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.
I thought this video was more interesting than some of the recent ones. Hopefully you enjoy it also.
The Story:
I got there a bit early and got to sweeping off my newly poured concrete, but I was really doing some last minute thinking about where the well should go. Factors to consider range from ease of hookup now, to constructing around it and eventually living with it.
The well drilling crew from Cribley Well Drilling arrived and we settled on a location they could access. They actually wanted to put it about 10 or 15 feet out from the house, but it would have made it difficult later as I tried to get equipment and trucks around my house… I had originally wanted it further around the side of the house (which is why the camera angle had been set up that way), but they didn’t think they could drive the truck over there because of the soft sand, and if they did, the well would have been too far from the building and in the way later. Eventually, they agreed to get it as close as they could to the front of the house. The main constraint was needing room for the large drill fluid recycling tank behind the well head. The final location will end up behind a retaining wall, out of the way.
I dug to level the ground for this tank and they filled it with water from the second truck.
The drill bit was a 9 inch tricone bit. As an engineer, I have worked on computer simulations for these for my companies “oil and gas” clients, so I know that these are designed for crushing rock and stone. As the bit turns, the three roller “cones” rotate to break-up and scrape away rock. Water is pumped in thru the shaft, both to cool the bit and to push the debris out the hole. You can find an animation here… It was definitely overkill for drilling in my soft sand, but it got the job done.
They started things off without water, just to locate the hole… But then they pulled the bit up again and added a spout collar to direct the drill fluid (water with a bit of bentonite clay mixed in) into the recycle tank. Sand and gravel settles out in the first section of the tank and the cleaner water/clay mixture flows over to the other end of the tank where a hose sucks it back into the truck and thru the drill shaft and down into the well again. If they didn’t recycle the water, it would take a large swimming pool worth and would make a huge mess. Every now and then they would need to dig (or dump) the sediment out of the tank.
After they drill the first piece (with the bit on the end) in to the ground, it is time to add an extension to the shaft. The $600,000 Versa-Drill rig is designed and built for streamlining this task.
It comes equipped with two hydraulically activated wrenches. First, the one at the bottom comes out of the back of the truck to hold the lower portion of the shaft still. The operator runs the drill backwards for a moment to loosen the end piece and then pulls back the “wrench”.
Then they raise the drill up to the top of the mast. The rig also has a carousel with 15 extensions (capable of drilling 300 ft with what they brought, but they can bring additional shafts if necessary). The carousel rotates the next 20ft shaft section into position and the rig screws its self in loosely. The second hydraulically operated “wrench” moves into place to hold the new shaft section still while the drill tightens into it. Then the new shaft is moved into place above the previous piece.
The lower end is threaded in with the shaft below it held in place by the lower hydraulic wrench… and the rig can drill the next 20 ft down. This process was repeated 20ft at a time, over and over. See the video.
On my site, it was nothing but sand for the first 116 ft. Then they hit gravel and it made a lot of noise… Enough to bring me out of my mobile office to see what was going on. That layer only lasted about 4 ft and they were back to sand. My neighbor, who lives higher on the hill, came to check it out and told us that he hit water after only 117 ft. Actually, the same guy who drilled my well had also done the neighbors, but with an older version of the drill rig. He said that the water table is definitely not flat.
My well didn’t reach “water bearing fines” until about 185 ft… At nearly 16$ per ft, just for drilling, that difference adds up. The guys from Cribley joked that they wanted to drill further to help pay off their new six hundred thousand dollar rig (yes, he mentioned that price several times and that Obama was letting him write it all off in one year)… But they stopped at 186ft.
The Versa-Drill V-100NG drilling rig comes equipped with 500/200 air, 3×4 centrifugal mud pump, 15 rod carousel (3½” x 20″, 9GPM water injection, built in 2″ Bowie grouter, 12K winches with job booms, hose reel, and mounted on a 2014 Peterbilt 340 6×6.
With the water table reached, they began the process of pulling out the drill, piece by piece, back on to the carousel. It was pretty much the inverse of the previous process, but went much more quickly.
The next step was inserting PVC casing into the well to keep it from collapsing. The first piece, the well intake, was special with perforations to let the water in… The rest were just 6” PVC tubes. They glued one into the next and lowered it down, repeat.
Since the 6 inch tubes were dropped into a 9 inch hole, there was still some space around the outside. Leaving this open would let sand fall down the gap and clog the well tip. To prevent this, they inserted a flexible 1” white tube into that space. Like before, they put down 20′ at a time and just pushed (without glue) one section into the next. They pushed it down to just above the water bearing layer. Actually, they did it so fast, the time-lapse camera didn’t really catch it. Once it was ready to go, they started mixing bentonite clay into a slurry and pumping it down into the well (at 35$ per bag, you can count them in the video, I didn’t want to). As they did so, they pulled up the white tube. This effectively filled the gap around the pipe with clay that would hold the pipe in place without letting water flow around it or sand get down into the water bearing fines…
Done drilling, it was time to clean up the equipment and pack up…
Overall, they ended up digging nearly 40% deeper than the 135ft that I had estimated. That increased my cost a couple thousand dollars over the initial estimate (but they have not set the bill yet and it has been over a month). On the plus side, they estimated my well was producing about 50 gallons per minute, which is quite a bit more than the 18 g/m pump that I planned to install. That means I will have more water than I need, which is a good thing. Pumping well water is also much cheaper than city water. At current electric rates, I will pay about 25¢ per 1000 gallons. My current rate for city water/sewer is about ~8$/thousand gallons. If we used the 400 gallons per day that the standard American family uses, the well drilling should pay itself off in a little over 5 years. That swells to 16 years if I include paying off the septic field (which also went about 30% over budget).
They will send a different crew to dig a trench and run water pipes to my mechanical room. A third crew will eventually install the pump and pressure tank after my mechanical room floor is poured. That will need to wait for spring.
The Mistakes:
I don’t know if I made any here yet. It probably helped that I had experts do the actual work. But if I find out about any later, I will come back and add it here. ;^)
The only think I can think of was that after the job was over, there was a lot of bentonite laying on the ground in the area… It holds the water well and stayed annoyingly squishy for days after the rain passed. I knew it would be a drainage barrier, so I didn’t want to bury it in place… Instead I decided to spread it out (with the skid-steer), thinking that might even improve the properties of my surrounding sand… However, a little of that stuff goes a long way and even spread out, it just made the sand squishy and more difficult to deal with. I should have just scooped it all up and saved it for later.
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.
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.
