In this segment, we mark and place the front columns and the curved I-beams that form the framework for the entry and green house sections. Most of the time-lapse footage was lost some how, but I did have some pics…
I bought the columns from the surplus steel place in my area. The cost was low enough that I didn’t mind a few imperfections. No regrets and I will probably do it again. I did put tape over the holes to keep wasps from moving in.
Trouble with the Forks
When I bought the skid steer, the guy who sold it to me said he also had a beat up set of old forks that I could have for 200$. New forks cost 3 or 4 times as much, so I told him to send those with the skid steer even though I hadn’t actually seen them. At first, I just noticed that the back board was a bit damaged. After using them, I also noticed that the two forks were actually different thickness (miss-matched set) and had bent slightly differently and I was having trouble holding things level.
We didn’t worry about the back board, but my father and I fixed the “uneven” issue with some torches (and lots of patience) to heat up one of the forks so we could bend it to match the other.
But all that time, I was using the forks to lift heavy things, so I didn’t notice the 3rd issue… When you apply loads the other way (pushing down on the forks), the locking mechanism is supposed to hold them in place. However, the top ledge that holds the locking mechanism in place had been slightly stretched upward and increased the tolerance by maybe 1/4th of an inch, and that was enough for the mechanism to actually detach when the load was pushed the other way.
While setting the second I-beam, The beam got hooked on the bent back shield and wouldn’t let me lower the forks. Since this flipped the load direction, it also shifted the locking mechanism down 1/4th inch relative to the forks and they detached from that top edge.
With the load direction reversed, the forks detached from the skidsteer
Those Forks are a few hundred pounds of heavy steel, so rather than just let them fall off and possibly damage something on the way down, we strapped them to the quick attach mechanism on the skid steer so we could still lower them carefully.
The final fix was to weld 2 pieces of angle iron across the top of the quick attach mechanism to remove the gap so it won’t be unlocked by a reverse load.
Final view. There will be windows under most of those Ibeams and a Front door under the left most one. Earth covered in grass, etc. will be above.
These concrete ribs were designed to give me more of an open space feeling without needing to build a wide and tall vault. For more about the design of the ribs or how I made the forms, you can read this earlier post.
This was really an epic part of the earth sheltered home build project, spanning (no pun intended) much more time than I would have liked. The costs for the forms and concrete were pretty minimal, the majority of the cost was actually in hiring the crane to move them around and set them up.
Side note: since I am so far behind… I will probably go and improve the section on the timeline next. Thanks to those of you who wrote to inquire if I died. Nope, just really busy and didn’t have time to put a video together. Speaking of which…
The Pump truck did not make things easier. Pump trucks are expensive and I needed it to come out for the floors anyway, so the first few rib pours needed to be coordinated with other jobs. This complicated the planning and made the pour days harder. It also slowed down the progress on the ribs by delaying the pours. And after all that extra planning and delay and expense, it was just plain harder to fill the ribs from the pipe than from the chute because it was really difficult to move it around. I guess my advice here would be to talk to the concrete guys and ask them how they would recommend you handle it. It was probably obvious to everyone except me.
Originally, I used silicone caulk to seal the bottom edges of the forms against the floor. However, this was a pain to clean up later. For the 2nd set, we used play-dough that my wife got cheap on clearance somewhere. The play-dough came up easily enough at the end, but it was such a pain to roll out and put into place that we ended up going back to the silicone for the later ribs.
The first set of ribs took about 4 hours per side to polish. I would start with a diamond cup wheel and then follow up with successive polishing pads at 50, 100, and 200 grit. I also used a special wheel to put a 3/4 inch round on the edges. For the second half of the ribs, I got a larger, more aggressive diamond cup wheel. It worked so well for the first step, that I quickly did all the other ribs. It was only when I got to the 50 grit pads that I noticed the diamond cup wheel had made deeper scratches than the previous one and it was much more difficult to remove them. I even went back to try the less aggressive cup wheel once I realize that the 50 grit was not working well. Overall, this mistake cost me several extra hours for each rib.
The moving dollies were supposed to be able to handle 1000lbs each, but that was clearly an exaggeration. I used more than 10 for each 5000 lb rib and still we had crunching sounds as their ball bearings exploded out all over the floor. The tires on some of them shredded completely. Eventually, I learned that most of the damage happened as each wheel rotated into the correct position to roll forward. By the time I got to the 3rd set, I had learned to point the wheels all in the right direction before lowering the rib on to them. This increased the survival rate considerably. I also salvaged partially damaged dollies by consolidating the less damaged castor wheels on to other dollies.
The rubber form liner molds were an interesting part of the build for me and I like the final look on the ribs, but again, not the best idea. More details below.
