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.
My sister, Bonnie, arrived in town mid-day Tuesday (after driving for 4 hours) to give us a week of her vacation time. As a kid, Bonnie was a Lego Maniac, so she was pre-wired to be really into this building project, but I also assume she came to visit me ;^)
Bonnie is competitive and a hard worker, and, as siblings, we work well together. She was eager to get started right away and things progressed quickly.
With my timelapse camera snapping a pic every 10 seconds and playing them back at 15 frames per second, an hour goes by in 24 seconds and an 8 hour day takes just over 3 minutes… So this video ended up being over 9 minutes long… (half day, 2 full days and another half day)
For the time-lapse…
For the story.
Bon and I got out there early Tuesday afternoon and started on the steel stud prepwork… marking stud locations, drilling extra holes and adding extra Tapcons to better secure the track in those locations.
Meanwhile, we hired a young guy, Robert. This was my first “hired hand”. He is planning to go into the military soon, but in the meantime, he needed some cash to fix up his car. He was a friend of a friend and we found him by posting to our Facebook friends that we were looking for young muscles to move all the dirt around last week. This was before I simply hired the excavator to do it in less than 45 minutes. By the time we heard from Robert, it was mostly taken care of, but there was still a little dirt to level and I figured I could use him to drill pilot holes for the rebar after that. These were fairly basic jobs that didn’t require too much skill or supervision and that I wasn’t looking forward to doing myself. I showed Robert the business end of a masonry bit and told him that he should check it frequently and change the bit when the corners of the “spade” wear out. I also got him to bring down some extra scaffolding and steel studs.
Bonnie and I quickly got up 5 of the 20ft studs, braced them, strapped them in and added the lath in a relatively short time. We got a 6th one in and tied it in also, which is pretty good for just a few hours out there.
Sherri and Michael also arrived to help out. After getting all his chores done, Michael really enjoyed building sand castles on top of each of the hills. (You can see him in the top of the timelapse footage).
Wednesday morning, Bonnie and I got really aggressive with that outer curved wall on the north west side. Robert started the day bringing us studs and then got back to drilling the pilot holes with the ¼ inch bit. I checked his bit at the start of the day and it looked fine, but I handed him 5 more and reminded him to swap it out when it wore down… (Play suspenseful music here.)
I was busy working with my sister to get the studs in, and noticed that Robert was taking lots of breaks to let the drill cool down, but I thought he was handling it. About an hour in, he wanted to switch to something else because the “drill had shut down”. I thought maybe it had a thermal switch to prevent damage, so we had him do some other minor things, but after half an hour, the drill was cool and still wouldn’t start up. I guess it is burnt out. These things happen, but I also noticed that the drill bit tip was worn to a smooth ball bearing finish. We sent Robert home with 1.5 hours pay for his second day. I guess I am not ready to properly manage young help while also trying to break speed records on other tasks.
Bonnie and I continued working on the outer wall. At one point, we did a check and realized that we had just run 20 ft studs the whole way and had missed a doorway in the second floor that called for us to put a 9 ft stud in that location. We left the bracing in place and just swapped out the stud. It just took 3 screws, and we were on our way again. More studs, more strap, more lath. It was our most productive day ever. We got the whole outer wall done (up to the 9 ft mark).
That night, we discussed what to do with the remaining 2 days. We decided to skip ahead and tackle the 26 ft tower so that we could have time to secure it properly. We could then go back and do other simpler sections if we had time.
On Thursday morning, I brought a simplified install sheet that showed the angles and orientations for each stud. But as we laid it out, it seemed like something might not be right. Rather than proceed in a wrong direction, we switched to the more straight forward 21 ft section. After that was complete, we decided to apply our improved lath skills and redo all the metal lath on the inner curved wall that I had done the previous week. Having that smoother internal surface will save us lots of stucco time later.
Friday was going to be a short day because we were going to pick up my older son from camp and then go down to Toledo for a Mud Hens baseball game, so we decided to start early. We had already rechecked and confirmed that the tower install sheet was actually correct. On the way in, we bought a new hammer drill (for over 200$).
