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

Life After Shotcrete

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Posted on August 23, 2014 by

Since the shotcrete went up, I have been working on other things such as getting my drain tile in and getting the basement plumbing done. There is video and timelapse, but I have not been able to put it together yet. Maybe I will come back and add it here.

In the mean time…

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It has all been pretty hampered by the fact that the shotcrete left a lot more concrete on the floor than expected.  Instead of being a thin crust that breaks easily, it is 2 to 6 inches thick across the whole floor.  This was mostly due to shotcrete blowing thru the lath and on to the floor inside. The mechanical room has it the worst because it is a small room with shotcrete coming in from all sides.  I will need to rent or hire a jack hammer to sort it out properly.

This shot is after spending an hour with a power chisel.

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Tomorrow, we head out again to spray on the elastomeric waterproofing.  We bought a paint sprayer just for the occasion.

Shotcrete!

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Posted on August 18, 2014 by

I have been too busy lately to put together a post.  However, about a week ago, I did manage this video of final shotcrete prep:

Then we got the shotcrete in and I started on a detailed video with close ups, etc. but it was too long (10 minutes).  I didn’t want to cut all the good stuff out, so I quickly put together a second shorter version this evening (with the promise of releasing the more detailed version eventually).

As with every experience, I learned a lot and will write up more details later.  The main thing is that I should have spent less time worrying about how flat the lath lays and more time tying the lath to the rebar.  I missed tying a few sections and they pushed out like an overstuffed pillow (except with concrete, so less fun).  I also learned that there is a front and back to metal lath.  It catches shotcrete better if it is oriented correctly.  The shotcrete guys really liked the steel studs, but they had me remove the 2″ wide steel strap after the first “lift” of shotcrete was in place. The wider strap was getting in the way and creating a shotcrete “shadow).  I’ll put a structural page together on this subject eventually.

Here is a pic of the shotcrete going in.  The nozzle man in the back is shooting and the finishers have to follow fairly closely behind before the concrete hardens.  The smokey air is like aerosol concrete mist.

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This next one is how they handled a 135 degree corner…  Sharp on the outside, nice rounded (and over 1 ft thick) on the inside.

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As for the final look of the shotcrete, it is a bit lumpier than I expected.  The optimist in me would call it “organic”.  I expected it to look like a pool (pretty smooth). The shotcrete guys usually make pools and they said they it will, after it gets plastered. I think I will need to grind off some of the uglier lumps first.

Here is a cross section of my the shotcrete around mechanical room.  They had to interrupt the spray so we could still get in and out (no doors in a basement wall).  some of the thickness variation was sorted out in later lifts.

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The cost was also higher than expected. The basement was expected to be just over 40 yards of concrete in the walls.  I had originally been told 1 day with 4 guys. Instead, 8 guys worked for nearly 2 days… I expected 6″ thick and got mostly 8″ thick, so my concrete volume was higher. There was also much more waste thru the lath than expected.  The concrete price had also gone up (from 84$ to 91$ per yard.) Things were in motion, and the overall cost is still fairly low, so I just rode it out.

In the end, I bought 40 yards the first day and 18 yards the second day (but we dumped several yards each day and ended the job with lots of concrete still in the mixing truck).  I still paid less (including steel, rebar, etc.) than I would have for a poured basement with straight walls.  But, I guess the poured basement would be smooth finished, and I still have a lot of plastering to do.  My shotcrete basement is more than three times stronger than any poured basement.

First Electrical Inspection

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Posted on August 6, 2014 by

This weeks focus was on preparing for Shotcrete…  The basic studs and lath were up, but we needed to get all the rough electrical and rebar in place.  Sherri and I had a lot of work to do.

Here is the video.

The electrical rough-in inspection must be done before the walls are closed up.  Usually, that means before drywall, but for us, it means before shotcrete. In our township, electrical inspections are done only during a few specific hours each week, so we had to catch the two-hour Wednesday morning slot or Shotcrete would be delayed to the following week.

I has carefully designed the electrical layout weeks before, and then tweaked it based on Sherri’s input. Now, Sherri and I just needed to work as quickly as we could to place the boxes, run the conduit and then finally, pull the wires thru. We used Carlon ENT (smurf tube) and I had quite a hassle getting all the boxes that I needed.  Next time, I will order in advance, but that is another story.

The process took longer than I expected, you can see I am working on it several days the week before. We still had work to do on this inspection day, so we came in very early and got going.  We had not been finished long when the inspector arrived.  He was very pleasant and actually said he appreciated that we were doing the electrical ourselves.  That was a surprise because I expected that any inspector, especially one who was a professional electrician himself, would be somewhat against the idea of home owners taking on their own electrical. He made a few small suggestions for how to keep concrete out of the openings, and handed us our “approved” inspection paperwork.

Next, Sherri and I got going on Rebar.  Mostly, I was cutting and Sherri was tying.

At the end of the day, my friend, Nate, arrived to check out the site.  He had been up from Indiana for a conference in Ann Arbor.  He reminded me that I had first told him about this idea at my dining room table nearly 6 years ago.  I didn’t ask if he thought I was crazy, then or now ;^)

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