Liquid Rubber Form Liners
Originally, I planned to use the Styrofoam ceiling tiles directly, but after handling them a bit, I was worried that they were too fragile and wouldn’t last thru multiple uses. I also thought it would be a bit tricky to place them in the form so they would be centered because they were a bit narrower than ideal. However, if I used the ceiling tiles to form durable rubber form liners, I could get longer pieces that would be reusable and would be the inverse of the tiles. I could carefully center them on a board of the right width so the full depth forms could be easily placed, etc. I did some math to find the volume that I would need and found that I could get the PolyTek 75-75 ingredients for about 175$. That seemed reasonable enough to me at the time. The box of foam tiles was about $40. However, I soon discovered that mixing carefully was critical. My first few attempts were mostly good, but 95% isn’t good enough to cast concrete with. I only ended up with enough decent panels to do a small section of the first few ribs.
For the living room ribs, I decided to make the panels a little thicker (these were the ones I showed in the video). I would need to order more liquid rubber. This time, it was more like 225$, so I was in for roughly $400 worth of liquid rubber. That would have been enough to buy new Styrofoam tiles each time, so not the smartest move in hind sight.
I didn’t quite use up all my liquid rubber ingredients on the panels because I decided to try the Styrofoam ceiling tiles directly on each alternate rib. This way the pattern inverts, positive/negative for each rib.
Cost and timing
See the other page about costs for the forms, but they were just a few hundred dollars and were reused for all the ribs. So divided by 11 ribs, that is just about 30$ each.
The rebar was fairly affordable also. We used about 60$ worth of #5 and about 50$ worth of stirrups, so about 110$ per rib. There were also some steel plates that I built into the ribs and I think I paid about 10$ each for those from the scrap yard. Tie wire and welding costs are hard to guesstimate, but lets say it is less than 5$ per rib.
The concrete was about 1.3 yards per rib, which would be less than $185, even after some waste (Concrete costs about $100 per yard, delivered, but there are a couple other charges).
The molds and ceiling tiles were about 450$ total, so about 40$ each.
Then I bought about 20 of those little moving dollies and some other miscellaneous stuff for about 220$ total, so 20$/rib to move them out of the garage.
The grinder and all the pads were under 220$, but I still have the grinder many of the pads, so I am just going to leave that stuff out.
So lets say the total was $400 per rib. Not bad considering the quote to have it done by someone else was about $8,000 each.
Unfortunately, the crane and welding the ribs to the ring just about doubled that cost. The guys from RTC were great to work with and I appreciated their help, but I had not budgeted enough in that area.
Timing varied as I got better at each task, but here is the rough break down in man hours.
Form prep took about 2 hours per rib and includes cleaning the form segments, fixing any damage, re-assembling the form and attaching it to the floor, and then caulking the bottom edge.
Rebar was next and was taking about 8 hours on average, including getting all the rebar in, tying and welding.
After the rebar was in, I needed to call for an inspection, which didn’t take much time, but did delay the next step.
Next was the pour. It actually took less than half an hour to pour each pair of ribs, but then we would spend at least an hour or so troweling and finishing it off. Lets be generous and say 2 hours per rib. Then there was some delay (several days to a week) as we let the concrete cure.
Then we would spend about 6 hours (3 hours each) unpacking and moving the ribs out of the way. This included a lot of clean up.
And then the cycle could repeat.
After the ribs were out of the garage, I could polish them. The first half took about 4 hours per side to polish, so 8 hours per rib. But, thanks to an overly aggressive cup wheel and adverse weather conditions (hose freezing, etc), the second set took about twice that long. Lets put in an average of 12 hours per rib.
The flip and setup time wasn’t too bad, but lets write it down as an hour each there.
This brings the total hours per rib to about 28. I had 11 ribs to make, so about 308 hours total. If I had done those in 40 hour work weeks, it would have been nearly 8 weeks of constant work (yes, some of those hours or days were worked by other people like Sherri, Bonnie, Aaron, Dan, John and Mark). However, I already had a full time job, and also had other things to work on at the house, so I ended up spreading this part of the build over a whole year. The video on this article covers from July 2015 thru April 2016.
Needless to say, I am glad the ribs are all done.
After a long and difficult project, looking over the pics feels pretty good.
To illustrate how you get tangential arcs, important here because the load paths are smooth and in compression
3D model showing the ribs and curved steel I beams.
Model showing the kitchen, I included it here so you could see where the kitchen door slides into the rib.
Euclidean geometry can be built with nothing but a string and nails…
At the corners, it is best to overlap the rebar like this so that neither side can be pulled thru
Ryan and Carter helping with the hose
Moving those 5000lb ribs tended to wreck a portion of the wheels on each cart. Rather than toss out the whole carts, I would consolidate the good wheels together so some of the carts could be used again.
