Information about design and construction of earth sheltered homes and a journal of my own progress

Fox Blocks, Phase 1


Posted on June 13, 2015 by

As part of my build, I wanted to experiment with a variety of different construction methods, including ICFs.

ICFs are “Insulated Concrete Forms” that you can use to build a very well insulated wall.  They stack like lego and include strong high density plastic (HDPE) inner supports that hold the sides together while the concrete is being poured.  This inner web structure is also used to position and support the rebar and the portion embedded in the polystyrene acts as furring strips for attaching things to the wall. After the concrete is poured, the forms are just left “in place” as insulation.

In addition to the 4 inches of polystyrene insulation, we will be adding 6 inches of concrete that will give the wall mass to retain heat, “dynamic R value“.

The front and back of my garage (Quonset hut) are flat walls that needed to extend past the Quonset hut and perform double duty as a parapet retaining wall, all without any complicated construction or difficulty attaching insulation.  ICFs seemed like the perfect choice for this application.

The final setup

The final setup

Installing the Fox Blocks ICFs was pretty easy, as you can see in the video.  Lessons learned are included in this post.

The Video:

Fox Blocks;

I looked at many different ICF companies and carefully considered their various advantages.  Some fold flat for easy shipping, others have longer or taller blocks or come in separate pieces that can be assembled in a variety of different ways.  Cost of materials and installation were also a concern.  In the end, Fox Blocks was my first choice.  For more on why, see this earlier post.

The blocks cost about 20$ each and I was able to buy them directly and install them myself without any fancy tools or equipment (or skills).  A regular concrete block wall (CMUs) would have been cheaper, but would have been much more work and required much more skill.  I would also have needed to insulate it, so maybe not even that much cheaper.

The Story (lessons learned in orange boxes):

The Setup;

ScreenShot_DimensionsWe started out by measuring and marking all the locations for doors and windows right on the concrete pad/footing. From this, we could easily mark all the locations for the rebar.  We drilled half inch holes 3 inches into the concrete at each rebar location.

The Fox Blocks stack very easily.  We also use the “Fox Clips” to clip the blocks together horizontally and vertically.  After each layer, we added the horizontal rebar.  My engineer specified one piece of #4 alternating near the front or back of the wall each 16 inches.  The internal web of the Fox Blocks had notches to hold the rebar so that we didn’t even need to tie it in place.

The lego bits (that Bonnie insists are called “nubbins”) are every 2 inches and the blocks can be stacked upside down or back to front, but you definitely want to line up the internal webs so that it is easy to clip things together vertically.  It also makes it easier to attach things to the outside of the wall if the webs are all lined up.


In the first section of wall, we had a T section for 3 levels on the back.  So when Bonnie got to the 4th level, it was a bit tricky to trim a block for that transition and you can see her trying a few different things (stacking and unstacking and then trimming and re-stacking) to get all the internal webs to line up.

After the wall was mostly up, we started dropping in the vertical rebar (half inch) and then using a hammer to tap the ends of the rebar into the half inch diameter holes in the footing.  These 3 inch deep holes were enough to hold the rebar vertical within the wall, however, in many cases, I still wire-tied the vertical rebar to the top horizontal rebar just to keep it all where it was supposed to be. This vertical rebar strengthens the wall and also helps the later layers hold across the cold joint at the top of this section of the wall.

When initially constructed, the blocks are securely attached to each other, so you have a monolithic form.  The vertical rebar keeps it from moving very far in any direction, but it is still very loosely positioned and not plumb.  You can see it moving around a lot in the video.  The wall will need to be plumbed and aligned as a final step.

We screwed 2x4s into the sides of the bucks.  It is very important to screw them in where the plastic reinforcement is.  In those locations (which act like internal furring strips), the screws bite in nicely and hold well.  Anywhere else, and they will just pull right out of the polystyrene.  these strips are hidden under the polystyrene. Fortunately, the blocks are clearly marked with the words “Fox Blocks” along the furring lines.

