Tornado/Storm Shelter - Underground

[jigs_n_fixtures]

FEMA is a good starting place.

The Forest Service, Forest Products Lab, has several designs for wooden storm shelters. The design intent was that they be built as add-ons or built-ins for existing structures.

Search USDA Storm Shelter.

Natural Resource Conservation Service, used to have several plan sets available.

And, the Concrete Masonry Association used to have designs for CMU storm shelters. Either above or below ground.

What type of design you want is probably highly dependent on how hard it is to dig where you are. Selecting an underground structure somewhere the digging is hard doesn't make sense.

If you're going underground a metal arch culvert with a CMU end wall might make sense.

And most state highway agencies have standard plans for reinforced concrete box culverts available for download.

 

[drumminj]

FEMA is a good starting place.

The Forest Service, Forest Products Lab, has several designs for wooden storm shelters. The design intent was that they be built as add-ons or built-ins for existing structures.

Search USDA Storm Shelter.

A company called HabiFrame offered a wood storm shelter. I don't know if they're still in business, but we had wanted to go with them but couldn't get the needed materials (during COVID times)

 

[EddieWalker]

Early this week we had two confirmed tornadoes in my area. Both were far enough away to not worry me while they where happening, and nobody was hurt by either of them, but it's always a concern.

There is a place just North of Tyler that has a bunch of preformed underground shelters for sale that look like they are fiberglass. I've never stopped or looked at them, it just seems odd that they look more like swimming pools then something to hide from a tornado it. I'm guessing that the dirt is where all the protection is and the fiberglass just keeps you dry.

I have two clients with concrete shelters that are right outside their back doors. In the entire time that they have lived in their homes, they have never gone into those things when a storm is coming. Here, that usually happens at night, and sometimes after midnight. It's dark, windy, storming with heavy rain and even lightning. Nobody is leaving a dry house to go out there unless it's at the last minute.

I saw a video of one being installed in the floor of a garage. That made more sense then outside.

I also so where they built one in the corner of a garage. I thought about doing that, but decided to build a new master closet and make it into a storm shelter based on FEMA plans.

FEMA P-320 Safe Room Design CMU Plans and Details | Building America Solution Center

basc.pnnl.gov

I have a few clients with their master closet being a storm shelter and it makes a lot of sense to me. It's the easiest place to get to if you are in bed. It's also used every day as a closet. The actual build doesn't look too hard, just follow the instructions and take the time to do it right.

 

[Ghost River Retrievers]

Early this week we had two confirmed tornadoes in my area. Both were far enough away to not worry me while they where happening, and nobody was hurt by either of them, but it's always a concern.

There is a place just North of Tyler that has a bunch of preformed underground shelters for sale that look like they are fiberglass. I've never stopped or looked at them, it just seems odd that they look more like swimming pools then something to hide from a tornado it. I'm guessing that the dirt is where all the protection is and the fiberglass just keeps you dry.

I have two clients with concrete shelters that are right outside their back doors. In the entire time that they have lived in their homes, they have never gone into those things when a storm is coming. Here, that usually happens at night, and sometimes after midnight. It's dark, windy, storming with heavy rain and even lightning. Nobody is leaving a dry house to go out there unless it's at the last minute.

I saw a video of one being installed in the floor of a garage. That made more sense then outside.

I also so where they built one in the corner of a garage. I thought about doing that, but decided to build a new master closet and make it into a storm shelter based on FEMA plans.

FEMA P-320 Safe Room Design CMU Plans and Details | Building America Solution Center

basc.pnnl.gov

I have a few clients with their master closet being a storm shelter and it makes a lot of sense to me. It's the easiest place to get to if you are in bed. It's also used every day as a closet. The actual build doesn't look too hard, just follow the instructions and take the time to do it right.

An underground shelter, whether concrete, wood, fiberglass, etc. just seems safer to me (but I'm sure the above-ground shelters are equally safe) ... plus there's the aesthetics factor.

