After digging the trench and laying the septic pipe, drain tile and earth tubes, it was time to backfill the trench. We started at the top by the house, but I didn’t record the first couple hours for some reason, but I caught enough of the rest to put this video together.
The Video
The Story
We placed the earth tubes by staking them into the side of the slope. This saved us from killing ourselves manually back-filling the trench on what turned out to be the hottest day of the year. However, it did slow down the back filling process. Instead of just pushing the dirt back into the hole, we had to carefully (and manually) backfill around the earth tubes so they would keep the right position and slope… I guess this added another couple hours of backhoe time to the true cost of the earth tubes.
I was actually surprised how the excavator attacked the problem. I guess I naively thought he would bring the dirt in from the side where the dirt had been placed… Instead, he started from the other side and dug his way down. He dug undisturbed dirt and put it in the hole under and around my earth tubes. Once the tubes were covered enough to protect them from the excavator and there was a slope for him to climb down into the trench (in the video, you can see him slip a little), the excavator was able to reach up and pull the sand from the far side, down into the trench. From there he was able to quickly move up and down the length of the trench pulling in the dirt.
Eventually, when the trench was almost full, he was able to climb out the far side and reach some of the other dirt.
At some point, Dick parked the excavator and got into the bulldozer to level off and “reshape” the hill.
At this point, the Septic field is not yet complete, so there will still be some more earth moving before the septic system is complete.
My Pink Skirt
Marty and Dick knew I wanted a flat area 4 feet up the wall to put an insulation skirt in, so they flattened and tamped the ground in that area for me.
Meanwhile, I had been doing my own work for my employer in the trailer, but when they guys took their regular lunch break at noon, I started my 1 hour shift.
The idea is trap a bubble of heat around the house with an insulation skirt or umbrella. This idea was popularized by John Hait who calls it “PAHS” or Passive Annual Heat Storage, but the idea had been fully researched by the University of Wisconsin several years earlier. You can read more about it here.
The umbrella is really supposed to be several layers of insulation with layers of plastic between. I only put in one layer of 2 inch Rigid insulation (Foamular 250) and ran it out about 16 ft (2 sheets) from the house. Since this is really more of an insulating skirt beyond the basement rather than an umbrella over my home, I didn’t feel the need to go the full 6 inches thick that I plan to over the rest of the house. Similarly, I didn’t feel the need to put several layers of 6 mil plastic in this location. Instead I just went with one layer of pretty think painters plastic. The point of the plastic is just to reduce the amount of water that can go thru this area and steal away the stored heat with its high specific heat capacity. I sloped it all way from the house and covered it over.
I will eventually overlap this skirt with the larger insulating umbrella. Our backyard patio will eventually go over this area.
For the Video:
For the Story:
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.
