How Big Should a Safe Room Be?

When families start planning a safe room, the size question comes up almost immediately. The honest answer is that it depends on who will be inside during a tornado warning. Here is how we walk Kansas City families through it.

Start with the people, not the house

A safe room is sized by occupancy. FEMA guidance and the ICC 500 standard set a minimum floor area per person, and it goes up when someone uses a wheelchair or cannot sit or stand comfortably. So the first step is a headcount. Count everyone who lives in the home, then think about grandparents, visiting family, and neighbors who might run over when the sirens go.

Plan for the worst night, not the average one

Most families size for their household and then add a cushion. A tornado warning at 2 a.m. in April with the kids home and a grandparent staying over is the night to plan for. It is far easier to build a little larger at the start than to wish you had. Pets count too, and so do a few supplies like water, a flashlight, a radio, and shoes.

Size affects where it can go

A larger room needs a bigger footprint. In an existing home, a garage floor or a basement corner may limit what fits, and an in-ground unit under the garage has different constraints than an above-ground room built inside. Our above-ground safe rooms and in-ground storm shelters pages explain how each style handles space and access.

Stay with a rated design

Whatever size you choose, the shelter should be designed and built to FEMA P-361 and ICC 500 criteria. Rating matters more than size, because a big room that is not built to resist tornado wind and debris is just a closet. We covered the rating side in our post on how storm shelters are rated.

Frequently asked questions