First rib lifted up… I tiled the image so the rib would look upright
At one end, the rebar is welded to a steel plate and this still plate gets welded to the steel compression ring when we set it up.
On cold days like this, I placed a heater in the middle and also covered with rigid insulation before leaving for the night.
Love this pic of Michael playing on Ribs 7 and 8 while we are finishing up prep for 9 and 10.
Work often runs me past sunset, especially in the winter.
Ribs 7 and 8, ready to pour.
We used a wet grinder to polish the concrete. It had various different cups and polishing pads.
Rebar was fun, the first time, but got old fast. In these joint areas, it got a little messy
#5 rebar along the spine with #3 rebar stirrups to tie it all together.
Some times I welded in extra bars just to keep everything oriented and spaced correctly.
Ribs, forms removed and ready to lift.
The boys playing with balancing against concrete paving stones we made
Polishing the ribs as a snow storm rolled in
Another snowy day… It was above freezing, so I still polished, I just had to get the ice out of the hose first.
Sherri and I were pretty happy after curving the last of the #5 rebar… Just a few more hours of rebar tying left on the last rib.
Sherri’s father (Mark) came out to help pour the last rib.
By this 11th rib, Sherri and I pretty much know what we are doing.
Sherri pulling down the last bits of concrete from the chute
Finishing up the last rib and knowing I wouldn’t need to reset it felt pretty good.
This bottom end of the rib was broken off when the strap slipped and it was dropped. You can see the yellow target that I pained to help guide the crane in. There was also a #5 rebar peg grouted in the middle of the square.
The crane company said I should label this pic as “Mike, the RTC oompa loompa”. All good guys to work with.
We used these bolts to attach the steel brackets to the ribs
The steel attached to the concrete
The view from below after the ribs were setup. This is our “open concept” living room…
Over the past couple weeks, I put in half an hour here and there in the evenings and moved the virtual build slowly along. Of course, I would be thrilled to get this virtual build speed in the real world ;^) Initially, the plan was just to illustrate the building process for various subs that would be helping. I planned to just show the construction of the basement, central tower and how the ribs would be setup. However, as you may have seen over the past couple posts, the virtual build has already helped find and solve so many problems that I have decided to press on with it. I added the garage and I am currently working on the bedroom wing. Next, I will work on the front of the house.
Virtual build as of Feb2nd, the garage, mezz and other areas are mostly complete, I am working on the bedroom wing and will work on the front of the house later. You can already see that this house design is very original.
I had been thinking a lot about how to lay out the ribs while I was casting them, I thought it might be a good idea to illustrate that with the virtual build. For a long time, our plan has been to pour the garage slab early in the build, but only setup the rear of the quonset hut. I could use the partial construction as a covered workshop in the back while I setup the rib forms on the front half of the slab. Without the roof in the way, I could use a crate to lift the 4500lb concrete ribs up and over to where they would be set.
I had planned to make a left and a right rib form because it would save me needing to flip and polish the “back” side of one that would be exposed against an end wall. I had already worked out (mathematically) that I could fit two of these on the slab in front of the partial quonset.
Now I was working on my gantt chart and considering how much time would be taken making these only two at a time. I also considered how much extra cost would be incurred with the multiple crane visits (to set them up 2 at a time). We had already planned to put a slab in-front of the garage (even if the rest of the driveway will be gravel), so the boys could play basketball. I started considering the option of placing the slab earlier in the process and building a few more forms. Even if the extra forms cost an additional 600$ each, I could make 2 more and save on 2 expensive crane visits and a couple weeks of time. I would probably at least break even on money, but save time.
There would be no additional cost to adding the concrete pad early since it was already planned for later in the process, but it may later be seen as “in the way” as construction equipment would need to be careful not to crack it…
So, I added the ribs to my garage model… You can see that it would be very difficult to fit a 3rd rib on the pad. Yes I tried other configurations, but I need room for the forms around the ribs and space too work, and I couldn’t let them go under the quonset or the crane wouldn’t be able to lift them up without dragging them. However, for the other ribs, I decided to make two left hand ribs and they can be put closer together…
Then it occurred to me that I needed to go back and reconsider my earlier decision about wanting to start with a left and a right rib to save time/money polishing (because one side would be placed against a wall.) I decided that I would save more money and hassle with the more compact arrangement of same-side ribs. In the software, it is pretty trivial to make the necessary changes and voila! Four ribs in a compact arrangement on the one slab.
I will update the Gantt to show building two forms first, then working on the second two forms while the first two ribs cure… Then I could position all 10 ribs in only 3 crane visits instead of 5. Of course, I still need to polish the back sides of the ribs, so I will need to flip them over before I set them, but I can place them in the (soft) dirt for that and I think I can get that done with only one extra crane visit for the full set. It seems like a plan for now.