This time, I bought a Dwalt D-handle SDS hammer drill and several SDS bits. These hammer drills don’t use regular bits. One the one hand, I didn’t like the idea of paying to replace my bits with special SDS bits, but on the other hand, all the new drills are using SDS bits now because everyone prefers being able to click the new bits in without needing to find a drill chuck.
But the best part was actually using the drill. It went in nice and smoothly (like butta’). This drill also had much better shock absorption, etc. Suddenly, I wished the previous drill had died sooner, perhaps I could have got that track in much quicker…
We decided to finish off the top layer of lath for the inner curved wall before starting on the tower.
The track marking and prep work went pretty smoothly (except I ran out of Tapcons again), and we soon got to work on the studs. We got the first four 9ft studs in and strapped very quickly and then we took a break before tackling the 26ft studs. I was really concerned about them, but it ended up being not much more difficult than the 20 or 21ft studs.
The studs pick up sand when we set the down, so after I got them up vertical, Bonnie would give them a good tap and let the reverberations dump the dirt on my head while I was struggling to maintain balance. That is what sisters are for. I eventually managed to get her back in similar fashion.
We didn’t want to start on another section of the tower with only a couple hours left, so we took down the strap and lath from the first wall. We redid the strap and added additional straps to the 26 ft studs…
It was a pretty good week.
Bonnie left Saturday morning, my parents are coming out to help this next week… I am still pushing towards shotcrete before the end of the month… But I know I have a lot of work between now and then.
After completing the footings, the next step was to erect the steel studs and metal lath that we would shoot the concrete (shotcrete) against. You can think of the steel studs as fancy integral formwork. I had had some trouble up front getting the steel ordered, particularly the steel studs. So I went with another company to at least get the track (including Flextrack) ordered. This let me put the track down first while I wait for the steel studs to arrive.
Basically, track is needed to hold steel studs in place. The studs hold the metal lath and the metal lath will catch the shotcrete and shape the walls.
I originally had this part of the job in my gantt chart as a 6 days’ worth of work starting the first week of May, so I started last week about 7 weeks behind. To make matters worse, I ended up working on it over several partial days spread across a week and I haven’t even started on the vertical steel studs. I would guess that by the time I am caught up on putting in the steel studs, I will be about 8 or 9 weeks behind. Winter is coming, but I will resist the pun of saying that I am working to get back on “track”.
There is definitely a learning curve, but I consider the basement as practice for the main level and I was definitely faster by the end (as you can see in video). Knowing my velocity (per ft of flex track or straight track) lets me better estimate the time (and resources) I will need to complete the main level.
Here is the time lapse video.
On to the story.
Like an ant moving a mountain, I am just doing things one bit at a time and trying not to be overwhelmed or forget anything. For this past week, the first step was preparing a simplified version of my drawings (a basic shop drawing) with just the door buck and track dimensions labeled.
Measure twice, cut once… But first make sure you know what the measurements should be. And simplifying the drawing to show just what you need does help… But make sure you also have an idea of the other bits that will interact with that or you could get yourself in trouble.
The next bit was putting together the bucks. I decided to do that at home where I have a chop saw and a garage to work in. I cut and labeled all the pieces and loaded them (un-assembled) onto my trailer. The bucks are made from 2×6 treated lumber. They are 6 inches taller than normal because I am fastening them to the footing and will come back and cut off the 6 inches at the bottom after the shotcrete walls are in place. Then I will pour a floor to make up that 6 inches.
Others might have built the walls on top of the floor, but my “wall first” approach uses the floor as a shear plane against lateral earth loads. “Walls first” also makes the shotcrete installation much easier because it covers up the joint between the wall and the floor (so they can be less picky about it) and because they don’t need to shovel the “rebound” out of the basement. Rebound is the “pea stone” and cement that bounces off the wall during the shotcrete process. It can be up to 10% of the volume of the walls, which for my basement would be nearly 4 yards. Lugging rebound out of the basement would have been hard work for the shotcrete crew and would have cost me a lot of money.
