I've often thought about this, living in hurricane country. It could be as simple as a large fiberglass septic tank- anything underground will do in a pinch. My one worry about putting it under the barn is- How do you get out if the barn collapses on top of it?

We put a cold cellar under our front porch, which we will use for wine storage and also a safe room. We used forms that were built on site for the walls. They were made of wood that clipped together. The concrete was poured into the forms to form the walls of the room. We then put a prefab concrete slab on top, that makes the floor of the porch and the ceiling of the shelter. We enter it under our stairs in the lower level, through an insulated door. Of course, the grade is up to the level of the porch, so you don't even know it is there from the front. The first photo is of the slabs waiting to be put on. The second photo has the slabs put on, with a layer of waterproof material. We poured cement over the whole thing, including the front porch to the door. The third photo is of the entrance to the room, the first door is at the landing, the further door will be the entrance to the room, an outside door.

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I also live in hurricane country just far enough north that I can consider a basement.

But no one seems to build them here. What should a simple one room, 25 X 40 basement cost if excavation is cheap? No windows.

I suppose I might have a 1/2 bathroom down there so I can lock my sisters kids down there when they visit.

It's gonna be a few years but I'm curious.

my husband and i are doing a safe room in my master closet by blocking the walls with concrete and rebar with a metal door and regualar door in front of it to conceal it. We found this to be the easiest and cheapest way. Very convienent of not having to go outside to get in the storm shelter.

Our safe room is under the porch like another poster referenced. We enter through a door in the basement. Only thing I would do differently is build a small lockable hatch door to the exterior. Concrete was already done before I thought of it. Would be nice though to have a 2nd way out.

If you don't have a basement then I like tnhousewife05's idea of the safe room in the master closet. My first thought on reading this is that I want something I could get to very quickly (without going outside) and get out of easily (thinking of the comment of the barn collapsing on the safe room).

If possible I would design it with an escape hatch/door to the exterior. Between the 2 doors you should be able to get out after the storm.

I'm guessing if something happened this might be all that remained of your home and maybe community. Knowing you have a secure locked room to live in and to protect your family would be priceless. I'd load up some supplies in this area too (bottle water, radio, batteries, blankets, canned goods, bleach, etc).

I've seen these in several new home builds lately, labelled as a "fruit room" or food storage room" off the basement. They are generally uninsulated to keep things cool in there. I'm planning on building one in when we build our house, though I feel that it might be a good idea to have a secondary "escape hatch" out, especially if you have a heavy duty door (you can buy reinforced vault doors for such applications). One idea I have read about is to use a section of culvert to go up and out and then seal it with a inside-locking manhole type cover or hatch. You could conceal it with a concrete pad and empty AC heatpump fan enclosure, so nobody sees the hatch, thinking it's a regular AC unit.

We are putting a room off our garage that is concrete and rebar reinforced and tied into the footings with rebar and with a concrete roof and with a metal door. I can get to it from inside. My dad got really mad at me until I put that into the plans!

You might google "concrete safe room" and take a look at some of the plans and ideas on the links that pop up. Might be worth comparing the cost of fiberglass shell with doing the concrete safe room inside your building space....the concrete room or closet can also serve as a fireproof storage area for valuable papers, etc.