Concrete block DIY Storm Shelter 12x20 foot

growing up I never really cared about tornadoes seemed like something that always happened to someone else my wife was the same then one day about two weeks before a wedding we got stuck in traffic and went through the edge of a tornado cell that one experience changed our thinking the next day we heard the same storm we were in and hit several of our friends so we went to help them out for a couple days we very quickly came to appreciate just how destructive which one you know can be and we decided that our family needed a storm shelter the following video shows how I built large 12 foot by 20 foot storm shelter out of concrete for less than three thousand dollars before doing the shelter I'd never laid a single brick or block or done anything with concrete I spent maybe 50 hours researching concrete and construction methods the actual construction process took about 130 man-hours spread over roughly a month I'm not an engineer but did consult with engineers and what I built you are responsible for what you build and I recommend getting the assistance in the structural engineer this video shows you how I built my shelter and should save you from having to do all the research I did here will my goals for my shelter it had to fit everyone various groups like FEMA recommend 10 square feet per person in a storm shelter this is a good starting point and I wanted room for at least 10 people in my storm shelter the storm shelter also had to be comfortable when you can hear or see a tornado there probably is no longer time to run your storm shelter so a safe policy with tornadoes is to take cover when there's a tornado warning if the storm shelter is a moldy spider hole no one is going to want to go there for a stupid tornado warning your shelter may give you security in theory but not in practice the storm shelter has to last a long time and be safe and it has to be economical once I had my design requirements I did a little shopping around for pre-built options but the cheapest options are usually around $3500 for only enough room for three or four people 30 to 40 square feet larger options rapidly go up in price to twenty thirty thousand dollars these shelters may be very nice but there was no way I could afford one of the larger units as von Clausewitz said the greatest enemy of a good plan is the dream of a perfect plan there's just no way I can afford something like that waiting for something like that would keep me from ever having a strong shelter some people advocate using new septic tanks as a cheap storm shelter so I looked into that a very big septic tank is about 2,000 gallons but those are only 6 by 10 feet 60 square feet and when I price one it was several thousand dollars plus installation also they aren't very accessible they're not designed for people to get into them and out of them so I scratched the septic tank idea another idea I read about online is to use a huge concrete culvert pipe and just close up the ends but I didn't even bother getting quotes on that I had recently priced some small 18-inch covert pipe and that alone was prohibitively expensive once I realized all the pre-built options were quite expensive I started looking into building a shelter from scratch when it comes to building a wall concrete blocks are incredibly cheap strong and long-lasting a regular concrete block costs about a dollar and is roughly eight inches by eight inches by 16 inches this means that a wall that is six feet tall and ten feet long only uses about 70 blocks that's only $70 not counting mortar I worked up an Excel spreadsheet that allowed me to punch in various shelter sizes and see what the blocks would cost I found that an 8 by 8 shelter would use about 240 blocks but a huge 12 by 20 used only twice as many about 480 that's less than half the price per square foot at least for the walls I suspected that the best way to do the floor and ceiling was poured concrete so I went and started researching it the first thing I learned was that concrete is heavy its measured in yards a cube three feet to his side is a yard one yard of concrete weighs roughly 4,000 pounds and concrete doesn't get lighter as it hardens that's the second thing I learned the concrete that you pour is made up of basically three components Portland cement aggregate and water after the concrete stops moving it starts to cure a chemical reaction known as hydration and causes the Portland cement and water to bond the water stays in your slab but it's not water anymore so when you pour four thousand pounds of wet concrete a month later after it is cured it will still weigh roughly four thousand pounds the third thing I learned is that I was going to need a lot of concrete footers in a slab for a 12 by 20 structure would be about five yards that's about 200 bags of quikrete that weigh 80 pounds each that's a lot of mixing so I started looking for concrete truck prices if you search Ready Mix you can probably find a few places within an hour's drive of where you live where I live a yard of 3,000 psi concrete costs about 80 bucks but I had to get five yards or pay delivery fees prices and minimum vary from company to company and region to region one of the limitations of a concrete roof is the distance you can span I determined that I could comfortably span 12 feet a friend in the church had a digger and was in the area so I had him dig a hole for the shelter he dug it about 19 feet into the hill and about 14 feet wide in retrospect we should have made the hole a little wider this would have made some of the construction work easier I wanted the floor to end up just above ground level so this dictated how deep we excavated it took him about eight hours to dig the hole and cost me $300 once the hole was dug we had to build the formwork and get ready for the pour the American concrete Institute recommends as a bare minimum a footer that is eight inches deep and 16 inches wide the center of the concrete block goes at the center of the 16 inch footer the purpose of the footer is twofold to create a smooth level foundation to build on and also to transfer the weight of the structure to the dirt beneath it if you are building on soft soil you may need to make your footers wider my slab floor was going to be about four inches thick the forum boards are used to hold the poured concrete and to level the slab when you screed when you build your forms you want to make sure that you are very close to square and perfectly level I can't stress this enough on my shelter we had two spots where the slab was slightly out of level maybe a quarter inch over six feet and this caused a lot of problems with laying the blocks on top after you have your forum boards in place you need to calculate the volume of your form when I calculated my volume it came out to about six yards so I took some buckets and measured out roughly a yard of gravel which I scattered around I still ordered six yards of concrete but now I had a surplus of concrete coming which is a good idea if you run out of concrete before your forms are full you are in trouble you don't get the strength you need with that shallow depth and adding a few more inches later isn't the same coming up short on your pour is very bad order extra concrete you will also want to add some rebar I'll explain more about rebar and concrete later on I use two pieces of number four rebar all the way around lift it off the ground at least three inches concrete provides protection against water in the ground leaching in and rusting the rebar you want at least three inches of cover on rebar where the concrete is in contact with the soil if rebar inside your slab rusts it creates pressure that can cause spalling and cracking which seriously compromises the strength of this lab I ordered six yards of concrete and I asked that they upgrade the mix to 4,000 psi and add fibers this brought the cost up to $99 per yard plus tax the truck came and proceeded to fill the forms now most concrete trucks allow a certain amount of time to unload if you have to unload slower than that they may start charging you by the minute so you want to be able to work pretty fast what you need to do is level the concrete out and then screed and float it to create a smooth level surface what you've just seen is the first eight and a half minutes of the storm shelter video that I created the full video is over 20 minutes long so you've only seen less than half of it the rest of the video contains information on building with concrete block building formwork pouring the concrete roof designing the rebar grid and adding doors and other things to the shelter the rest of the video is available at DIY storm shelter com

Channel: David Botkin

Views: 2,490,983

Keywords: concrete, construction, storm shelter, tornado shelter, fallout shelter, diy

Id: 0tsqK5pbxcs

Length: 9min 13sec (553 seconds)

Published: Sat Oct 13 2012