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.
An inspection is needed before back-filling. Inspections in our township are limited to Monday, Wednesday or Friday, 10:00 AM to noon. And you are required (ideally) to give the inspector two days notice. Sherri and I had already got the waterproofing up and started the drain tile the weekend before, so on Monday, I scheduled the inspection for Wednesday morning and scheduled Roe Brothers Excavation for Wednesday afternoon. The plan was to complete the drain tile on Monday or Tuesday evening, but we had thunderstorms…
My sister (Bonnie) visited us from Canada again, arriving by motorcycle late Tuesday night. I am sure she was thrilled to hear that we would be getting up again at 5:00 AM. We had to get out to the property by first light in order to be sure to get the drain tile in before the inspector arrived.
Drain tile
They call it “drain tile” because it used to be made of clay tiles, curved like Spanish roofing tiles. Now days, it is much better to buy long plastic tubes. Special drain tile PVC is probably better to use because it has smooth walls and lays straight, but I used the corrugated HDPE pipe instead, primarily because of the price and because it is easy to lay around curved walls. I admit that the corrugations are not ideal if you want water to drain out of the tiles completely. I bought drain tile with a sock around it because it was only 5 cents more per ft (it is 50 cents more per foot with the sock if you buy it at Home Depot, so don’t buy it there).
Having to lay the drain tile is a little frustrating because, with all the sand on the site, drain tile is totally unnecessary. We have gone thru many storms in that excavation and have seen that water just falls thru the sand and the water table is not a problem. However, drain tile is required by code. A fellow builder in the same sandy area told me that he put in the drain tile to pass the back-fill inspection, but didn’t actually run it anywhere to drain. Even the building inspector told me that he doesn’t expect my drain tile will ever carry any water.
However, I am the kind of guy who likes to do things right anyway. I spent a lot of time making sure that my drain met the required slope all the way to daylight. This required a lot of digging to lower or raise the ground level.
The building inspector also insisted that we follow the building code requirement to cover our drain tile with 6 inches of pea stone and cover that with landscapers fabric. This would have been great on my current house which is built in clay… Research on the internet showed that it was best to lay the landscapers fabric down first, then lay the tube and gravel and cover it with the other half of the fabric like a very crunchy burrito. The truck delivering the pea stone couldn’t get very close because he was sinking in to our sand (irony?), so we had to carry 4 yards (actually only used 3 of them) down to the footing by bucket.
To make these drain tiles worth all the effort, I decided to use them as bonus earth tubes. This required a change in the layout. Instead of a loop around the house and a single tube draining to daylight, I made it a circuit with both ends draining to daylight… That took an extra hundred and fifty ft of tube that I will run down the same trench as the septic pipe. Actually, I took it one step further and connected the high end of the tubes into my house. Sherri thinks this is a terrible idea because the air traveling thru the tubes could be picking up mold from the corrugations. The fact that it passes thru the septic trench doesn’t help. I think it was fairly low cost and has minimal risk and I can seal it if she turns out to be right.
Back to the Story…
This lugging pea-stone was the fun part that Bonnie arrived just in time for. My wife and boys also carried their fair share of pea stone that morning. The work goes by quick in the timelapse video, but it took several hours in real life. Then we closed the landscapers fabric and waited for the inspector.
He arrived and took a careful walk around. I was expecting him to check the slope, but he seemed content with a visual inspection. I guess it was obvious that it dropped by a ft along the side of the footing. He did comment that my drain tile burrito was strange because most people just lay the landscapers fabric on top of the pea stone, not under it… We passed that part of the inspection.
Waterproofing?
The inspector was much more concerned about my waterproofing.
I didn’t want to use the stinky tar that is commonly used in my area. It is dirty and smelly and a pain to put up. Other “board based” waterproofing is expensive and much better suited to smooth flat walls. I ended up going with an “elastomeric penetrating sealer”. The install was covered in this post. This stuff sprayed on with a paint sprayer, but quickly soaked in and dried clear… Other than slightly darkening the color of the concrete, you can’t even see or feel it. At a microscope level, it has actually affected the chemical structure of the first quarter inch of concrete to lock out the water… And the elastomeric part will actually bridge cracks to keep them sealed (so they claim).
