February 2nd
Posted on February 2, 2014 by
Virtual Build
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.
Sourcing
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.
Shotcrete meet
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.
pic from monolithic.org
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.
