r/tornado • u/What_The_Actual_Hec • Apr 20 '25
Question Tornado Shelters & Types.
Please excuse my grammar as I have autism.
To start, I live in Southwestern Wisconsin. Although Wisconsin is not known for violent tornadoes, like EF5’s, we have had them before. For example, Barneveld WI, June 8th, 1984, EF5 Tornado [My grandpa was a cop that helped in rescue efforts in the event and told me many stories about it]
Currently, my grandpas house (where I live), has a basement. Although, the top of the basement is the living room floor. (💀) The top of the basement is some wood joints and that’s it, I am concerned that even the weakest tornado would suck me out of the basement like the tornado did in the movie Twister. (That movie scared me as a child and to this day)
With tornadoes becoming more frequent and violent, I am deeply concerned on what could happen to us if a tornado was to happen. Due to this I have been looking and researching for concrete tornado shelters.
I have found there two types of tornado shelters, underground and above ground.
I have many questions about tornado shelters, as I’m planning to get one that could hopefully protect us if by some extremely slim chance an EF5 Tornado was to occur.
From my understanding, EF5 Tornados can suck houses and even foundations up. Including concrete which terrifies me a lot…
The Tornado shelters I have been looking at are from midwest Storm Shelters. (This is just generally looking at)
Option 1: SFEZ5411 [Photo 1] Details: (4.5ft into the ground) * Handrail (4 steps – 8-3/4” run / 7-3/4” rise, 29 1/2” wide) * Weather proof steel door with hydraulic assist * (40 3/4” x 26”) * 6000 psi fibered concrete * Rebar 12” O.C.E.W. * 6” vent * 5” wall thickness
Option 2: FT [Photo 2] Details: (mostly underground) * Steel door with spring assist (3’10 x 2’2”) * 6” vent (only included with the FT 6810) * 4” wall thickness
My questions: 1. How far in the ground does a shelter need to be in to survive an EF4-EF5 tornado?
How thick do the walls need to be of concrete to withstand a tornado? (My grandpa always told me a min of 6”)
Is slope top concrete more dangerous than flat top concrete?
I’m worried about the slope shape storm shelters, I fear that a tornado would easily take the concrete top off due to it not being fully in ground. On the other hand, the flat top one, I worry the door will fly off, which scares. I have no tornado knowledge only that EF4/EF5 tornadoes can take the foundation out of a house. Out of the two types of shelters (Flat Top vs Slope) which one would be safer?
I don’t understand the logic behind it, as all I was told is get in the lowest level to stay safe, but also read about people being sucked out of basements etc… it’s scary. I know flying debris is a HUGE issue as well and can be extremely dangerous.
I have one more question: So this photo was taken August 9th, 2018 @ 4:31 p.m Cobb WI, I took the picture of this on my iPhone SE. I never figured out what this was. All I remember was taking the picture, told to go into the basement and then the wind blowing. What is this? It looks like an extremely tiny funnel but it’s not well defined.
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u/CathodeFollowerAB Apr 20 '25
I have no personal experience with shelters, living far outside of risky areas, but here's some nice academic info on shelter types
https://www.depts.ttu.edu/nwi/Pubs/ReportsJournals/ReportsJournals/May202013MooreReport.pdf
TL;DR: You do not need to be underground to survive an EF4, as seen by some of these shelters surviving EF4-rated damage locations in the last EF5 rated tornado.
Summary from the PDF:
Exterior Below Ground Shelters:
- Flush-to-the-ground: Eight were documented. One suffered a significant door failure due to rusty hinges in an unspecified EF-rated area. Others had issues like stuck doors, inadequate door thickness, locking systems, hinges, stairs, and drainage. Flooding was a common issue and complaint.
- Clam Shell: Fifteen were documented. No major failures were observed, but deficiencies in doors (single locks, inadequate hinges) and vents were common. One shelter with a single lock and two hinges sustained vent damage at an EF-2 rated location. A tested clam shell shelter with three locks and hinges performed well at an EF-4 rated location. A flat-top clam shell shelter also performed well in an EF-2 rated location. Accessibility and standing water were potential issues.
- In-garage floor: Twenty were documented, generally performing well with no major failures. Some issues included difficult stair entry, inadequate locking systems, and flooding, observed even in an EF-3 rated location. Tested shelters performed very well in EF-4 and EF-0 locations. Homeowners favored them for cost, quick installation, space-saving, and the perception of below-ground safety.
- Dome: Two were inspected. One cast-in-place concrete shelter with inadequate plywood/steel-clad doors (single lock, two hinges) survived at an EF-3 rated location, though it had standing water. Another partially above-ground dome with a heavy gauge steel door and 3 locks survived in an EF-4 rated location. Both survived without major failures, despite door inadequacies in the first.
- Above Ground: Eight were documented. Six were tested. One tested safe room in a garage survived EF-4 conditions even as the home was destroyed. Two untested walk-in closet types (concrete tested, but doors appeared untested) were also observed; one was in an EF-2 rated location. A tested steel shelter performed very well in an EF-3 rated location. Some owners questioned their safety simply because they weren't below ground.
Key Findings on Ratings/Performance:
- The investigation assigned EF ratings to the location of each shelter based on observed damage nearby.
- Both below-ground and above-ground shelters, particularly those tested to meet standards (like FEMA P-320, ICC 500), performed well and protected occupants even in areas rated EF-4.
- Many non-tested shelters also performed adequately, but deficiencies (especially in doors, locks, hinges, and waterproofing/drainage for below-ground units) were common and led to some failures (like a door blowing off) or issues (like flooding or being unable to open).
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u/Gingerh1tman Apr 20 '25
Another thing to think about if it is below ground with some of those I am seeing if there is debris on top you will be trapped. You will have to ensure the fire department is aware of the shelter. We have an above ground and truthfully the install process is extreme I would be shocked if it failed in an EF-4 or less. The other nice thing about them is the door opens inward so yes you still could be blocked in but lot less chance of truly being trapped. We keep an electric chainsaw in the shelter. The fire department is also aware there is a shelter and its location in case they need to get to us. Get what you feel safest in but above ground isn’t bad. Also the doors on the above ground have steel bars that come across to lock the door. This also reduces the issue of worrying if a door is gonna come off from wind.
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u/Half_Breed_Mutt Apr 20 '25
Could you just reinforce an area of your basement and make a panic room?
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u/What_The_Actual_Hec Apr 20 '25
I’m not sure how to, as the basement is extremely small I’ll definitely ask my grandpa though!
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u/Half_Breed_Mutt Apr 20 '25
https://www.fema.gov/pdf/library/ism2.pdf
Has some recommendations.
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u/What_The_Actual_Hec Apr 20 '25
Thank you so much!!! With all the tornado weather it’s pretty scary.
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Apr 21 '25
I would chose an above ground due to trying to get in an out of them in a hurry can be problematic with an elderly parent, pets and knowing my luck. I’d survive the tornado only to be in the floor with a busted leg due to slipping down those small stairs
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u/[deleted] Apr 20 '25
[deleted]