Anyway, I can’t blame the inspector for questioning a new type of waterproofing that he had never seen before (and still hadn’t really been able to see). He asked for literature on the waterproofing, specifically, if it had passed a certain test. I said I had seen the tech specs on line and they talked about this being for above and below grade waterproofing of foundations and basement walls. I could send him links that evening (in the mean time, Sherri actually got them on her smartphone while on site).
Meanwhile, I had a crew coming to back fill right after lunch.
The inspector decided to give me a “provisional” pass. I could proceed at my own risk. If the waterproofing turned out not to be acceptable, construction would need to stop until I dug it up and reapplied waterproofing so I could pass this inspection. Ouch. But I was pretty confident that basement waterproofing sold at Home Depot would pass. Surely, I couldn’t be the first person to try to use it? Dun dun dunnnn!!!
Back to the Story…
After lunch, the excavators arrived to back-fill. We had made it quite clear that we needed this fill to be well compacted because other footings will go on it. I also marked the 4ft level along the walls and told them to stop at that point so I could put in earth tubes and rigid insulation. They put the sand back in in lifts, each just over 1 ft, and then tamped like crazy with a mechanical tamper.
In this pic, I let my older son go in to help rake even though my wife was very nervous about him being down there while the excavator was running.
Earth tubes
Earth tubes have been central to my plan since the beginning. You can see these pages about earth tube design. So it felt great to finally be putting them in. It was also great to have my hard working (and digging gifted) sister to help me out. The primary earth tubes are 8″ double wall HDPE pipe that run over 250 ft down the hill to daylight. They cost about 6 times what the 4″ corrugated pipe costs, but they are stronger, have a smooth inside and 4 times the cross sectional area. The pipe I bought was “earth tight”, rather than “water tight”, just to keep the cost down.
We sloped the pipes at 1/4 inch per ft, which required digging into the freshly compacted sand. The difficulty of digging actually made me feel better about how well compacted the sand was. It took us past dark to get the work done.
This pic shows that we had to cut the pipe and join sections with 30 degree and 45 degree bends. Everything locked together without need for screws.
The next morning, we got Marty (from Roe Brothers Excavating) to compact over the earth tubes for us.
On the other side of the house, we put in shorter earth tubes (average 75 ft) between the house and the window well (as the low point). Here I experimented a bit. I did put in two more of the 8″ double wall HDPE pipes, but I also put in a 6 inch corrugated HDPE pipe and a 4 inch Corrugated HDPE pipe.
Last (and probably least), I put in a 1″ solid pipe (it was actually intended as irrigation pipe). I have had the opportunity to computer model a system for a researcher in India who is working with a system of 1″ earth tubes. His physical model is producing good results so far (he has asked me not to show his results until he publishes his paper). My biggest objection is that the 1″ pipe actually costs about the same as the 4″ pipe, but you would need 16 of them to get the same cross sectional area. There is also the issue of greater back-pressure thru smaller pipes. The benefit is supposed to be much greater surface area, and therefore better heat exchange, so you can use shorter pipes… I am looking forward to the conclusion of the research, but wanted to test my own.
I used hydrolic cement to seal the pipes into the holes I had made in the basement wall. I also filled the area around the connection with pea stone so that water couldn’t sit there.
Back to the Story…
Once the pipes were back in, back-filling and compacting proceeded as before.
At certain times, Bonnie and I laid down Foamular 250 rigid insulation to help trap heat in the volume of earth around the basement. I will talk more about that another time…
The back-filling isn’t completely done, first we need to finish the trench down to the septic tank, and then we can back-fill on that north west side of the house.
Before we can back-fill against the basement, we needed to clear the area, waterproof and put in the drain tile… We also needed things like radon tubes and floor drains to exit the building.
