More Insulating Concrete Form

I had lots of questions from my post on Tuesday, so I thought I’d answer them in a post so others can find the answers quicker.


what material is used to hold back the concrete for the ceiling itself? steel? foam? could you do the job with “pre stressed” concrete precast panels?

when you pour the side walls, how high can you go in one pour, without additional bracing around the ICFs?

The ceiling was held up for the pour by plywood and insulation panels. Once dry, the plywood (and 2×4 bracings) were taken away, and the insulation panels were left up.  I can’t remember if those panels were just painted with ceiling paint, or whether we did some ceiling drywall.

I know nothing about pre-stressed concrete precast panels. I would say you’d need to refer to engineering specs for the panels, and compare those specs to what you need in terms of spans between support and weight bearing requirements.

Side walls, experienced crews with top of the line equipment can go 14 feet in one pour with minimal bracing. Regional crews without all the fancy (expensive) gear can pour an 8-10 foot wall in one pour, no problem.  (Or they should, be wary if yours can’t.) The bracing required for a wall is shown to the right. If you are doing a multistory house, pour the walls, then install the flooring, and then begin the process again.

child of Odin

As always, this is my favorite blog. … First, do you have pics of the finished product? My wife is not a prepper, and not interested in “alternative” building techniques unless thy look normal. Pics could help convince her. Second question: how does this compare, price wise, with conventional building methods? Third: you use a crew, but how DIY friendly is it.


Glad to hear we’re your favorite!

I don’t have public pics of the doomstead. I’m a little paranoid about how easy it can be to use images on the web to find places/people.  Plus, I don’t know if I’d call it finished. It’s getting a lot closer, and there have been people living in it for a couple of years now, but it’s definitely still a work in progress.

ICF houses can look like hobbit holes, or they can look like mansions. It all depends on how they are designed.  I wouldn’t try to DIY one of the mansion ones, but hobbit holes are very friendly for non-professionals.  Check out this picture from the company we used for materials. Quad-lock.

They still need to put on some exterior finishing, like a siding or brick, but it has windows and doors and when finished will likely look like any other nice home.

Most builders put building costs at 6-8% above conventional building.

On one hand it’s very DIY friendly.  It’s easy to design with, and the forms are easy to put together.  But, you have to be careful about the pouring; between bracing, vibrating out bubbles and slowing the pour from the pump truck, it can be intimidating if you are a complete novice.


What’s the Ballistic Protection profile like? For example will it stop sustained .50 BMG fire from a crew-served weapon? Or is it designed to only stop sustained .30-06 fire from a shoulder-fired weapon? If the protection profile is there, then it would be the ideal barrier material for exterior walls in a residential structure, especially if said structure was located either semi or completely encased in a hill-side or underground. Of course that leads to the question about overhead protection against indirect fire weapons such as the universal 155mm howitzer round.

KC, wow man. Those are some important questions.  We certainly have felt at times like firing ammunition at the doomstead-in-progress. However, we haven’t actually gotten around to doing that. And since I don’t think I know anyone with access to a .50 or a howitzer, I’m not sure I’ll ever have an answer for you on those.  I do know that we used the 6 inch molds, so ammunition would have to get through 6 inches of concrete and rebar, plus the 2-5 feet of dirt and rocks used in the berms. Or it would have to go through a window.  :-D  We put windows in, since we like our sunshine and we like the pretty bit of land the doomstead is on.

Misc thoughts:   <– They have some great project pics.  <– There is an ICF magazine, for all your ICF reading needs. :-)

Spray foam is your friend!

Don’t forget to leave openings for your HVAC, electricity, telecommunications and plumbing. :-D

Thanks for all the questions! Hope these answers shed some light.

– Calamity Jane

17 comments… add one
  • Jarhead Survivor September 20, 2012, 9:22 am

    Way back a long time ago I spent time in an artillery unit shooting 155 mm rounds. Very nasty stuff. If I remember correctly – and I probably don’t or the technology has probably changed – a 155 mm round with a PD (point detonating) fuze set to delay (it’s like a 1/2 second delay or something like that) will go through about 18 inches of concrete if hit directly. And the howitzers we used to shoot (the M-198 or in the parlance of the time “the one-niner-eight”) were also capable of direct fire, so you wouldn’t necessarily have to have a round fall out of the sky in order to get a direct hit. Think of a big 40 foot gun shooting a five inch bullet packed with high explosive and a fuze designed to let it penetrate a little before it goes off.

    As to the .50 cal I know that the old M2 (lovingly called the “Ma Deuce” could shoot through just about anything with enough ammunition. Give me enough ammo and a few barrels and I’d shoot down a city block. And it’s fun too.

    Having said all that I highly doubt CJ’s redoubt will ever have to be put to this particular test, but if it something that worries you maybe this info will you give you something to plan for. Any of you military types with newer information please feel free to speak up here.

    I try not to get too “military” on here, but hey! You asked!

  • irishdutchuncle September 20, 2012, 11:08 am

    Thank you for the reply, Calamity Jane.

    I’ve seen some schemes where they use a large “balloon”, to form the ceiling. (I believe most of them just used a rebar cage. not sure I’ve seen it with ICFs)

    years ago they made concretete bridge decks using some type of slip form, or removable form. it’s very disconcerting to drive under one of those, and seeing sky, framed with rebar… (I got rid of my convertible)
    in recent times they’ve taken to using corrugated/pressed steel panels to hold up the pour.

