From Whisper on our forum
Shelters, My favorite subject. I wanted to write something about stacked concrete block Shelters, insulation and water myths. You don’t have to be an expert to build a dry stacked concrete block shelter yourself. The hardest thing would be pouring a footing, which you can either read about how to do this or pay someone.
The way it works is simple compared to other building methods. The web site listed at the bottom of the post recommend using mortar on the first row or two in case the footing isn’t level. The rest you simply stack at your own pace, no mortar between the joints. After you start stacking, just use a level to make sure they are going up straight. Then pour your concrete down the center cores with rebar as you go. Check out the site, there’s pics and more details.
Here are some of the nice things about it. First off, after reading dozens of books on underground homes, green building, corn cob homes, straw bail, rammed earth, earth bags, cord wood…… one of the many things I learned is the worst way to build a home is with wood for many reasons. But the most important one being mass. Energy is stored in mass, whether it’s hot or cool. This is why the best material is concrete (although log cabins have mass because they are so thick, you can’t really insulate them correctly without loosing the log cabin look…). Concrete is the best material for holding mass although some may argue that rammed earth or earth bags are as effective. I go along with the concrete people.
The second thing that I learned is all about insulating a home/shelter. If you ever heard the term “super insulated home” this is where it came from. Without the insulation, the mass is useless. We have been doing it wrong for the last 100 years! This will be shocking to read if you haven’t read it before. All your insulation should be on the outside of your home only. This is whether you are going to build above ground or below. This is also not an opinion but a fact proven by studies at universities. The way it work is simple. If you are producing heat or cool air, the insulation on the outside of the house holds it in. I have read results in the past that stated, if you had insulation on both the inside and outside, it wouldn’t be nearly as efficient. I think the best book that I read about it was by the university of Minnesota. But it’s packed somewhere.
There have been some myths out on the internet about water and or moisture problems building an underground concrete shelters. Well yeah that’s true if you don’t water proof it. There are many products out there to do this. I wouldn’t go with drylock alone on the outside of an underground shelter. I probably wouldn’t use it at all. I’ve seen it peal. I also had an underground bomb shelter in my last house. It came with the house. I used drylock on the tunnel. It didn’t work. I think tar may be the cheapest thing to use, but I know there are far superior products out there.
If you are thinking of building an underground shelter then you have to decide what are you preparing for? Is it to hide? If that’s the case then you could go with those underground fiberglass things. In my opinion, that’s all there good for. Those companies have spread some of the misconceptions about concrete shelters having water problems. If you want a shelter that can withstand earthquakes, bombs, nuclear fallout or what ever else, concrete is the only way to go. Before you disagree, ask yourself this. How many countries have you heard about making underground shelters out of fiberglass? Give up? The answer is none! (at least that I heard of) OK, how many countries have you heard of that are building underground concrete shelters? Answer: Out of all the countries that I heard about…. All of them. Hmmmm There must be something to it.
OK, I wrote all that to lead up to what I am planning for next year when I move. I plan on building an underground concrete shelter using stacked concrete block. My plan, at this point, unless someone can convince me otherwise, is to have two walls of dried stacked concrete block walls, which I will drill holes in the blocks to connect rebar to both the inside and outside walls. Then pour concrete in-between.
I hope people picked up something on this long winded post. Please share your thoughts on this.