Tornado/Storm Shelter - Underground

[Ghost River Retrievers]

It seems that we are now in "tornado alley." Last month a series of tornadoes tore through our area, with massive destruction and loss of life. One came within a mile from our home.
It's time for me to seriously consider constructing a shelter for people (and a few dogs). Probably around 100 sq. ft. will provide the space we need. Due to my wife's concerns about appearance, it needs to be underground (frankly, those seem safer to me anyway).
Have any of y'all build an underground shelter ... or had one built?
I've looked at the pre-fab shelters and they're pretty pricey, even without installation, which is why I'm considering building one or contracting for one to be built.
Factors that I know to be conscious of:
* level of the groundwater
* sturdy door
* ventilation
* lighting (I may put a generator in a hole nearby which could be used for electricity if necessary)
If built for lengthy storm:
* storage for a little food & water
* potty

I appreciate any thoughts, particularly (but not limited to) those from folks who have underground shelters.

Thanks,
GRR

 

[bcp]

Due to my wife's concerns about appearance, ....

Your wife probably wouldn't go for the increasingly popular idea of burying an old school bus.

buried school bus shelter - Google Search

Neither would I.


Maybe start with prefab box culverts.

prefab box culverts - Google Search

Bruce

 

[redman135]

Would it pay to setup for overnight stays so you can sleep easy? In the event of a tornado warning for night time.

 

[oldnslo]

Do you have the option to put something in a side hill or is your ground flat? I have never built one but have seen several side hill dug out root cellars that double as storm shelters.

 

[LittleBittyBigJohn]

We are in tornado alley also. There were a couple of deadly tornadoes in 2011 and 2014 where I'm from. I have been fortunate enough that I was able to build a safe room into our house. It's above ground and easily accessible.

Typically shelters are used for a short time. I personally don't see the need for provisions or a toilet. Generally around here you watch the news or listen to the radio and if one is getting close you may go in the shelter for a few min to let that round pass. For light most people will either get by with a flash light or have solar landscaping lights nearby to just grab on the way down.

When you are thinking about location, remember you will likely be in a hurry, it will usually be dark, wet and raining. If it's too far you won't want to deal with the hassle and inconvenience of getting to it. That in mind a popular shelter that people install is flush mount in the floor of the garage. They are handy because you don't have to go out in the rain to get in them. But you have to make sure there is not a car parked to where you can't get in the door if you need to get in.

I noticed on your list you noted a "sturdy door". Please don't use a sturdy door. Use a Shelter door that is installed correctly. There was a family in a shelter that died because the sturdy door was ripped off the shelter and the family was sucked out by the tornado and were killed.

Ground water is just something you will have to deal with. Most are sealed pretty well at installation but will eventually either leak from the ground water seeping in or from rain coming in the door or vents. The installers will add a type of anchor strap that is designed to keep the unit from floating out of the ground if the water table gets too high.

 

[gsganzer]

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.

 

[MossRoad]

Just be sure you have a way of opening the door if something large falls on it. Like a very, very large hydraulic jack.

If you have an inward opening door, something heavy can put enough pressure on it so that the locking mechanism can get jammed. It doesn't take much.

If it's an outward opening door, that's self explanatory should something heavy fall over it.

My father built a bomb shelter in his basement back in the 50s (The Russians are gonna bomb us). It was all concrete with a concrete reinforced ceiling. It had a 4x8 wooden trap door that he eventually was going to replace with a cement slab door with dual hydraulic rams and a hand pump to open it but never did. It was large enough that you could go around a corner quite a ways and be out of the way if anything collapsed the trap door and stairs.

We spent many a time in that shelter during tornadoes. And when you're down in that hole, it's really quiet. And then the lights go out. And then every kid flicks on a flashlight and dad tells them all to save their batteries and we only use one at a time. Good memories.

Just be sure that if you go the underground route it has adequate drainage should you have a major flood event. Perhaps even a dike wall around the entrance should a flash flood come from a neighbor's property. And adequate ventilation.... that would be more than one source.

I'd just keep some comfortable seating or benches to rest on, a few gallons of water per person, some emergency blankets, and some flashlights with spare batteries. A radio would be nice if cell service died.

Good luck in your planning.

 

[Blue Mule]

Here in KY, underground shelters begin at about $5,000 INSTALLED and go up from there depending on how many people you want it to be able to hold. I doubt you can build your own for that price. So I would strongly suggest looking into a pre-fab and pre-engineered solution like so many companies offer these days. Also, there are some that they install under your garage floor. That way you don't have to run outside in the weather when the tornado warning is issued.

As far as the door goes, what people do around here is notify the local authorities that you have a storm shelter and they put you on a list. That way if there ever is a tornado they know to come look for you and if your shelter door is blocked rescuers outside will free you. To me the door would be a minor concern, as the companies selling these shelters have already done their homework.

 

[drumminj]

If you haven't seen it before, check out FEMA P-361 and P-320 documents on tornado shelter construction. It's focused on above-ground designs if I remember correctly, but does discuss necessary ventilation and such.

 

[MossRoad]

If you haven't seen it before, check out FEMA P-361 and P-320 documents on tornado shelter construction. It's focused on above-ground designs if I remember correctly, but does discuss necessary ventilation and such.

Yep...

Safe Room Publications and Resources

The free safe room resources listed below have been developed by FEMA's Building Science Branch.

www.fema.gov

https://www.fema.gov/sites/default/files/documents/fema_safe-rooms-for-tornadoes-and-hurricanes_p-361.pdf

 

[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?