Insulated Concrete Forms

Wow, what a Monday. QE3. 3 people! I rarely bother see movies when they get to 3’s. I always figure they’ve worn what ever premise started the enterprise a little thin by the time they get past 2. I’ll be the first to admit economics was not a subject I took many classes in. If there’s a reasonable argument for it, I’ll listen.  But, 3?! Color me skeptical.

“Insanity is doing the same thing over and over again but expecting different results.”

So, let’s do something different today. Let’s talk some hands on, practical nuts and bolts.  Or as the title suggests, Insulated Concrete Forms.

Insulating Concrete Form (ICF) is a system of formwork for concrete that stays in place as permanent building insulation for energy-efficient, cast-in-place, reinforced concrete walls, floors, and roofs. The forms are interlocking modular units that are dry-stacked (without mortar) and filled with concrete. The forms lock together somewhat like Lego bricks and serve to create a form for the structural walls or floors of a building. ICF construction is becoming increasingly commonplace for both low rise commercial and residential construction as more stringent energy efficiency and natural disaster resistant building codes are adopted.     Thank you wiki.

This is how the doom-stead was built.

There are many different materials and routes you can go with doomsteads. Along a continuum from cheap to expensive and easy to hard. Your doomstead should be built to survive in your microclimate, not mine. That said, hopefully this is useful to someone.

Some of the reasons why we chose ICF:

  • It was accepted in the county’s building codes. If you’ve never fought to get building codes changed, you’re in for an eye opening experience.
  • Quick construction.  When paperwork bogs you down until fall, it’s nice to know you still have enough time to get your doomstead enclosed before the winter snow halts everything.
  • Capable of holding up berms and a green roof. We knew we wanted those features, as cheap temperature and tornado protection.  (Bonus radiation protection too!)
  • Low upkeep costs. With the whole structure made of concrete, there is no wood to rot, or serve as home to bugs.
  • It’s cheap to heat. Yay for buried concrete, cold Iowa winters are made bearable with minimum cost.

Other methods we looked at included adobe – from what we read, adobe doesn’t do so great with the amount of rain that we get here in Iowa. Rammed earth, had the problem with moisture and temperature range, with the added bonus of not being approved for residential dwellings in our county. Strawbale – also has problems with moisture, as it’s usually covered in adobe. Stick frame is cheap and traditional, it but would blow away with the first tornado. We’d have to dig a cellar to make it safe, and why build two separate ways, for one building, that’s just added complexity.

The basics:

  • Plan your structure. Think modular and rectangular.
  • Dig your hole. This part can be done DIY. Have fun with it!
  • Lay foundation tile, footings, per your local standards.
  • Pour foundation.
  • Hire a crew to put together your insulation forms. This is amazingly low tech. The local crew in our area is 3 guys with big ladders, and they snap the forms together with little plastic pieces; like adult sized Legos.
  • Pour walls.
  • Build brace for the ceiling pour. This part can be tricky, we had to do our own engineering because there wasn’t a local engineer who had ever done anything like this and wanted to open themselves  up to the liability. We ended up with a bracing of 2×4’s every three feet, or something ridiculous like that. Totally overbuilt, but we knew if the roof pour cracked or warped, we were screwed. So, we erred on the side of overbuilt.  And the roof pour went great. :-D
  • finish the exterior. Berm or brick, whatever.


It worked well for us. Any other ICF’ers out there? Sound off with comments or questions.

– Calamity Jane

13 comments… add one
  • riverrider September 18, 2012, 10:11 am

    we used pre-cast concrete walls. they are great. they build them in a factory and truck them to site, set them with a crane. no foundation neccessary, just level a spot and put down 8 inches of pea size gravel. the walls have insulation built in, are very hard and waterproof right from the factory, with metal studs imbedded and holes for wiring/plumbing built in. took 2 days to excavate, 2 hours to set the walls. done! oh, and 10foot tall. a finished basement is still 8 foot ceilings. my next home will be just these and a concrete or metal roof.

  • irishdutchuncle September 18, 2012, 10:40 am

    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? does the ceiling structure get “keyed” to the wall in any way, or is it all held together with rebar?

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

  • Don Bowen September 18, 2012, 11:16 am

    We are contemplating building a house here in the ozarks. One house we looked at used ICF for the walls and trusses and tin for the roof. It is very tight, they have to open a window to use the wood stove. Cost was about 6% over stick frame.

    A stick framed house we toured used 2X6 on 24″ centers. It is a very tight house with a heating bill about half ours for the same size.

    We are going to tour another house made with SIP (Structure Insulated Panels). We do not know the cost of using SIP. They used ICF for the walkout basement. They had to import people to do the SIP.

    I am researching smart framing but the builders here do not want to try something different. This is tornado country, there are no building codes or permit requirements, and I will be heavily involved in the construction doing what I can myself. As I mentioned builders here are reluctant to try new things.