Unfortuneatly, I was not clear enough when working with my friends/family and assumed they all understood how the plastic strip locations were marked.  When their screws would not bite in, I would say something helpful like, “You need to make sure you screw it into the FOX BLOCKS.” and I would point to the line that said “FOX BLOCKS” vertically on the side of the block.  I would even screw one in for them to show them how it worked. They would nod and smile, but were actually thinking, “Yea, I am screwing it into the Fox Blocks, what did you think I was doing?  But its not working for me!”


It also didn’t help that we were (at least initially) using screws that were not threaded far enough up the shaft.  It was fine for the 2x4s, but when used with the thinner boards, the threads passed all the way thru the plastic and spun without really tightening up.  This caused quite a bit of frustration for Zack who was in charge of putting up the thinner boards.


Once the 2x4s were in place, we positioned and plumbed the ends of the walls using bracing and stakes to fix them in place.  Then we stretched string between the ends so we could align the rest of the wall.  Section by section, we used a level to plumb the wall and the string to align it.  The bracing at each section was individually staked.

This turned out pretty well, but I didn’t factor in potential movement at the bottom of the wall.  I had not fixed all the degrees of freedom and had relied on friction and the weight of the wall to keep the base where it was.  Of course, an ICF wall is relatively light and the strong winds shifted it in the 2 days between setting it up and the concrete pour.  I ended up needing to make some last minute adjustments.  Next time, I would also do something to secure the location of the back of the wall along the bottom edge.


Holes for the windows are cut out of the Fox blocks.  We used “Fox Bucks” to frame around the windows.  Fox Bucks are similar to the Fox Blocks (Polystyrene molded around an internal webing of tough HDPE plastic), but without the “snap together” feature. Instead, they must be taped into place and then the seams are held together with externally applied boards screwed in on both sides (the block and the buck).  Again, it is critical that the screws be in the plastic within the Fox Bucks, but the plastic fills pretty much the full sides, so it is hard to miss.

fox-buck1 fox-buck2

Not everyone helping understood that the concrete would be exerting hundreds of lbs of lateral force to push the bucks out and that tape and a couple screws would not hold them. I understood, but my big mistake was not fully inspecting (I was too distracted) that the boards were screwed into both the bucks and the adjacent Fox Blocks every 8 inches or so.  This lead to some blow outs and additional work down the line.  More images of this sort of mistake in the gallery at the end of this post.


The Fox Bucks are also used at the top and bottoms of the windows.  When used as window sills, we had to cut holes to allow the concrete to be poured in.  We also sloped the sills (by trimming the front of the underlying blocks) so water would drain off.

The full height of the wall is 12 blocks tall, but we only setup the first 4 levels because we wanted to be sure that the concrete would consolidate all the way down in the forms.  If we were more experienced, we may have tackled a deeper pour and got more done at once.  But as it was, I was glad we kept this first one simple.  Stopping at 4 levels also meant that I could let the first part harden before I added concrete across the tops of the windows and garage door, which probably saved me a disaster.  The cold joint that will occur is bridged by the vertical rebar.


The final steps were to place 6 mil plastic to separate the coming concrete from the Quonset hut steel and to spray foam some gaps and along the bottom of the wall. It not only fills gaps to keep the concrete from leaking, but works as a very effective glue.

The ICF wall was inspected and approved.  Keep in mind that the inspector checks basic things like if you have Rebar in place, etc.  He does not check for every screw.  As the general contractor, that was supposed to be my job.

Permit (Medium)

The Pour;

On the day of the pour, we also planned to take care of the basement floor and the concrete ribs while we had a pump truck on site.  I was actually running on fewer than 4 hours sleep and still frantically finishing some final details on the rib forms when the concrete trucks were rolling up.    I should have been inspecting the forms.  Is that enough foreshadowing for you?

Since I had experienced concrete guys on site to take care of the floor, I also asked them to help with the ICF walls also.    To make sure that the concrete was properly consolidated in the walls (without air pockets, etc.) I had bought a 5 ft long concrete vibrator for $99.00, which I would recommend to anyone doing similar work.

