Question:
Can I install an above ground safe room in my home with a crawl space?
Answer:
First, let’s define the general types of residential construction:
- Slab on grade: A concrete slab is poured in a properly prepared area with the slab sitting directly on the ground. It is often designed to be thicker around the perimeter to support the weight of the walls. Walls and structure are fastened directly to the concrete floor.
- Raised floor: Also known as crawl space, pier and beam, footer and stem wall. Wooden floor joists and decking are built on top of concrete piers and stem wall, with an air space between the soil and the floor. The raised floor, stem wall and piers provide support for the walls and a “crawl space” underneath.
- Basement: A combination of slab and raised floor construction, with the slab poured far enough below grade to allow walking height space between the slab below and floor joists above.
- Modular or Mobile Homes: Wooden floors and structure are built on top of steel I-beams suitable for over the road transportation. The I-beams are typically set on concrete blocks or piers.
Of the four types of construction listed above, and assuming building codes were followed, only the slab on grade method provides an adequate base throughout the structure on which to anchor a safe room.
However, there are exceptions and alternate location possibilities:
- Homes with basements are candidates for indoor safe rooms as long as the installation is limited to the concrete basement floor; or
- An adequate slab can be found elsewhere, such as a garage floor, driveway, carport, patio, or shop floor; or
- A slab or base engineered specifically for that purpose is installed.
So to summarize, a safe room can be installed on any standard reinforced concrete slab or base of adequate mass and geometry, indoors or outdoors. It can NOT be installed on a raised floor, but there are many other alternate locations with concrete that may qualify.
Check out my next blog for general guidelines to qualify a concrete structure for use as a safe room base, and how to save money with a DIY safe room slab project!