  • Don Bowen September 18, 2012, 11:49 am

    We are considering build a house and are researching various options. We are in the Missouri Ozarks, an area that has tornado. This county also has no building codes or permit requirements. Builders hare can be afraid to try new things.

    We toured a house built with ICF. The house if very tight and they have to open a window to use the wood stove. The cost was about 6% above conventional.

    Another house we toured was a stick frame with 2X6 on 16″ centers and blown in insulation on the walls and bats in the attic. It was about the size we are considering and his energy bill is about 1/3 ours.

    We will be touring a house built with SIP (Structural Insulated Panels). I do not know the cost benefit of that yet.

    I have researched “Smart Framing” using spray foam insulation. It looks to be a small cost penalty but a huge energy savings.

  • child of Odin September 18, 2012, 11:51 am

    As always, this is my favorite blog. A couple questions, and comments. 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. Sencond question: how does this compare, price wise, with conventional building methods? Third: you use a crew, but how DIY friendly is it.

    OK” comments. Although I am interested in this type of construction, I would like to build an all stone home. I pive in the Rockies, so stone isn’t lacking, and have been a stone mason for 15 years, but that whole zoning thing… I’ve also looked at dirt as a possible material, and although moisture can be a problem, and maintenance is an issue, I’ve seen cob houses in England that are 500 years old, rammed earth homes in the middle east that are 200+ years old, and adobe all over the west. In places like England, you need a large roof overhang and a foundation (stone or concrete) that sits high enough that water won’t splash up on the dirt portion. Still zoning issues here though, but thought others might be interested in knowing its drawbacks can be dealt with. ;-) thanks for this blog

  • Don Bowen September 18, 2012, 11:51 am

    Sorry about the double posting, I received a screen full of errors the first time and when I checked did not see the comment so did another.

    Delete either one if you want.

  • Yoda September 18, 2012, 2:01 pm

    Spot-on SHTF

    You have earned your proper place for practicle preparation on the WWW. Well done
    1Be aware and prepare!
    Respectfullly, Yoda
    “Terrorist Attack On America:

  • Ray September 18, 2012, 2:43 pm

    WOW! far out! I’v never seen them in KY.. THANKS .

  • Russ September 18, 2012, 6:57 pm

    We used these to build our house in 2001 and they were great. Fairly easy to use and the energy savings were really good. We heated our house with gas for about $300 per year (3,200 sq. ft.)

  • KC September 18, 2012, 8:54 pm


    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. Thanks for the opportune post.

  • SLHaynes September 18, 2012, 10:45 pm

    This type of construction may work well in climates with reasonable humidity. As Calamity Jane stated it might not work in your microclimate. Here on the Gulf Coast, humidity is a huge issue when considering your construction technology. The foam insulation would be like living in a refrigerator and without a great A/C system or a loss of grid power to remove the humidity, your house would soon become a black mold garden and uninhabitable. Otherwise, a well ventilated form of this home, without depending on grid powered A/C, may work.

  • John Brown September 28, 2012, 11:51 pm

    When I worked for Habitat For Humanity, about 12 years ago, they were just starting to use ICF on a regular basis. For us, it was because once the pour was done, a month later we could put up the walls and have all the anchors in place for stick construction and it solved cost and construction problems for stuff below grade. It makes hanging interior panelling go faster too.

    In the NE/Taxachusetts many houses are built with a cellar, furnace, and 200+ gallon oil tank. No one does slabs (frost heave) and in many places it was not worth the hassles and cost to try add gas to a house that did not have it, especially if it was uncommon or did not exist in the neighbourhood.

    One nice thing is ICF walls repel water better then cinder blocks and stand up to the hydraulic pressure better without bowing.

    For SHTF construction, 10,000 psi concrete, lots of rebar AND mesh, combined with 6″ walls makes it nice and cosy. Personally, I like having the poured floors supported by girders/8″ I beams, which are supported by and lagged to interior ICF walls. You can use the empty space of the I-beam to run HVAC and most of your electrical and plumbing if you wish.

    The above walls by theory will stop a 30-06, especially with an aggregate mixed in to stop splinting/spalling on the interior.

    When using ICF the only thing I don’t like is when people take a chop saw to cut out windows and doors. You should really do a pour with your steel casements in place and properly lagged. If I was doing my own house it would be with real grade 8 threaded rod and not cheap zinc stuff from China.

    This system here provides for a nice floor/roofing system and they have been in business for a while doing it.

    One of the most popular DIY forms.

    These people make a nice roof/floor system (never used it myself though or seen it poured):

  • John Brown September 28, 2012, 11:55 pm

    FWIW: This has always interested me for remote locations. Naturally, not too bullet or fire proof, but, still, I like it.


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