Earth sheltered homes normally get very scaled down heating systems (some even skip them entirely). Where I live, a heating system is required for occupancy, so rather than get an expensive furnace that I would hardly use, I decided to go with an inexpensive “on demand mini boiler” hot water radiant system. I got quotes for install that were as high as $60,000, but figured I could do it for a small fraction of that, so I decided to pull my own mechanical permit and do this myself. I read a couple books and planned it out. Then I bought the manifolds and supplies from PexUniverse.com (less than 400$ for the basement).
We got it all installed and inspected (our first mechanical inspection) and then had Dysert Concrete handle the actual pour of the floor.
Installing the radiant floor was easy, but some of the recordings didn’t work out, so the final video is shorter than usual. You can read the story below for the details that wouldn’t fit in the narration.
I started with working out the layout on the computer. Building code requires that no circuit be longer than 300 ft, and most experts recommend that you balance the lengths of the radiant tubes, so you definitely want to plan it out ahead of time.
I tried a number of different plans that ran the tubes thru the hall to the various rooms, but it was just too inefficient and cumbersome to get things “zoned” well that way. In the end, I decided to drill some 5/8ths inch holes thru the base of the mechanical room wall to simplify the layout. With the right tools (DeWalt hammer drill and a long 5/8ths inch bit), that was pretty easy.
We had leveled out the pea stone after the “underground inspection”, but David helped me do some final leveling of the peastone and then Zack helped get the 6 mil plastic down. This plastic is important for keeping water vapor from the ground out of your concrete floor and is required by building code. It also helps keep the radon out, etc.
A mil is not a millimeter. Six MIL is six thousands of an inch or roughly 0.152mm. Before most English speaking countries switched from the imperial measurement system to metric, they would have called it a “thou”, based on the Germanic route word for “thousandth”, but for some reason, America decided to go “romantic” language based with this one and called it a “MIL” instead (based on the word for “thousandth” in languages like French or Italian). This is a similar etymology to how the rest of the world got the word “milli” for the Metric system, hence the similarity.
We don’t use “MIL” much in the USA, except for quantifying thin film thickness.
Since it is difficult to imagine things in thousands of an inch;
1 MIL = grocery store bag
2 MILS = Garbage Bag
3 MILS = Husky Contractor Bag
17 MILS = Pond Liner
35 MILS = Credit Card
David tossed us some sheets of insulation and we got started on the jigsaw puzzle. My rooms are unusually shaped and since they didn’t actually stock those shapes at Home Depot, we cheated by cutting pieces. We started with measuring, but usually ended up trimming each piece iteratively until it fit. We taped all the pieces together and shoved trimmings into any gaps along the wall. Not too hard, but certainly more time consuming than a square room might have been. This probably wasted about 15$ worth of insulation, so not too bad.
I marked the radiant tube layout directly o n the insulation based on that balanced plan I had carefully worked out on my computer. I used piece of scrap wood marked with the right size increments and a can of upside down surveyors paint. In addition to basic tic marks to follow, I also painted in the end loops so the whole plan would be pretty easy to follow.
Stapling the Pex tubes down was easy and fun, Sherri and I took care of most of it, but the boys were very eager to try it themselves. I imagine it would have been quite a lot more difficult (and much less fun) without that commercial grade tool we used. The tool cost quite a bit (~200$) but is very well built and I will use it a lot… I also plan to sell it and recoup most of the money at the end of the project anyway.
Connecting the pex to the manifold was straightforward and easy. There are some simple little brass connector bits and you just tighten a nut to hold it all together.
I got the Manifold, Pex pipe, the Pex stapler, staples and the pressure tester from “PexUniverse.com”. I had looked at lots of other sites (including sites that put it all together for you, such as Radiantcompany.com), but this one had the best prices and the best hardware. There are also easy to find “coupon codes”.
John (my brother-in-law) and Zack helped me finish off the third loop.
My sister Bonnie was in town and mostly helped me with the ICFs (another post/video), but she made it into this video by helping me to fill the tubes with water so they wouldn’t float in the concrete. I had been trying to pour it from the bucket into the funnel, but she had the idea to siphon it from the bucket, which was much easier and didn’t get us as wet.
Then we pressurized the system (according to building code) so we would know if anyone punctured the pipe before the concrete set.