As soon as the concrete started filling the forms, the end started popping open.  It was immediately obvious that one of my helpers (who shall remain nameless) had not really understood that concrete would be trying to push its way out of these forms and had not secured things nearly enough.  For instance, on the first end, he had only fastened the top and bottom of the board.  Hundreds of lbs of lateral force were pushing out the middle and we had to scramble to brace it.  The windows bucks held up well, but then one side of the garage gave out and a few hundred lbs of concrete spilled out while we frantically grabbed scrap wood to brace it.  Seeing that not nearly enough screws had been used, I ran ahead of the concrete hose and frantically added more to the other bucks.


We made sure that the forms were not filled all the way to the top and we roughed up the top surface of the concrete so that the next layer would grip well across the cold joint.

It all happened very quickly… So quickly that, for the time-lapse, I had to slow it down by 50% so I could fit two sentences into the scene.

Once the day was done, I had time to think about my mistake and plan to do it better next time. There will actually be several more phases and I will need to wait until all the rib forms are done before I can complete the garage and put another ICF wall on the front of it.


Here are some pics from the day with descriptions.  Thanks to all those who helped me out.



Radiant Basement Floor


Posted on May 30, 2015 by

Earth sheltered homes normally get very scaled down heating systems (some even skip them entirely).  Where I live, a heating system is required for occupancy, so rather than get an expensive furnace that I would hardly use, I decided to go with an inexpensive “on demand mini boiler” hot water radiant system.  I got quotes for install that were as high as $60,000, but figured I could do it for a small fraction of that, so I decided to pull my own mechanical permit and do this myself.  I read a couple books and planned it out.  Then I bought the manifolds and supplies from (less than 400$ for the basement).

We got it all installed and inspected (our first mechanical inspection) and then had Dysert Concrete handle the actual pour of the floor.



Installing the radiant floor was easy, but some of the recordings didn’t work out, so the final video is shorter than usual.  You can read the story below for the details that wouldn’t fit in the narration.

The Video:

The Story:

I started with working out the layout on the computer.  Building code requires that no circuit be longer than 300 ft, and most experts recommend that you balance the lengths of the radiant tubes, so you definitely want to plan it out ahead of time.

I tried a number of different plans that ran the tubes thru the hall to the various rooms, but it was just too inefficient and cumbersome to get things “zoned” well that way.  In the end, I decided to drill some 5/8ths inch holes thru the base of the mechanical room wall to simplify the layout.  With the right tools (DeWalt hammer drill and a long 5/8ths inch bit), that was pretty easy.

We had leveled out the pea stone after the “underground inspection”, but David helped me do some final leveling of the peastone and then Zack helped get the 6 mil plastic down.  This plastic is important for keeping water vapor from the ground out of your concrete floor and is required by building code.  It also helps keep the radon out, etc.

Six MIL?

A mil is not a millimeter.  Six MIL is six thousands of an inch or roughly 0.152mm.  Before most English speaking countries switched from the imperial measurement system to metric, they would have called it a “thou”, based on the Germanic route word for “thousandth”, but for some reason, America decided to go “romantic” language based with this one and called it a “MIL” instead (based on the word for “thousandth” in languages like French or Italian).  This is a similar etymology to how the rest of the world got the word “milli” for the Metric system, hence the similarity.

HuskyWe don’t use “MIL” much in the USA, except for quantifying thin film thickness.

Since it is difficult to imagine things in thousands of an inch;

  • 5 MIL = grocery store bag
  • 5 MILS = Garbage Bag
  • 3 MILS = Husky Contractor Bag
  • 17 MILS = Pond Liner
  • 35 MILS = Credit Card


JigSaw Puzzle

David tossed us some sheets of insulation and we got started on the jigsaw puzzle.  My rooms are unusually shaped and since they didn’t actually stock those shapes at Home Depot, we cheated by cutting pieces.  We started with measuring, but usually ended up trimming each piece iteratively until it fit.  We taped all the pieces together and shoved trimmings into any gaps along the wall.  Not too hard, but certainly more time consuming than a square room might have been.  This probably wasted about 15$ worth of insulation, so not too bad.

