Basically, the basement of our earth sheltered home was filled with approximately 11 cubic yards of concrete slag that needed to be broken up and removed so we could prep for pouring the basement floor.
It was something we have known we needed to do since last year, but were putting it off for obvious reasons.
Here is the video:
Why did this mess happen?
All this concrete was wasted shotcrete that wasn’t on the walls and should not have been on the floor either.
As you may recall, I had used steel studs to frame the basement and then placed metal lath on the inside to “catch” the shotcrete. I had been told (by the shotcrete guys) that the lath would be enough to prevent much of the shotcrete (peastone) from blowing thru. I was told to expect a thin layer of concrete on the inside, thin enough that it would break up into small fragments just by walking on it and that it would actually save me from needing to add as much pea stone later.
Watching the shotcrete being applied, it did appear that not much passed thru when it was applied at a downward angle onto the previous shotcrete. They did do it this way for the first couple levels, and actually raised a scaffold jack platform twice as they went. But then they got a bit tired and started shooting horizontally and even at an upward angle. This allowed much more shotcrete to pass thru.
The effect was cumulative with blow thru coming from so many different angles, each adding its own layer of concrete. The round central room was especially bad for this with at least 3 layers of 2 inch thick concrete across the floor.
And once the crew was working on the inner walls, there was also “rebound”, shotcrete that doesn’t stick to the wall, and “trimmings”, concrete that is cut off the wall because too much was applied in the first place.
All this concrete (that I paid for) ended up on the floor, but not in a good, “wow, you got bonus concrete floor along with your shotcrete” kind of way. On average, I would say we had about 3 or 4 inches across most of the floor (in several layers), and up to 8 or more inches near the walls, especially in the corners. It was uneven and lumpy and even had boot prints in it. The whole feeling was somewhat “war torn” and more than a little depressing.
When I setup the main level, I plan to back the metal lath with fiberglass screen. The metal lath will still provide the strength to catch the shotcrete, but the fiberglass screen will prevent any material from passing through.
Gallery
Thought I would try to put some extra pics in here…
David working on the concrete slag floor, he did a great job and filled up 33 5 gallon buckets of rubble.
David helping to tear out the old mess
And the Story.
I like to include the text of the video, along with some extra info that doesn’t fit in a narration, so that the content is google searchable.
For this job, I had hired some teens, rented a jack hammer and taken the day off work to make the long weekend even longer.
The big question was, “How would I get this slag out of the basement?” The final solution that I came up with was a Bagster dumpster that I got from Home Depot for 30$.
The plan was to load it up and use my trusty skid steer in to lift it up and out of the basement.
It took a bit of trial and error to figure out the best way to lift the bag and to empty it, but fortunately, we had lots of tries to get it right. You can see how we did it in the video.
The bagster is supposed to be for only a single use, but it held up very well, load after heavy load, for a number of days. The only tear was caused by dragging it up the rough wall in the first lift.
This first day, we were mostly focused on the edges where the thickest concrete was because I didn’t want to rent that 75 lb jack hammer for a second day. The heavy jackhammer was actually very effective on the thick concrete, but kept getting stuck in the thinner stuff. For that, the 11 lb breaker was much more effective. My Dewalt hammer drill also got a work out. At the start of the day, I couldn’t get the teens to touch the power tools, but by the end of the day, they were much more comfortable with me and the tools and were taking turns on the jack hammer.
On Saturday, my parents were in town, even though I warned them that we would be taking on the worst job of the build so far. I also hired Zack again, he was one of the teens from the day before.
My father got to cutting a slot in the footings (doorway) for the radon tube while the rest of us got cracking on the concrete slag. Our radon tube was made of a 4 inch corrugated drain pipe, wrapped in landscapers fabric to keep dirt out. It just gives radon an easy way to escape so it won’t build up under the basement floor.
Then my father and I worked on the floor drains while the others just kept right on cracking up that concrete. In order to get the slope correct from the floor drain in the central room all the way to the outer wall, we had to cut open the tops of the footings.
We had planned for holes in the footings to run these pipes, and I had even come prepared with 4″ PVC to use to form them. However, the guys doing our footings told me they brought their own 4″ corrugated drain pipe, which they nailed in place very quickly. The problem was that the flexible pipe “floated” up in the middle when the footings were poured. Instead of being a straight sloped hole thru the concrete, they bowed to the point that we couldn’t even get the 2″ pipes thru. I guess they were not used to the footings being so wide. Narrower footings probably wouldn’t have as much deformation due to “floating”. You may recall this same issue cost me time and money during several other stages of the build. Hopefully this was the last of it.