Concrete day arrived and the guys started with putting down some six by six wire reinforcement. This was left over from the garage floor and will help prevent cracks from growing. It also helps protect the pipe and keep it all down under the concrete.
The concrete was pumped in from overhead (renting the pump truck cost ¼ of the job, but was well worth it in terms of making things go easier), and spread level. They came back an hour later and hand troweled it smooth.
In all, I paid less than 1$/sft for the insulation, radiant tube, manifold and supplies, then 3$ for the concrete work plus an extra ~500$ for the pump truck and ~1100$ worth of concrete… So, not bad.
I hope to get the “quad deck” in soon so we can put another concrete floor over this basement.
The building inspector left us a message saying that the plans were approved (pending the zoning permit which should be completed on Monday). That was really much faster than I expected. When I was in his office on Wednesday, I saw lots of sticky notes in my plans. The only one I was able to read said something about making sure that my under slab ducts drained toward an accessible point (my mechanical room). That was my plan, it just wasn’t specified in the drawings. I expected lots of discussion with him about that or other issues before he approved the plans… But now I expect I will just get the plans back with lots of notes that I will need to comply with in order to pass inspections.
Of course, now we need to pay more than $2000 to get the actual permit. On the whole we have saved about 500$ in permit fees (as I mentioned last week). So we are ahead of our budget… for now. I expect we will start to get behind again later when we need a few extra inspections due to our unusual build. For instance, we will need at least one extra rough electrical and rough plumbing inspection so we can shotcrete the basement (another extra cost associated with the basement) before erecting the walls above it and doing some more rough plumbing and electrical.
The last thing we need for the building permit is the zoning permit. The zoning inspector’s primary concern is that our property is setback 60 ft from the road. It is a little bit silly because the plans clearly show the house is more than 90 ft from the road and the stakes we put in tonight were temporary (not actually used to build) because we still need to level off the property… But anyway, it was part of the process, so we did it and it was pretty interesting.
The home is based on a circle and uses lots of angles, so I will definitely want to use a proper laser transit for laying out the footings. But at this point, it didn’t need to be very precise. Instead, I used a 2 ft paver and diamond cut the important angles in based on a paper print out (it cracked when I dropped it into position). We knew the distance from two stakes to the center of the house, so we used two ropes measured to the right distance and placed the paver, oriented to North, where the ropes overlapped. Once positioned, the large 90lb (41kg) paver will stay put. Then we measured out from the center and I sprayed my arcs with surveyors spray paint. We put stakes at key corners based on the length of the measuring tape and the angle on the center stone. My younger boy didn’t get excited about it until I sprayed the “S” for South next to one of the key points… Then he got the concept.
The final result was that we could “walk through” the rooms and get a sense of the size and flow in 1:1 scale. On that big hill with the big evening sky, the rooms felt small. We had laid out individual rooms before, but this was the first time we had really laid out the whole house and been able to walk through it. Later, standing on the far west corner of the garage and looking across the field to the far east corner of the bedroom, it looked bigger. My wife was starting to doubt that beds would fit in the rooms, but I guess we need to trust the numbers and doubt our perceptions over rough terrain (or maybe it was my rough survey skills).
I didn’t like the final position of the house. I really wanted the back window of the playroom in a certain location where the view is good and the topology of the site dips for the basement egress windows located below. In order to get that without moving a lot of earth, I think we will need to move the house north and east by ~15 ft. Next time we site the house, I may even start with the location of that window and work backward to the center of the house and then out from there.
When I setup this website, I also got an email address. Actually, it was the address that helped me pick the final website name. I liked the idea of telling contractors (or whoever) that my email address was “Simon” @ “home in the earth” dot com.
Unfortunately, things have been slow to get started and I did not end up using that email with any contractors. Since I didn’t expect any email, I haven’t checked that account since late 2012.
Well, I checked it last night and there were lots of nice comments and questions there. If you wrote to me over the last year, sorry I didn’t get back to you. I will try to get through those emails over the next few days and I will try to check it more regularly from then on.
Actually I have not told many friends about this site (Other than my wife, I don’t think anyone I know from real life has subscribed (top right column) yet. If you subscribe, you will get an email each time I post.
