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.
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.
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.
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.