I added my generator to the trailer (needed to power my hammer drill) and headed to pick up my supply of steel. The look on the guys face when I pulled up told me he was pretty sure it was amateur hour, they told me that there was no way they could load my steel onto that trailer. I quickly told them that, “This steel order weighs 660 lbs. I already have 332 lbs of 2x6s, 55 lbs of 2x4s and the generator weighs 163 lbs. My trailer can handle 1100 lbs and my car can two 2000 lbs, so we are all good.” I had just guessed at the generator weight, but my rapid fire numbers somewhat startled the loading dock guys for a moment and convinced them that I was serious. While they were recovering, I quickly took the back and side off my trailer and unloaded the generator so they could set the pallet of steel down with the fork lift. One of the guys helped me load my generator back on top again. Still a bit concerned, they asked me how far I was going. All I could say was, “All the way.”
Sherri said I should probably never show anyone this picture (above), but I think it shows that “where there is a will, there is a way”, even if you can’t afford to look like a pro and you end up being chuckled at by a couple of loading dock workers.
My Brother-in-law, John R., came out to help me assemble the bucks. With everything pre-cut, it was pretty straight forward. We would have screwed them into place, but I forgot my hammer drill. It took more than half an hour to get three Tapcon screws in with my regular drill. That was a waste of time, so we focused on leveling the steel storage container and getting ready for more productive days ahead.
To level the 4800 lb steel container, we used a hydraulic mechanics jack to lift one side and then we stacked bits of waste concrete (that the trucks had dumped on the sand) like a dry stack foundation wall. It looked pretty cool; I should have taken a picture before we covered it with sand. The process went pretty smoothly, but it was hot & tiring work, so I really appreciated John’s help.
As a consolation prize, John went home with a really bad sun burn.
I came back on my own with the hammer drill and got to work on the steel track. The footing is full of ¾ inch stones. It is a lumpy surface to work on, and depending on the underlying stone, the drill could go thru like butter or struggle and fail to penetrate at all. I often found that moving a few inches over was easier than trying to push thru a hard spot. Sometimes I had to try 2 or 3 spots before I found a good one.
After drilling the pilot hole, I would switch to my socket drill to drive in the Tapcon screw. I quickly found that the torque setting on my drill was also helpful. If I set it above 15, the Tapcon screw heads would just snap off. Still, it was often a frustrating struggle to get the Tapcons to screw into the harder spots. I worked until I ran out of screws and my cordless drill batteries were dead.
You may think I should have planned better and brought the charger, and you would be right, but at the time, I was tired and glad to have an excuse to go home.
The next day was my oldest son’s 10th birthday. I ended up taking him out to the property to help out. Having learned my lesson, I took my dwalt battery charger with me so I could charge one battery with the generator while using the other one in my driver. On the way, we stopped and picked up some more Tapcons. I also bought a box of smaller Tapcons (3/8ths instead of ¼), to see how they compared.
My initial plan was to use the larger Tapcons on the ends of the studs and the smaller ones between, but that was hardly necessary. The smaller Tapcons were just so much easier to drill and screw than the large ones. I ended up using up the box and buying another rather than keep using the larger Tapcons. The smaller 3/16ths Tapcons also cost 35% less than the ¼ inch.
I started out using ¼ inch Tapcons which have 1160lbs pull out and 900 lbs of shear resistance. Clearly that was overkill. The 3/16ths Tapcons had 900lbs pull out and 720 lbs of shear resistance, which should be more than enough to keep the wall in place while the shotcrete is applied. For the door bucks, I used several of the large ¼ inch by 3-3/4 inch Tapcons.
For the flex track, I bought very simple track. It doesn’t have the metal straps or locks or other “structural features”. It is simply cut so that it will stretch on one side. The shape is held by screwing it to the concrete. The fancy “structural” flex track is ~$2.70/ft and the simple stuff I bought is only ~$1.19/ft.
I had marked the footings at the right radii so I could lay my track. As a novice, I pulled the track into position, the stretching was uneven. I later learned that I could get a much more precise (and rapid) curve by inserting a screw driver and twisting to widen the outside side of the track. More experience and I found that two twists in opposite directions resulted in a more level track.
The close up install video is here.
I had to go back for a third day to put in a last few hours and get the job done before my son’s birthday party this weekend.
Next step is a small job of putting together the window bucks while I wait for the vertical studs and scaffold tower to arrive. Both should arrive next Wednesday, along with some family and friends to help erect it all.
