ICF blocks seemed like the perfect solution for the front of my garage where they would be needed as walls for the garage and as a parapet to hold back earth over the roof, without needing any special handling for insulation. There have already been previous posts about my Fox Blocks training and my early work with these. Now that I am all done with installing my ICF blocks, this post includes FAQs about my lessons learned, costs, etc., but first, the video
Video
Earlier Post
There was an earlier post about why I chose Fox Blocks, the training, etc. The rest of this post will be about lessons learned since then.
FAQs
Why pour in a series of small pours?
The more concrete you pour at a time, the more pressure is exerted on the forms and the more concrete will come spilling out if anything goes wrong. In other words, I wanted to take baby steps.
I also couldn’t pour the front wall at the same time as the back wall because I needed to leave the front open while I continued to make those big concrete ribs in the garage.
I couldn’t wait on the back wall because I needed to mount the electrical service somewhere and the pump truck was cheaper than it would be to start on a temporary structure and then move the meter.
Even brave people are limited by the physics (hydrodynamics) of pouring concrete, so I did pour the front wall in only 2 stages instead of 3. But even with my growing experience and confidence, I didn’t sleep well the night before we did that pour over the garage door openings.
Why Scaffold Jacks on the north side, but regular scaffolding on the south side? Why not ladders?
When you are building the ICF walls, I guess you could use ladders. It would be a hassle to keep moving them around, but it would be possible. However, when it comes time to pour the wall, you need to be able to move swiftly along the top of the wall. You can not keep stopping the pump truck to climb down and move the ladder . You need some sort of working platform.
The north wall was poured in stages over a long period of time because I was waiting for times when I had the concrete pump truck coming for other reasons (such as the basement floor or the quad deck floor). During that time, I knew I would want my scaffolds for other tasks, such as setting up the steel framework. Home made scaffold jacks were the easy and affordable solution because I could just leave them in place and move them up as needed.
By the time I got to the north wall, I was just paying for the pump truck and doing my pours much closer together, and I wasn’t using the scaffolding for other tasks. I also didn’t think the jacks would have worked well across the open garage doors anyway, and the driveway was nice and flat for stand alone scaffolding… So I just used my regular scaffolding.
How much did it cost?
I bought the Fox blocks at Menards, so you can check their website for the prices, but they were just under 20$ per block (16 x 48 x 12 inches). The walls then got filled with concrete that cost about $100 per cubic yard (27 cubic feet). There were also some clips and a bunch of wood (I used a lot of scrap from earlier projects), rebar that I already had laying around, etc. I buy the rebar by the ton, and pay something like 35 cents per ft. If I do some fun math, and divide things out per square ft…
Fox Blocks = 3.75/sqft
Concrete (6 inches thick) = $1.85/sqft
Rebar = 0.35 cents.
—————
Total = $5.95/sqft,
Plus a few cents for clips, etc. That is not too bad for a 12 inch thick wall, but it is about double what it would cost to frame a 2×4 wall with 4 inches of insulation and house wrap. I didn’t have separate steps to attach vapor barrier, insulation, etc. because those are all built in, but clearly, I still spent a lot of time putting up patches, etc.
I don’t regret going with the ICFs because I think they are much better in this application as parapet (retaining wall) for the dirt on my roof. The concrete wall will be much stronger and much longer lasting without any risk of rot, etc. There is also the dynamic R value of the concrete in the wall that will keep my garage much more thermally comfortable. My wife likes that no insects or mice will get thru it, but in the mean time, some birds are trying to make nests in the exposed polystyrene.
What I left out of the above calculation, because it is a real kicker for me, is renting the pump truck each time. Filling a 14.5 ft tall wall without a pump truck isn’t really a practical option. For the first two sections, we scheduled the wall pours to align with the basement and quad deck floors, so no additional cost there. However, for the other two times, we just had to pay for them to come out for just a tiny section of wall… Each pump truck visit was about 700$, which is more than the cost of the concrete we pumped. Each pump truck also required me to order a couple extra cubic yards of concrete just to fill the hose (that all gets dumped out at the end). If we were doing a larger chunk of the house in one go (such as a whole house built of ICF blocks), we could have improved that ratio a lot.
How about time?
