Even though the Quonset hut was bolted down, the steel arch shape hut does not really achieve its design strength until it is grouted in place. With winter coming, I was under pressure to get it done quickly before the temperature dropped and the snow storms rolled in.
It is actually possible for concrete mix additives, such as plasticizers or accelerators, to accelerate the curing reaction so it will set in colder weather, but, the SteelMaster Quonset installation manual warned that such mixtures may be corrosive. Calcium Chloride, specifically, is known to release steel corroding chloride ions and should never be used with rebar, let alone the thin 20 gage steel of the Quonset hut.
The weather was generally too cold by that point, so I had bought a couple propane heaters and decided to get started before it got any colder. But then the weather changed and the forcast was for several days with highs above 50°F and lows above freezing. I headed out to the property to take care of this job…
The Video:
The Mix:
My grout mix was a simple 2:1 ratio of sand to Portland cement. I bought the 94 lb bags of Portland cement for ~10$ each. I already had lots of nice clean sand on site (my hill is made of it), so I just used the skid steer to bring some over to where I was mixing. Creating the mix with my own sand saved me hundreds of dollars over buying pre-mixed bags of cement. The third ingredient was water… I have no access to water on the site, but I had brought a number of 5 gallon buckets full of water with me. I did not use any additives.
I have often mixed small batches of concrete in a mixing tray or wheel barrow for odd jobs around the house. My biggest manual mix had been a couple sidewalk squares. But in this case, I knew I had about ¾ of a cubic yard to mix, and I knew that I would have lots of other concrete and stucco mixing jobs, so I decided to buy a mixer. I had been keeping my eye out for one for a while and ended up getting a decent 3.5 cu. ft. ¾ horse power electric cement mixer, on sale for 40% off. The majority is metal, but the barrel is a strong thick plastic that won’t rust on me. I paid about $200 dollars, but I am sure it will be worth it. Just the time it saved me on this one project probably made it worth it to me ;^)
Once I was all setup, I used a shovel to measure out the mix and then added water until it reached the right consistency. Ideally, the concrete should be sticking well to its self, and not to the mixer. However, until it was fully mixed, I was using a small shovel or the trowel to scrape off the sides and keep everything mixing.
I used a 3 gallon bucket to carry the mixed grout to where it was needed.
With the shorter days, of November, it wasn’t long before the sun set and I was very glad to have my work lights… However, the work-lights and mixer were quite a strain on my generator and it nearly stopped a few times, leaving me momentarily in the dark.
Near the end, when I was worried that I might be a little short of concrete, I started adding some scrap rigid insulation as a volume filler. I probably should have thought to do that from the start.
Quonset Hut Steel
There were a number of issues that delayed starting on the Quonset hut, including two extra weeks for delivery and I had to travel to Europe for a two week business trip… but eventually all the plans were in place and we had a nice weekend forecast (for late October), so my parents and sister (Bonnie) came down from Canada to help out.
The Video:
You can find the full video here:
This all happened about a month ago… But it takes a while for me to find the time to put these videos and blogs together… At the time, I made a short and quick video and posted it to Facebook. Generally, the facebook posts are much closer to real time and are much much shorter than the bog posts. If you are interested, you can like us on Facebook (click over here in the right hand side è)
This is the short video that I posted on Facebook a month ago…
The Numbers:
Each arch is made up of 7 pieces of steel bolted together with half inch bolts. Each arch section ends up weighing ~240 lbs. This portion of the building is my garage/workshop and will eventually have 20 arches and be 30 ft wide and ~40 ft long. For now, I have only put up 11 arch sections because I plan to build some forms for casting concrete ribs in the back and then roll them to the front where a crane can lift them up and move them into place.
The garage steel came on 1 pallet weighing about 4800 lbs. It included 2 buckets and 2 boxes containing about ~5000 pairs of nuts and bolts. The cost for the steel/nuts&bolts/engineering/delivery was $7200.
To assemble the arches, I used the help of friends and family… No one who helped had ever done anything like it before. The first Saturday, I had my parents and sister to help for nearly 12 hours, pre-dawn to dark. We got up 6 arches, which means it took an average of about 8 man hours per arch. Actually, the second arch took 3 hours and 40 minutes, which is about 14.66 man hours… And the 6th arch took 1.5 hours or 6 man hours. That is a decent learning curve. The second Saturday is harder to calculate because I had different people who came at different times for different numbers of hours. The first arch was done by 3 people and some time was lost giving tours to arriving friends, etc. but we were starting on the second arch by 2 hours and 10 minutes later, which is 6.5 man hours. The 9th arch (the last one that we had a full crew for) took 7 guys only 35 minutes, which is just over 4 man hours.
In total, my friends and family gave me 94 man hours over those two Saturdays. If I had to pay a moderate 20$/hour, that would have cost me $1880 in labor. I never got a quote to get the building professionally assembled, so I am not sure how that compares. However much I saved, I really appreciated the help and I hope they had some fun doing it.
The Mistakes:
- There was that one piece that we didn’t overlap in the right direction… It should be OK in the end because the seam is almost at the top and we plan to cover the structure in concrete anyway.
- I was not able to get the width down to 24 inches each for the arches… I was always half an inch over. I don’t think it will affect the strength much and the extra bit was balanced on both sides, so the building is straight. The biggest problem is that the structure is already about 6” longer than it should be. I don’t yet know how I will handle it when I add the remaining arch segments and get to the end of the slab… I don’t think I want to add an extra footing to move the front wall out 8 inches. The other options include not using the last arch, or perhaps cutting the last arch… I won’t really know how big of a mistake that was until the garage is complete.