Other revelations included that the steel stud layout for the bedroom was messed up by the architect (yup, I checked my original notes). It was a classic symptom of 2D design where the various views, created separately, were not actually compatible or build-able. I went back to check my original notes and sketches that I had sent in and they were correct, so I guess the architect just didn’t understand. I will document that another time. Lets just say my errata list is growing.
I have started hearing back from various contractors and the bids are looking much better. I got a very reasonable excavation bid to go with my good footings bid. I got bids on hooking up my electricity (a very reasonable $285 to setup the temp construction meter and then about $4.60/ft to run the permanent cable and setup for 400 amp service. I am waiting on an electrical and HVAC update that should be in early next week. It is clear that I still need to find a reasonable plumber bid (the 6 I got last year were all either too high or too un-reliable).
I also got prices on HDPE pipe for various diameters… Trying to understand the pricing structure better, I divided the price by area, weight, etc. and quite reasonably, it turns out to be priced by weight. $1.25/lb, delivered. For 8 inch pipe with a 1/4 inch wall (HDPE 8″ DR 32.5), that comes to about $3.83/ft. I need about 450ft for an earth tube loop, plus about 350ft for internal duct work in the house… So that goes into the estimates.
A highlight of last week (for me anyway; I am not sure how your week went ;^) was a meet with my most-likely shotcrete guy. I have been talking to a couple other potential shotcrete contractors, but one is just not big enough scale and the other is not really sure about the whole earth sheltered concept. At this point, I trust Nate more than the others and I think his prices seem fair. The biggest problem is that he is hard to get ahold of. It has been more than a year since we managed a meeting. My project is just too unusual for him to quote confidently, so he had agreed to a time and materials quote, but I needed a better idea of how long he thought things would take and I still hadn’t got a quote on some aspects of the build, such as the specfinish on the inside.
I drove out to his place, which is about an hour from my current home and about 40 minutes from the building site (its a big triangle around Ann Arbor, MI). He had a couple big friendly dogs and a nice sized kitchen table to lay the plans out. I set up my computer and showed him my virtual build, my Gantt chart, etc. My main goals were to make sure that the plan for the build made sense to a professional and experienced shotcrete guy and to get good numbers for budgeting purposes. I showed him the virtual model and we talked about practical things like how to get the rebound (shotcrete that doesn’t stick to the wall and is, therefore landfill) out of the basement. We talked about the possibility that some of the non-load bearing walls could be built hollow (or filled with insulation) and still covered with a thin coat of shotcrete to match the more solid walls. We talked about hiring some of his guys to help tie the rebar (along with other tasks), and how quick they could work. He even shared some trade secrets about the fastest ways to tie rebar, plaster walls, etc.
Along the way thru the virtual model, we kept referring back to the Gantt chart, which included things like the dates for each of the 4 shotcrete phases and the amounts of shotcrete that needed to be applied in each phase. He factored in if it was high work or regular walls (which he kept referring to as “money walls”), etc. We discussed if the dates were good for him. He was a bit concerned about the first shotcrete date because it was in May, which is prime swimming pool season. The other dates are past swimming pool season, so he will be glad to keep his schedule busy.
We discussed equipment that I would need to rent and what his crew would bring (and the associated costs). No surprises there except that he mentioned he would bring lots of scaffolding at no additional cost, he just wanted me to make sure the floor was level enough to move them around.
We discussed how much notice I would need to give to schedule his crew.
The main rough patch came when I got to the part about using his gunite machine to spray the specfinish along the underside of the vaults. Nate did not want to do that. Apparently, it is messy horrible work. See this pic from monolithic.org where they create inflated fabric domes and then coat the insides with shotcrete to form the structure. Note the full body coverage including saran-wrap on the helmet. When the operators face gets covered, he can pull on the roll to get a clean section. My plan had most of the shotcrete structure applied from the outside and only a very thin (3/8″) layer applied on the inside, but still…
Nate said he would rather just have his guys apply the plaster by hand, but that sounds rough and slow to me. We talked about other alternatives including spaying on the ceiling with a drywall hopper gun or having an acoustic ceiling company come in and take care of it. I had already got a quote on acoustical ceilings, but my wife didn’t like the samples I brought back and didn’t want to consider it at the time.
Another option may be that I would use the same glue up styrofoam ceiling tiles that I planned to use to form (impress) the ribs. It may look good to have the same pattern in the vaults between the ribs, but I am a bit concerned about fitting the square pattern to the curved and radiating vault shapes and it wouldn’t work at all in the compound curved bedroom vaults.
I left the meeting with a few notes on minor changes that I needed to make to the Gantt and process and some homework to Google search a number of things that were discussed (such as a rebar tie belt with a reel). I also have the costs I will need to complete this portion of the budget.