches deep – the depth of a concrete block – and ceilings should be at least 4 inches thick.
The main function of a concrete shelter is to ensure the safety of you and your family. It does not need to be pretty or even to be readily apparent in your home. However, if you are very tight on space, your shelter may be able to also be used as a living space, such as a closet or even a bathroom (which would be very helpful if you are cooped up for an extended period of time). However, a dual nature may compromise the safety of the space or create additional costs. If you do decide to use the shelter for another purpose, ensure that all outlets, plumbing or other intrusions do not affect the structural integrity of the concrete. Make sure any wall fixtures or glass can be removed and secured so that they cannot become projectiles or fall during the storm.