You can also leave comments on each page. If you just come in to the home page, you may not see the comment window. You need to click on the header for a particular post and then you will see the comment section at the bottom. If you leave an email in a comment, it will not shown on the site, but I can use it to reply.
Most earth sheltered homes do nothave a basement… This is mostly due to concerns about natural lighting, depth to the water table, etc. Structurally speaking, two buried floors would experience a lot more lateral forces from the earth. If you don’t want to rely on a sump pump, you also need to dig deeper drains, etc.
However, in my case, with a nice big hill of sandy loam soil that would have relatively low lateral forces and great drainage. I also liked the idea of using QuadDeck ICF (Concrete) flooring that would act like a “shear floor” against lateral loading. After not having the benefits of a basement in my current home, adding one seemed like a good idea to me. I just had to work out the egress exit/natural lighting and figure out where to give up space for the stairs and I was ready to go.
For the stairs, I tried a number of locations before I figured that out. I explained that process in a post a while back.
For the basement egress, since the basement was only on the North side, I had to put a window well on the north side. That was the side I originally planned to bury, but since I had such nice views there, I had already relaxed on that and put in a few windows. Now I would need to put the basement egress directly under one of those windows. Rather than a small “vertical shaft” window well, I thought it may be more interesting to put in a larger conversation pit. I could use the pit to get closer to the side of the hill and perhaps actually end up with an egress with a view, as well as a cool sheltered place to hang out.
Count the cost
While it is true that a basement is a relatively inexpensive way to gain square footage, mostly because it doesn’t need an additional roof, it does still need its own walls and floor and electrical and plumbing and that all adds up. also, the suspended floor over the basement costs considerably more than the slab on grade floor that would be needed without the basement.
Eliminating the basement would also simplify the construction process starting with a much simpler excavation, shallow drainage pipes, etc.
My specific design only called for a partial basement. I hoped to limit the complexity, but because I have a sandy site, the engineer specified a slope of 1/2. Meaning that my 10 ft deep basement will affect the construction for 20 ft around. The design with the basement required more expensive step footings, taller stem walls, two levels of french drains, etc.
On the north side, the egress window was a challenge for earth sheltering the house because I needed to be a lot more careful about retaining the earth around it. The plan looked good in 2D, but my 3D model revealed some concerns about the scale and cost of the retaining walls that will be required to keep earth from spilling into the basement.
In my original gantt chart (building schedule), I planed to spend 1/5th of my costs and a month of my schedule on the basement… Knowing that I wouldn’t have the option to come back and decide to add a basement later, and generally adding space to an earth shelteted home is difficult and because it would make a lot of my passive HVAC stuff work better, I decided to go for it.
The basement is in now and I can say that the costs were well estimated. Shotcrete went considerably over estimates, but I saved money in other areas and ended up with a fairly affordable basement in the thirty-something-dollars per square ft range for a rough basement. If I decide to plaster the walls or finish the floor, that will raise costs, but I don’t need to spend that money until I need the space. At that point, it will seem like a bargain compared to adding space from scratch.
However, I didn’t factor in what a disruption it would be on the building site, and therefore to the building schedule. The excavators and footings contractors didn’t like the step footings. I checked with the building inspector and he didn’t like them either. This meant that I was not able to do the footings all at once. Keep in mind that the basement is only under a portion of the house. I would need to backfill the basement before I could do the footings for anything else. Before I could backfill, I needed the basement shotcrete, waterproofing, plumbing, septic field (and the trench to get there), etc. Each of these things had delays, especially the septic field which slowed us down by a month due to a gravel shortage and trouble getting the septic tanks ordered. By the time we got the footings in for the rest of the house, it was pretty much the end of the summer construction season.
The silver lining is that the basement was a bit of a trial run. We got to see shotcrete applied in a less critical area of the home. The resulting mess has lead to some adjustments in the plan for the main level. If we had started with the main level, where the walls are higher and the shotcrete also needs to be applied overhead, it could have been much worse.
With lateral loading on either side of a shear wall or shear floor, the connection across that support dramatically effects the deflection in the walls. It is important that the basement wall acts like a single element from footing to the roof. If there is a joint between the basement floor and the main floor, the shear floor between them will not be nearly as effective.
(I will come back another time with some illustrations)