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.
When you are building a house, not all the days are big days… There are lots of “odd job” days. I don’t usually setup my camera, and when I do, the footage is not usually interesting enough for a post of its own, but I thought I show a collage of odd-job days to document the gist of it.
The Video:
A little more detail:
The hardest part about these odd jobs is just to find the time for the drive out to the property. Now that the weather is cooler and I am pretty much out of vacation days, I usually wait for a warm enough day and head out to the property after work. But the days are getting shorter, so after I drive an hour to get there, I only manage to put in a couple hours of work before the sun sets. I bought some work lights to extend my time a bit before I need to pack up and head back.
As winter approaches, working around the weather is quite a challenge. The concrete weather proofing, grouting and other tasks often have a minimum temperature for correct application.
I really wanted to get the Quonset hut up sooner, but there were delivery delays. It was eventually delivered just before I had to take a 2 week business trip. I had to protect the delivery from the weather while I was away, so I laid out some plastic to keep it dry. I put the plastic down first and set the steel (all on one skid) on top of it and then folded the plastic over like a taco… The plastic at the bottom keeps the moisture from coming up out of the ground, the plastic on top sheds the rain, and the open sides were to let any moisture that did get in, get out again. I screwed wood strips on both sides of the plastic to keep in its place while I was away… It worked.
We were also in a rush to get rye grass growing before the weather got too cold for it. Actually, fall is the best time to plant grass (the air is cool, but the earth is warm), but I would have liked to start it closer to Labor Day. Sherri planted and raked in most of the seed, but I got in some rake time when I could.
The garage ends also needed insulation against the footings. The basic idea behind “Shallow Frost Protected Footings” is to thermally separate the soil under the footings from the cold air in winter so that ice “lenses” don’t form and push up the footings. The normal solution is to put the base of the footings below the “frost line”, about 4 ft deep in my area. Temperature change happens by conduction, so it doesn’t really matter how “deep” the footings are, the insulation creates a longer path for the conduction and keeps the footings warm. This building code exception to normal building practice allowed me to save a lot of money because I didn’t need to dig the footings as deep and use all that extra digging, concrete and money. Adding on this insulation is a small price to pay. Although, technically, my sandy soil means I don’t really have to worry about frost heave, the insulation is still helpful in keeping the garage temperature more stable.
This last job in the video was just cleanup… We (and the various crews who came to work on the site) had been stacking used wood and rebar on side of the building site. Now we needed to backfill that area and it was time to get that stuff out of the way. We also wanted to protect the better wood and put in under the Quonset hut. Many hands make light work… So Sherri and the boys came out to help. I really appreciate my crew.
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.
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 ;^)