My wife, Sherri, had to help a lot this week… And as she puts it, “It wasn’t princess work!” I did try to hire some people, especially when I realized I would have to carry down and place the 4 yards of pea stone by bucket, but it didn’t work out and we were on our own.
The video is here…
Stripping
I started with stripping the bracing away. In most cases the wood was perfectly good with only a few screw holes. I will get to use it all again on the second floor. Actually, the site has only generated a couple bags of garbage and a box for recycling all summer, and that was mostly lunch trash dropped by the contractors working on the site.
I left the insulation on the side of the window well. It was meant to be forming, but with an earth sheltered umbrella, it helps to insulate the earth where ever you can.
Waterproofing
We bought a power sprayer from home Depot (Graco Magnum X7), which worked pretty well. We justified the purchase by reminding ourselves how much work it had been to paint the ceilings in our current house when we moved in. This sprayer will come in handy when we do one last paint before we put our existing house on the market next spring. As for the current task of spraying on the waterproofing, we saved a lot of time (and got better coverage) by not trying to roll the water proofing over that rough surface. With only one sprayer, it was a one person job and Sherri took care of it.
As for the water proofing its self, we used ProteShield Elastomeric Waterproofing Sealer. We actually applied it about 50% thicker than the directions specified. The instructions said it would dry clear, but we were surprised that it appeared to “disappear” after just a few minutes (and faster on smoother sections of the wall). It was like it wasn’t even there.
When we got the waterproofing inspected later, the building inspector was concerned about it. He gave us a “partial” pass, and told us we could proceed at our own risk, but if the waterproofing doesn’t qualify, we will need to dig it up and do it over again. We proceeded with the back-filling on faith in Home Depot and (later that evening) sent him this technical data sheet, which mentions that it is for above and below grade waterproofing of basements and foundations. It even says to give it 48 hours to cure before back-filling, we gave it double that. However, the inspector says it is missing a mention of some specific government tests that would qualify the waterproofing for use as below grade waterproofing. The inspector is going to try and contact the company to see if they have this documentation, and if not, he is going to insist that we redo it.
Drain tile
I suppose drain tile used to be made of ceramic tiles curved into tubes and then fired. In hispanic areas, I have seen them use the same tiles they use on the roofs. These were placed end to end to help carry water away from foundations. Now days, they are made of HDPE plastic that lasts forever. Ours was also covered in a nylon sock to keep the sand from clogging it.
Actually, our site doesn’t even really need drain tile. The sand just lets the water fall thru it, but the building code says we need it and that we need it to be covered in pea stone (an extra cost/hassle that shouldn’t be necessary for such a sandy site).
Another neighbor in the area told me that he put in the drain tile around his house to satisfy the inspection, but then didn’t actually run it to anywhere, since that part is not actually inspected.
I agree that these drains will probably never carry water, but I decided they should at least do something. I am going to use them as earth tubes to carry fresh air into the house. Sherri doesn’t like the idea of carrying fresh air thru corrugated pipes because water can sit in them and cause problems (mold, humidity)… But I also know of many success stories. I wanted to try it out and I can always seal them up if it doesn’t work out.
The first day that we laid the drain tile, the battery died in the camera, so you don’t see how many hours it took me to get it all sloping just right.
The big hassle on the second day (Saturday) was carrying all that pea stone down into the “pit”, bucket by bucket. We didn’t make our Saturday night deadline. The inspector is only available for a few slots each week, so if we missed Monday for the pre-backfill inspection, we would need to put off the back-filling and schedule the inspector for Wednesday…
That was the the day my sister was coming into town… We would need to come back and finish up then.
Insulation
You can’t see it in the video because Nick and I were working on the other side of the basement. We initially hoped that the waterproofing would be sticky enough to “glue” it, but it was not sticky at all. So we waited for the waterproofing to dry (2 hours cure time), and then tried to glue 2 inch thick Foamular 250 to the walls using “Liquid Nails“… That didn’t work out at all because we couldn’t keep the stiff foam pressed against the curved wall long enough for the liquid nails to dry. We decided to add the insulation as we back-filled… The dirt will hold it in place very well.
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.