  • T.R. September 20, 2012, 12:49 pm

    I always thought a subterranean would be good , this could be the ticket .

  • Ray September 20, 2012, 3:01 pm

    Hi guys, A 155 round dose not need to penitrate a wall. In 1944 the US Army atacted the sigfried line. The bunkers were made of steel reinforced fero-creat 3-6 FEET thick. Our GIs would drive a 155 howetzer to within 800 or 1000 yards of the bunker, fire ONE round and kill everone in it.The blast/concushon was egnough to turn the men inside to pulp.A .50BMG AP round will punch through a 6 inch concreat wall with no effort, and do it from 500 yards away.P.S. your dirt berm is a better bullet stop than the wall is. BUT; if you wish to stop a .50BMG you shold have at least six feet of dirt. The best you will get out of it now is to stop a 30.06 AP@ 200 yards. If you take more than 8-10 hits in the same place on your house wall the 30.06 is gonna cut a hole. The .50 will make a hole you can walk /crawl through. The 155 is a SIX inch naval gun, they kill everything. To stop a 155 ,you need four foot thick walls ,burried six to twelve FEET deep( a standard ww1 “bomb proof”)

  • Matt September 20, 2012, 7:41 pm

    Very satisifed owner here. Two story, lower story 1/2 underground, lower level ceiling/upper level floor is 3″ of concrete. I’d never want to live in a stick built house again.

    Would have to be pretty thick to stop a .50 with AP ammo (, but they are SUV proof (

  • irishdutchuncle September 21, 2012, 9:07 am

    regarding all the “foam” used in this type of construction, what are the concerns regarding: “outgassing” or fire? do the materials involved extinguish themselves after being exposed to a flame? how long after you build it do you still have the “new car” smell?

    I would definitely want US made, 5/8″ drywall, between my loved ones, and the foam.

    • irishdutchuncle September 25, 2012, 6:58 am answered most of my questions.

  • Keith September 25, 2012, 12:25 am

    I do heat and air for a living, several years ago a friend built a house of this design. Ihe requirements to keep his house cool are less than with normal construction. His ulities are extremely low. Also note in Texas they had some problems with ehe electric wire in the foam walls, might want to do some reasearch.

    • irishdutchuncle September 25, 2012, 6:34 am

      poor planning.

      electrical wiring should have been in conduit. conduit should have been in the concrete…

  • onesojourner September 26, 2012, 4:17 pm

    Actually wiring should not be in the concrete. Wiring should be in the foam. You use and electric chainsaw or a circular saw with 2 blades to cut a groove in the foam. the wire is pressed into the foam.

    • irishdutchuncle September 26, 2012, 8:25 pm

      yeh, I saw it in the quadlock video. I’m still not completely convinced. in the foam is better from a thermal and a structural point of view, I agree. I’d still go with conduit, or wiremold, under the foam. YMMV.

  • John Brown September 29, 2012, 12:31 am

    Depending on where you live, might dictate how and where you can do the conduit and wiring. In PA with hardly any fire codes, compared to MA, you might be able to bury inside the walls. In a place such as MA (1/3 the population of PA yet with a bigger government) with a heavy union history, you pretty much have to have every single thing inspected, and not hidden behind any wall as that is a no go on residential non-union work.

    A MA example would be poor Shaw’s supermarket when they made the mistake thinking they could use non-union labor to put up simple electrical conduit on interior block walls during new construction. I left MA before that fiasco was solved. Though I did come across an interesting link while searching for an example of the code/hassle.

    • irishdutchuncle September 30, 2012, 8:00 pm

      Philly is a Union town also.

  • Roger November 4, 2017, 11:20 pm

    Since a sphere is the strongest structure in nature, as well as the most usable space, do they make ICFs to build them? I would think this would give you the strongest roof available or perhaps a ‘indoor’ greenhouse for a ceiling/roof! Even a double dome with the top being made of plastic (greenhouse) panels and the lower dome made of ICFs for strength! As far as being bullet proof, nothing actually is, so don’t worry too much about it; in other words, if a modern army comes knocking at your door, you may as well let them in. On the other hand, I don’t think there’s any reason why you couldn’t use double ICF walls with a layer of sand/gravel in between. This should be very effective at stopping even .50 BMG rounds and absorbing the shock wave from explosives. I think placing a sphere-shaped ‘house/bunker’ about half way underground would be the best because if it’s completely underground, all an intruder has to do is block your ventilation tubes/pipes to force you out. Even if your bunker is very well hidden, the air being pushed out (especially at night) is going to be much warmer and will stick out like a sore thumb to a night-vision device! Unless you have a lot of internal space (or large compressed-air tanks) so that you don’t have to circulate your bunker’s air at night, then even a fool with a shovel could ruin your security plan! Also, if your structure is only half buried, then you can be more pro-active with intruders, also called shooting back! Small windows (about 6″ X 6″ with cross bars) that are slanted thru your walls will allow you to observe and if need be shoot back (or first) with built-in bullet traps to stop in-coming rounds. GLAHP! (Bunker-mania rules!)


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