Yes, I did this work over about 6 months. Mostly that was to align pour days with other tasks that would need the pump truck. I was also working full time and basically only building on Saturdays and some weekday evenings. The actual time spent stacking blocks was not too bad. How would it compare with stick frame? Probably similar. Certainly it will last longer.
What was with all those edge patches?
There are no attachment points on the ends of the fox blocks. They attach to each other, end to end, with clips between the plastic webs. The styrofoam just buts up against the other blocks, so it has some compressive strength, but no tensile strength for holding screws. When you attach the end bucks, etc. you need to connect to the high density polyethylene furring strips built into the front and backs of the blocks. To do this, I screwed boards (like 2×6 boards or sheets of particle board with 2×4 blocks) to the front and back of the ICF blocks and then I could screw the end boards to the sides of these.
I am pretty sure all the vertical end walls and especially the ones for the top of the garage door opening were critical for containing the concrete. The patches, such as the one along the vertical seam shown in the video, were also critical.
On the top edge of the wall, I had cut a sloping shape. When we poured in the concrete, if it was too wet (high slump), it may have simply poured out the sides again. I knew there would be some pressure on these sides, even if it was not as great as the vertical sides, and I wanted to contain and shape that concrete. The concrete did push at the top/side forms for the first 3 pours, but for the last pour, the slump was so low that the concrete probably would have just sat there in the shape of that hill and let me trowel it smooth. In that last case, the boards were just in the way and made it difficult to get the concrete down inside where it needed to be.
Tips:
1) The best tool to cut the ICG blocks with was a battery powered jig saw with the longest blade you could buy.
2) Get a concrete vibrator. Harbor Freight has a cheap one. It makes a huge difference to the flow of the concrete, which means you can get lower slump concrete (which sets up stronger) and still have it nicely flow around all the rebar and ICF webs without any voids.
Before buying the vibrator, I had wondered if it would be worth the money. Professional grade vibrators cost hundreds more. As it was, I thought it was a great little investment that got me thru all my ribs and my walls and died 5 minutes before the end. I haven’t needed it since, so I haven’t tried to fix it yet. Maybe just a switch died?
3) Because the ICF blocks look like lego, any many of us “do it yourself” builders were lego maniacs, we some times assume that overlapping the blocks (running bond) is important. When something in the wall makes this difficult, we might want to waste lots of time or chop up expensive blocks trying to prevent a vertical seam. But it is totally unnecessary. Unlike bricks (masonry or lego), the little styrofoam nubs on the ICF blocks do not actually hold the wall together in the long run. The void gets filed with a monolithic concrete pour that ignores all those stacking details. Instead, just focus on making sure the surface of the wall is patched so the forms won’t split open along the vertical seam.
Gallery
Just some related pics.
Continuing over the Door Buck
The boys can’t resist the camera
An accidentally pic as we moved the go pro
Aaron out on pour day
Ryan checking out the camera
Aaron and Simon handling it
Sherri troweling off the wall
2×12 buck for the exhaust fan
On the North wall, before trimming it. This platform is 14 ft off the ground.
North wall after trimming. It was supposed to be filled along with that floor.
Pouring the wall with Ryan
By this point, I was pretty comfortable with the concrete hose.
Here Ryan is climbing up the ladder to help me by vibrating the concrete. He doesn’t like heights, so I appreciated his bravery.
Full bracing
After removing the scaffolding, bracing and patches.
Starting work on the round window buck
I stacked these blocks, numbered them, drew and cut my circle hole and then took the wall apart so I could put it up where it belongs.
Sherri messing around for the camera
After getting in the window buck… Felt pretty good.
Night shot, I appreciated the lights on the short January days. It looks like a scene from an underwater exploration movie.
The south wall, before trimming.
Picking up the camera at the end of the night, looking tired.
Inside the Fox blocks wall, there are black HDPE plastic brackets to hold the rebar, etc. The blocks are “clipped” together with wire clips.
Sherri and Michael posing on the last pour day.
After the pour.
After removing the scaffolding and most of the patches.
Its a short one this week, and the end is rather abrupt, but here it is anyway…
Why a Quonset hut?
My house design is an experiment with a variety of different arch forms. Since it is a self build, I kept most of my spans shorter than 15 ft. The exception is the garage. I wanted a 3 car garage for practical purposes and decided to use a Quonset hut to form the wider span.