Actually, I think this drawing from the manual is a little wrong… The text says over and over again that the 24″ should be bolt hole center to bolt hole center…
The Story:
The assembly actually began on Friday. I knew we had a lot of hours ahead of us, so I asked my friend Aaron to come out and help me get 4 ribs together. It took us about an hour to get the first couple together. We timed the second couple and managed to get down to 17 minutes for each of those.
We arrived before dawn and were prepared to raise the first arch soon after sunrise. The arches went up pretty easy, for a 240lb arch of 20 gage steel. The biggest issue was really how flexible they were…
The first one had nothing to lean it against, so we braced it with wood and rope and then hurried to get the second one up to stiffen the assembly. The second arch was very difficult. I thought it was going to collapse at one point and I was seriously questioning my plan to erect this structure without any professional help.
However, as we bolted the two arches together, things started firming up. This was good because the wind started to pick up. You can see things start to move and shake in the video. I spent a lot of time stressing about the width of the arches, but it was really the wind that made me push on to get a few more arches up to increase the stiffness of the structure. The instructions said to assemble 4 sections and then tweak the building, so we moved ahead.
The 3rd and 4th sections went up pretty easily. We had a pretty good rhythm for bolting things together and it helped that the sun was out and things were warming up nicely. We now had almost a ton of steel up and the wind was not flexing it as much.
After the 4th arch, my father and I were fighting with the steel to try and get the width down to 24 inches… We just could not compress it that far. The depth was correct, and that made no sense to me.
Since I was too distracted to provide any guidance, the ladies took the initiative and started assembling the 5th arch on their own. Unfortunately, they assumed all the steel pieces were the same… which would have been right for a true Quonset, but this was an “S-type” made up of two different radius pieces. It was clearly curving too much and Bonnie realized something was wrong. She interrupted my stressing and said, “Hey are there two different radius pieces here?” Oops, I felt bad for letting them waste their time. I took a moment to explain the two different curvatures and how the pieces went together and then they got back to work.
I eventually accepted the slightly greater than 24 inch width and started drilling holes and bolting down the arches. Perhaps this was a big mistake, but I couldn’t see any other way forward.
The view from the top was nice though…
The 5th arch went up very easily and the ladies (now expert) began to assemble the 6th arch while the men bolted the 5th to the 4th. Sherri and the boys arrived just as we were getting ready to raise the 6th arch. It had been tough for me to manage all three ropes during the pull, so I was glad to have Sherri up there to help. After the 6th, it was clear that the day was ending and we wouldn’t necessarily have time to get another arch fully in place and properly secured before dark… We decided not to try and raise any more ribs that day. Instead, we just prepped for the next Saturday.
My family went home to Canada and I spent the next week trying to get enough local friends together to help me put up a few more arches before winter really set in… Many of my friends had prior commitments or were working, etc. Some could come for earlier hours, some could come later, Some could only come on Sunday instead of Saturday, etc. I was mostly concerned about not having enough guys there at one time to actually pull up the ribs. However, by Thursday, I did get enough to sign up for a fun workday in the freezing cold.
On Saturday morning, Aaron and Don showed up first. Since we didn’t have enough people to pull a full arch into place, we decided to try the “piece by piece” method. It actually worked pretty well, although it was a bit slower than the other method and we did make one overlap mistake (probably because we were rushing).
Then more friends arrived. Carl and his son Kent came with Doug, so we had an instant crew. A while later, my brother-in-law, John, arrived. Getting the arches into position with that many guys was pretty easy and then we had several pairs working on bolting things all together… The biggest bottle neck was waiting for me to anchor the arches to the concrete at the end. My previous approach had been to work bolting the ribs together, and then work on anchoring the previous arch (we kept the current arch loose so the next one could be fit over it easier). However, with so many guys bolting the arches together, it made much more sense for me to start anchoring the previous rib as soon as the new rib was up, but I still couldn’t finish before the guys got the rest of the bolts in place. We got pretty fast by the end of the day.
Next, I will need to grout the trench. The building is attached to the ground, but doesn’t have real strength until the feet are fixed in place so they can’t lean in or out.
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. That is covered in the previous post (posted later in time, but shown lower down in the list of posts because of its date).
This is how things looked after the shotcrete was finished (and we got down the drain tile)
Progress is being 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 and pretty solid 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.
I dug out several other areas for drains and to allow the radon pipe to exit…
But I still need to run the drains and radon pipes thru the rest of the structure, and I would guess that this lumpy surface will make it much harder to get the underfloor insulation and radiant floor tubes in place. I am even a bit concerned about broken pieces of concrete tearing the vapor barrier.
I have a crew lined up to get in there to chip the rest of it out, but they are not available for another week or two. And of course, this was not in the budget.
Even though the Quonset hut was bolted down, the steel arch shape hut does not really achieve its design strength until it is grouted in place. With winter coming, I was under pressure to get it done quickly before the temperature dropped and the snow storms rolled in.
I have often mixed small batches of concrete in a mixing tray or wheel barrow for odd jobs around the house. My biggest manual mix had been a couple sidewalk squares. But in this case, I knew I had about ¾ of a cubic yard to mix, and I knew that I would have lots of other concrete and stucco mixing jobs, so I decided to buy a mixer. I had been keeping my eye out for one for a while and ended up getting a decent 3.5 cu. ft. ¾ horse power electric cement mixer, on sale for 40% off. The majority is metal, but the barrel is a strong thick plastic that won’t rust on me. I paid about $200 dollars, but I am sure it will be worth it. Just the time it saved me on this one project probably made it worth it to me ;^)