Radiant tube

I marked the radiant tube layout directly o n the insulation based on that balanced plan I had carefully worked out on my computer.  I used piece of scrap wood marked with the right size increments and a can of upside down surveyors paint.  In addition to basic tic marks to follow, I also painted in the end loops so the whole plan would be pretty easy to follow.

Radiant_Layout_DrilledStapling the Pex tubes down was easy and fun, Sherri and I took care of most of it, but the boys were very eager to try it themselves.  I imagine it would have been quite a lot more difficult (and much less fun) without that commercial grade tool we used.  The tool cost quite a bit (~200$) but is very well built and I will use it a lot… I also plan to sell it and recoup most of the money at the end of the project anyway.



Connecting the pex to the manifold was straightforward and easy.  There are some simple little brass connector bits and you just tighten a nut to hold it all together.


Pex Stapler saved us a lot of timeI got the Manifold, Pex pipe, the Pex stapler, staples and the pressure tester from “”.  I had looked at lots of other sites (including sites that put it all together for you, such as, but this one had the best prices and the best hardware.  There are also easy to find “coupon codes”.

John (my brother-in-law) and Zack helped me finish off the third loop.

My sister Bonnie was in town and mostly helped me with the ICFs (another post/video), but she made it into this video by helping me to fill the tubes with water so they wouldn’t float in the concrete. I had been trying to pour it from the bucket into the funnel, but she had the idea to siphon it from the bucket, which was much easier and didn’t get us as wet.

Then we pressurized the system (according to building code) so we would know if anyone punctured the pipe before the concrete set.


Concrete day arrived and the guys started with putting down some six by six wire reinforcement.  This was left over from the garage floor and will help prevent cracks from growing.  It also helps protect the pipe and keep it all down under the concrete.

The concrete was pumped in from overhead (renting the pump truck cost ¼ of the job, but was well worth it in terms of making things go easier), and spread level.  They came back an hour later and hand troweled it smooth.



In all, I paid less than 1$/sft for the insulation, radiant tube, manifold and supplies, then 3$ for the concrete work plus an extra ~500$ for the pump truck and ~1100$ worth of concrete…  So, not bad.


I hope to get the “quad deck” in soon so we can put another concrete floor over this basement.


Cleaning out the slag


Posted on May 21, 2015 by

Now this was a tough long weekend.FamilyCleanup

Basically, the basement of our earth sheltered home was filled with approximately 11 cubic yards of concrete slag that needed to be broken up and removed so we could prep for pouring the basement floor.

It was something we have known we needed to do since last year, but were putting it off for obvious reasons.



Here is the video:

Why did this mess happen?

All this concrete was wasted shotcrete that wasn’t on the walls and should not have been on the floor either.

As you may recall, I had used steel studs to frame the basement and then placed metal lath on the inside to “catch” the shotcrete.  I had been told (by the shotcrete guys) that the lath would be enough to prevent much of the shotcrete (peastone) from blowing thru.  I was told to expect a thin layer of concrete on the inside, thin enough that it would break up into small fragments just by walking on it and that it would actually save me from needing to add as much pea stone later.

Watching the shotcrete being applied, it did appear that not much passed thru when it was applied at a downward angle onto the previous shotcrete.  They did do it this way for the first couple levels, and actually raised a scaffold jack platform twice as they went.  But then they got a bit tired and started shooting horizontally and even at an upward angle.  This allowed much more shotcrete to pass thru.

The effect was cumulative with blow thru coming from so many different angles, each adding its own layer of concrete.  The round central room was especially bad for this with at least 3 layers of 2 inch thick concrete across the floor.

And once the crew was working on the inner walls, there was also “rebound”, shotcrete that doesn’t stick to the wall, and “trimmings”, concrete that is cut off the wall because too much was applied in the first place.