The quonset hut could probably support a significant earth load, if it were carefully distributed, etc. But in my design, it is really just fancy formwork to hold up the rebar and shotcrete that will actually support the earth.
My build also required a workshop to build the other components, and the Quonset hut is something that could be erected quickly, early in the construction, and provide that place. I have used it to weld steel arches, store materials, and most importantly, to form my large concrete ribs.
Why build it in two stages?
The rib forms needed to be built on a large flat surface, out of the weather. But we would also need to use a crane to move them to where they needed to go. The ribs weigh 5000 lbs each, so I couldn’t roll them out across the gravel or dirt. Instead, I needed to keep them on the slab, but also needed open sky above them for the crane.
The solution was to build only 2/3rds of the Quonset hut on the slab floor. I could use that sheltered space at the back to form the ribs. I would then jack them up and pull them forward to the open 3rd where a crane could lift them up and over to where they needed to go.
When the crane came out, it did lift them straight up and over, but I noticed that it actually had a telescoping arm. I asked the operator and he said that he could lift them up and pull them out of the building if I finished it…
The ribs were taking me a long time to make and closing off the building would save me a lot of hassle, so that seemed like a good idea. It had been almost a year since the first 2/3rds were erected.
The final 3rd
My parents came down to visit and to pick up their camper. Anyway, it was windy and we didn’t want to try erecting Quonset sections with just the three of us. However, that is a good number for assembling the steel arches, so we spent most of the afternoon doing that.
The following week, I put out help requests on Facebook and at work. The first few days, I was worried that I wouldn’t have at least 4 people there at one single time. By the end of the week there were lots of people volunteering and I was buying a few extra half inch sockets and wrenches so there would be tools for everyone. One co-worker even volunteered his whole family of very capable teens.
The steel ribs went up very quickly. 7 in under two hours. We were actually done before the Pizza lunch I ordered arrived. No worries, we had other work to do (not captured on film).
Mistakes
Because these new steel arch sections were were bolted to the rest of the Quonset hut, which was already bolted and concreted to the slab, and because they were very heavy, I wasn’t too worried about the new section blowing away. With 13 people working in parallel to bolt the sections together, I didn’t want to interrupt that flow and make everyone stand around while I drilled and bolted the steel sections down. I figured I would come back and take care of the anchor bolts next time…
However, by the next time I went out there, I found that the wind had lifted the front third of the Quonset out of the groove. We ended up wasting several man hours and a lot of sweat getting it back into place.
I should have known better because this is a pretty typical fluid dynamics problem that I had to do several times at school.
Another “mistake” that I pretty much accepted was that my building was a little longer than it should have been and ended up hanging over the edge by a few inches. I ended up cutting that off so it wouldn’t get in the way of the end wall, but that is another story.
After the Quad Deck ICFs were installed, there was still a lot of work to do before we could pour concrete, and then still a bit of work after.
Before we could pour, we had to install the pex tube for the radiant floors, build a perimeter form to hold in the concrete, put in plumbing, electrical conduit and duct work, and generally clean up any mess from the previous steps.
While we had the pump truck there, I also wanted to pour a couple 7 ft tall columns, so we also prepped those. We also poured a section of ICF wall, but I will save that for another post…
After it was all over, we had to remove all the forms. We gave the concrete a couple weeks to cure (and gain strength) and then we removed the scaffolding and shoring.
Video
You can find the Video here:
Experienced workers and new technology
They workers are used to pouring concrete on stable ground, so they were quite nervous about pouring on the ICF forms. They started out walking very carefully and there was a lot of nervous laughter. I made sure to pass along the pour instructions I had received from the Quad Deck installers. After the grooves were filled, the guys appeared to forget what they were standing on and began stomping around as usual. We had no problems with the Quad Deck system. Everything held up and there was only a little bleed water in the basement.
The blow out
During the column pour, the weight/lateral pressure of the concrete blew out the forms. To be clear, these were my column forms, that I built, not the Quad deck forms. My heart sunk as concrete spilled into the basement.