My house is on a conventional foundation, not a slab. Would a "closet shelter" be possible in the absence of a slab to secure it to?

I have detached garage (close to the house), but I'm not sure it's big enough for either a door-in-the-floor to be unencumbered by a car or a safe-room in the corner. Of course, when there's plenty of warning, I could tell my wife to move her car out of the way (just kidding ... wouldn't happen anyway).

I appreciate all the suggestions!

 

[drumminj]

I thought about doing that, but decided to build a new master closet and make it into a storm shelter based on FEMA plans.

This is what we did, but with 6" poured walls. In our floorplan it can function as a closet for our downstairs master if we ever move down there, but for now it's just the "tornado room."

It's nice to have a place that's comfortable and we don't mind going into when the weather radio goes off.

@Ghost River Retrievers we have a crawl space vs being built on a slab, but did have to have special footings/foundation for the safe room. Ideally your safe room isn't connected to the main framing of the house at all -- this way in a tornado there's no part of the house attached to act as a sail and damage or topple the safe room as it blows away. I'm not sure about retrofit options there but I suspect there's a way to make it work.

 

[CPTKILLER]

https://www.fema.gov/sites/default/files/documents/fema_rsl_fema-p-361-safe-rooms-for-tornadoes-and-hurricanes_042025.pdf

This can be useful.

 

[EddieWalker]

I just scrolled through the FEMA link and really like how much information they provide. There didn't include any plans on how to build the room, but one of the things that caught my eye when looking at the requirements for rebar size and spacing in a cinder block wall had this in it.

"can withstand the tornado test missile"

For some reason, I found this line to be funny.

 

[gstrom99]

My house is on a conventional foundation, not a slab. Would a "closet shelter" be possible in the absence of a slab to secure it to?
I appreciate all the suggestions!

Have a pic of your house? Basement or crawl space? Access from inside the house is ideal. I'd look into digging out a spot for one of the pre-fab units, right next to the house.

I have a basement, but I've seen build "safe" rooms/structure built in the basements, to protect us from the house collapsing down on us. For me, I go down there and under the stairs.

I was told by a guy that stopped by last year (my age) who grew up in this old farmhouse, that they HAND DUG the basement under the existing house (in the 1960's I think), so it CAN be dug down and put under your house.

 

[EddieWalker]

From what I understand, there are two concerns with a tornado. Flying debris, and uplift.

To handle the flying debris, the walls have to be strong enough to resist impact. Since the tornado can have winds from 80mph up to 120 or more, those walls have to be pretty strong. Burying it in the ground is the best option for this. For me, the best way to build above ground is cinder blocks with rebar and concrete. I've never seen a prefab metal one like they sell at Lowes that I would feel safe in.

The second issue, is keeping it in place. All the FEMA plans that I've looked at require massive footings. Ideally it should be all part of the foundation with rebar bending at the bottom so the rebar isn't pulled out of the concrete. For me, I'm cutting a trench in my concrete slab, digging under the slab and bending the rebar so it's shaped like an L that's going to a massive footing that I'll dig out. Then the rebar goes up through the block and bends over for the ceiling. One stick for each run that goes under the slab and forms the ceiling.

If I had a pier and beam floor in my house, I would remove the floor and start digging into the ground. My thought is to make it like a brick fireplace foundation and build it up from there. If my wife is in there when a tornado hits, I do not want to risk cutting any corners. The cost of concrete and rebar is minimal compared to the labor involved, but overall, the labor is just time and effort that will get done eventually once it gets started.

 

[grsthegreat]

I'm sure you can build one, but what's your time and money worth? I have a backhoe, so I dug my own hole to their specifications. They just drove up and dropped it in the hole. I think I paid $4000.

Mine is one of the sloped front concrete models, like this.
View attachment 3432594

I always wondered, what happens if debris covers door. How do you get out?