All this concrete (that I paid for) ended up on the floor, but not in a good, “wow, you got bonus concrete floor along with your shotcrete” kind of way.  On average, I would say we had about 3 or 4 inches across most of the floor (in several layers), and up to 8 or more inches near the walls, especially in the corners.  It was uneven and lumpy and even had boot prints in it.  The whole feeling was somewhat “war torn” and more than a little depressing.

When I setup the main level, I plan to back the metal lath with fiberglass screen.  The metal lath will still provide the strength to catch the shotcrete, but the fiberglass screen will prevent any material from passing through.





Thought I would try to put some extra pics in here…

And the Story.

I like to include the text of the video, along with some extra info that doesn’t fit in a narration, so that the content is google searchable.

For this job, I had hired some teens, rented a jack hammer and taken the day off work to make the long weekend even longer.

The big question was, “How would I get this slag out of the basement?”  The final solution that I came up with was a Bagster dumpster that I got from Home Depot for 30$.


The plan was to load it up and use my trusty skid steer in to lift it up and out of the basement.

It took a bit of trial and error to figure out the best way to lift the bag and to empty it, but fortunately, we had lots of tries to get it right.  You can see how we did it in the video.

The bagster is supposed to be for only a single use, but it  held up very well, load after heavy load, for a number of days. The only tear was caused by dragging it up the rough wall in the first lift.

TeensThis first day, we were mostly focused on the edges where the thickest concrete was because I didn’t want to rent that 75 lb jack hammer for a second day.  The heavy jackhammer was actually very effective on the thick concrete, but kept getting stuck in the thinner stuff.  For that, the 11 lb breaker was much more effective.  My Dewalt hammer drill also got a work out.  At the start of the day, I couldn’t get the teens to touch the power tools, but by the end of the day, they were much more comfortable with me and the tools and were taking turns on the jack hammer.

On Saturday, my parents were in town, even though I warned them that we would be taking on the worst job of the build so far.  I also hired Zack again, he was one of the teens from the day before.

My father got to cutting a slot in the footings (doorway) for the radon tube while the rest of us got cracking on the concrete slag.  Our radon tube was made of a 4 inch corrugated drain pipe, wrapped in landscapers fabric to keep dirt out.  It just gives radon an easy way to escape so it won’t build up under the basement floor.

Then my father and I worked on the floor drains while the others just kept right on cracking up that concrete.  In order to get the slope correct from the floor drain in the central room all the way to the outer wall, we had to cut open the tops of the footings.



We had planned for holes in the footings to run these pipes, and I had even come prepared with 4″ PVC to use to form them.  However, the guys doing our footings told me they brought their own 4″ corrugated drain pipe, which they nailed in place very quickly.  The problem was that the flexible pipe “floated” up in the middle when the footings were poured. Instead of being a straight sloped hole thru the concrete, they bowed to the point that we couldn’t even get the 2″ pipes thru.  I guess they were not used to the footings being so wide.  Narrower footings probably wouldn’t have as much deformation due to “floating”.  You may recall this same issue cost me time and money during several other stages of the build. Hopefully this was the last of it.


Then we came back out again on the holiday Monday, just my wife and kids.  Sherri and I cracked things up with the 11 lb “breaker” and the boys scrambled to collect the pieces into the buckets.  When the buckets filled up, one of us would dump the bucket in the bagster.  The boys were motivated by being paid 1$ per 5 gallon bucket.  They worked for several hours before wearing out.

With the big chunks finally removed, we raked the smaller bits and then brought in some pea stone, which is required by code in my area.

I came back on another afternoon with Zack and my friend Aaron to get the second half of the pea stone down and rake it all level.  At one point in the video, you can see Aaron intentionally took a pea stone shower, just to see what it would feel like.  I don’t think he will do that again.

BuildingPermit_blurThe final product was a a peastone under-floor that meets building code.  The black pipes are to channel radon out of the home and the white pipes are plumbing or drains.  The inspector approved the work and we were able to rake the pea stone level and move on to the next step.

Next step is to get the vapor barrier, insulation and radiant floor tubes down here so we can pour the basement floor.


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