Next thing I knew, the guys from Dysert concrete, who were working on finishing the slab, jumped into action and helped strap the form and re-level it. This was really going the extra mile because they were really only there to look after the floor. They also went another extra mile and helped me scoop some concrete out of the basement. When it was all over and guys were packing up, I tried to give them some cash for their extra efforts, but they wouldn’t take it. If you are in the SE Michigan area, I recommend these guys.
In contrast, the pump truck operator (not my usual guy who is very helpful, so I won’t blame the company), clearly did not want to be there. He was grouchy from the start, perhaps not a morning person? When the floor was finishing up and I told him the columns were next, he complained a lot because he thought he was only there for the floor. He threatened to charge me extra. At that point, we were not even half way thru the minimum 4 hour window that I had to pay for. Also, I had specified (in writing) the volume of concrete and listed the columns and the ICF wall when I booked the truck. I didn’t bother arguing all these details with the driver, but I simply ignored his threat and told him it needed to be done before he could pack up.
Amateur legal note: If a contractor tries to change the price part way thru a job without sufficient justification, you can safely ignore the threat. Legally, if it would be even more expensive to switch contractors at that point, the threat of a work stoppage amounts to extortion and puts you in financial duress to agree with their unjustified price increase. In this case, I didn’t verbally agree to the extra charge, but I did tell him to continue on, which could be considered implicit agreement. However, even if I had agreed verbally, or in writing, I would still be able to contest the extra charges in court later due to financial duress making the amended agreement invalid. In order to increase the cost mid project on a fixed bid, the contractor would need to prove that the scope of the work increased significantly beyond a reasonable expectation. For instance, my septic field guys found a 1940’s garbage dump almost as soon as they started digging. The health department got involved and ended up raising the cost of the installation by about 30%, which I agreed to and paid without an argument.
When the columns failed, he was even more annoyed at the extra delay and kept saying he had another job to get to. I reminded him that he had been there less than half the minimum time I was paying for. A moment later, he started dumping concrete on the sand, we suspect it was intentional so he could leave. Sherri got mad and yelled at him until he stopped. However, as a result of the waste (intentional or otherwise), we did not have enough concrete to finish the ICF blocks in the north wall, but that is another story.
This pic is just one the time-lapse caught as I was moving the camera. It shows Sherri trying to clear the dumped/wasted concrete off the footings. Definitely not princess work, but I never asked her to do it… I was running too much to even think about it, but she separated it into smaller piles that I could move after it hardened, so I am glad she did.
Friends
You can see that a few of my friends in this and other videos and in the gallery below. Some of them actually like this sort of work, others come out and help anyway. I appreciate them all.
Working with friends makes the work go faster and the day fly by. Some of them have also taught me some good tricks based on their respective experience, or mentioned tools that would make the job easier. I will definitely have to have a big party when this thing is all done.
Pex connections
In the video, you might have caught that the pressure test dial didn’t hold the pressure when I filled it. I ended up using some dish soap from the camper to find the leaks. I had one easily fixed leak in the manifold, but most of the trouble was with the Shark Bite connections. Basically, I had not left enough extra length to reach down to my manifold (oops), so I needed to connect some short bits to make the final stretch. The SharkBite connectors are individually expensive, but easy to use without any tools, and I only needed a handful. However, try as I might, I couldn’t stop some of them from leaking. I talked to the plumbers (who use Pex for everything) and they said they prefer the crimp connections. I figured I would eventually be putting in a bunch more radiant, so I decided to spend the money on the crimp tool and it easily sorted out my issues.
Fibonacci Spiral
I had long planned to insert 1 ft long glass rods thru the Quad deck to let light thru in both directions. When it came to the layout, I went with the points of a simple Fibonacci spiral, centered in the room and leading around to a spiral stair case around the corner. Later, I can etch or mosaic in the actual curve if I want to.
These are sorts of fun little extras that make building your own home fun.
To keep the glass rods from being pushed thru the floor by the workers stepping on them, I screwed boards up underneath to hold the bottoms in place. This is why the lights turn off just before the pour in the video.
Rented Scaffolding
The scaffolding that I rented has been stacked nicely and ready for pickup for more than 4 months with no responses to my monthly texts to the builder to come and pick ’em up. You will see it in the background of various other videos ;^) It was actually quite labor intensive to remove it from the basement, so I hope the builder appreciates that that free labor. I wonder if I could surprise him with storage fees? I had to move it again recently.