Then we came back out again on the holiday Monday, just my wife and kids. Sherri and I cracked things up with the 11 lb “breaker” and the boys scrambled to collect the pieces into the buckets. When the buckets filled up, one of us would dump the bucket in the bagster. The boys were motivated by being paid 1$ per 5 gallon bucket. They worked for several hours before wearing out.
With the big chunks finally removed, we raked the smaller bits and then brought in some pea stone, which is required by code in my area.
I came back on another afternoon with Zack and my friend Aaron to get the second half of the pea stone down and rake it all level. At one point in the video, you can see Aaron intentionally took a pea stone shower, just to see what it would feel like. I don’t think he will do that again.
The final product was a a peastone under-floor that meets building code. The black pipes are to channel radon out of the home and the white pipes are plumbing or drains. The inspector approved the work and we were able to rake the pea stone level and move on to the next step.
Next step is to get the vapor barrier, insulation and radiant floor tubes down here so we can pour the basement floor.
This video could have been about a lot of things… It could be about appropriate ways to get you kids involved in construction… Or about how I tried to hire for this basic task so I could focus on the trickier parts of constructing my earth sheltered home…
But in the end, the worked needed to get done, so I got my 10 year old to start on it one afternoon after work/school. David is a pretty good worker, but I didn’t mind him taking breaks (lots of breaks) with the bee bee gun. On another cool spring day, I went out there with my younger son. Generally speaking, they are very different personalities (Michael is also younger and therefore less suited to digging or working independently), but I was still pretty proud of how well Michael worked. He also enjoys the bb gun, but he actually spent most of the evening with me working on the rib forms (a separate video). On each of these evenings, we took a break to go walking (and shooting) in the woods.
That Saturday, the whole family came out. While I was working on welding steel arches (another video entirely), the rest of them got to digging. My wife, Sherri, did the majority of the excavation until the bedroom footings were completely uncovered.
I took the following Monday afternoon off work and came back out. This time, I managed to hire some students to excavate while a friend helped me with welding. These two teens were scratching their heads as they uncovered my footings like archaeologists with no idea of what layout to expect.
Side note here… I had some trouble with my generator (mentioned in another video) we ended up taking the carburetor apart, etc. It turned out the carb was fine. The oil level was just a tiny bit low and the “low oil” sensor was “almost” shutting things down as the oil was drawn up into the engine.
It took the teens several hours to clear the footings. My wife thought that was money well spent. Next I had them switch to clearing all the bracing wood out of the basement. We ended up moving it away with the skid steer. I offered them a 3rd job, but they were pooped and decided to go home instead.
Now that the wood is out of the basement, we can try to get these teens back to help clear the concrete slag out of there.
At the moment, the construction schedule has 3 main paths.
1) On the east side, we are getting the steel arches rolled. We can start to erect those after the excavator comes in and sorts out the grading issue, but they are waiting on the frost laws to allow them to carry their heavy equipment on the roads.
2) On the west side, I am getting the Quonset hut ready as a work shop to build the wooden forms for the precast concrete ribs.
I probably have a months worth of work on each of these sides before the paths converge on the middle.
3) In the middle of the house, I need to get in these steel posts that will support the ring beam that will eventually support the precast concrete ribs that will eventually hold up the steel arches and shotcrete that will form the radial vaults.
This weeks video is about setting up the posts for the center section.
The Video
The Story
I’ll put the story in here to provide a little more detail and to make it text searchable for Google ;^).
Working backwards:
In this region of the earth sheltered house, the load from earth above (not shown) is directed, by the radial vaults (made of heavy shotcrete over steel arches), down onto the precast concrete ribs.
On the outside edge of the house, these radiating concrete ribs (which weigh almost 5000 lbs each) are sitting right on 4’x4′ concrete pads made of strong reinforced concrete 1 ft thick. However, at the middle of the house, the high end of these ribs are set into a central tower made of shotcrete (which will carry most of the final loads) over a steel skeleton (which will carry all the loads during construction before the shotcrete is in place). This image also shows the QuadDeck ICF floor forms. When concrete is poured over these, it will help lock the steel posts into position.
The load of those 10 heavy ribs runs thru the ring beam and down the structural steel columns into the shotcrete basement wall below.
The 3D CAD model shows a nice flat surface where these pipes attach to the top of the basement wall.
The reality is that the shotcrete guys did not do a great job of squaring off the edge of this wall, probably because it was 9 ft tall and hard to reach. I needed to fix that. I setup some cardboard forms to the level the wall should be at and backfilled with hydrolic mortar. It was thin enough that it was pretty much self leveling.
The next step was to prepare the steel bases. I bought a box of scaffold bases for $4 each, but the (nail) holes were too small to fit the anchors thru. I drilled them out using the lowest setting on my drill press and some lubrication.
Drilling steel requires low speed and lubrication. I lubricated with thread cutting oil. The smallest container I could find was much more than I would need and only cost ~4$, the drill bit was 7$, so I used the lubricant generously in order to preserve the life of the bit. I found applying it directly to the bit was the best way. If the bit started to smoke, I would stop the drill and add more oil. If the speed/pressure and lubrication are correct, long spirals of metal will come off. This indicates that the steel is being cut and not just wearing away the bit.
Then it was time to head back out and mount the bases to the wall. I was using sleeve anchors that require you to drill a hole first, and then drop the anchor in the hole. It is important that the sleeve be completely below the surface. When you tighten the nut, the sleeve is expanded and presses against the sides while the nut pulls what ever you are attaching down toward the sleeve… I was in a rush and didn’t put one of the first anchors in properly. There was probably dust in the hole. But I couldn’t pull it out again either. With the sleeve too high, the nut tightened against it before pressing the metal to the concrete, so it would never be tight. Eventually, it will be under another ft of concrete, so I was not too worried about it, but I put the rest in more carefully.
I was also careful to make sure each scaffold base was level so it would be easier to plumb the columns later.
My steel posts were ready a couple days earlier than promised (a first for me on this build), so I picked them up in my trusty trailer. They weighed about 100 lbs each and put the trailer near its official limit, but it felt like it pulled easily.
The following weekend, my parents visited with my sister.
The mission was to move the steel posts into position on the base plates, hold them steady and level and then tack them into place with my welder. The first one worked pretty well. But the welder jammed on the second one. I couldn’t untangle it, so we had to cut out all that welding wire and re-setup the machine. From then on, I always checked the wire spool every time I moved the welder to make sure that it was not tangled.
This third post was the one on the less stable base, so we added extra bracing to keep it plumb until the concrete is poured around it. We had a lot of experience pluming steel last summer, so everyone knew exactly what to do and it only took a minute or so.
My sister and I both enjoyed the welding, so we took turns welding vs holding… Some times on the same post if it was tricky to access a certain point. The most time consuming part of the process was simply adjusting the scaffolding, etc. so we could reach what ever we needed to reach.
It took us about an hour to get the first 5 posts in, but they were on the side of the circle that was easy to reach. We were expecting the back side, were we had to balance on the wall, to be more difficult, but it was pretty easy too.
After all the posts were in place, I was worried that someone may give these a good push and cause them to shift… Yes, they are welded to steel plates bolted into strong concrete with 3 inch steel anchors, but an 8ft long 100lb lever would probably be able to pry those out.
I wanted to weld the ring beam on right away, but each half was 320 lbs and I couldn’t think of a safe way to get them into position.
So we decided to weld some rebar between the posts as a temporary solution. This was nice and easy and I really liked the look of it, so it will be sad to have to cut most of it off again when we need to put the door bucks in.
I was not sure how far my tank of shielding gas (Ar and CO2 for the MIG welder) would go, so we only did tack welds. That turned out to be a good decision because it ran out just before we were done. Without the gas, the final few welds looked pretty ugly.
After that, we put in some work prepping the shop for building the forms, and I will talk about that another time.
The next step in this center section will be getting in the QuadDeck ICF (insulated concrete form) floor over the basement. I am having a painful time getting that scheduled.
The rest of the steel arches are still being rolled and I will soon start on the forms for the ribs.
This first day, we were mostly focused on the edges where the thickest concrete was because I didn’t want to rent that 75 lb jack hammer for a second day. The heavy jackhammer was actually very effective on the thick concrete, but kept getting stuck in the thinner stuff. For that, the 11 lb breaker was much more effective. My Dewalt hammer drill also got a work out. At the start of the day, I couldn’t get the teens to touch the power tools, but by the end of the day, they were much more comfortable with me and the tools and were taking turns on the jack hammer.
The final product was a a peastone under-floor that meets building code. The black pipes are to channel radon out of the home and the white pipes are plumbing or drains. The inspector approved the work and we were able to rake the pea stone level and move on to the next step.
