Earthship Construction Update; plaster & plumbing

This post is an attempt to catch up with the technical details of our earthship construction activities of this summer … so bear with me as I will be touching on a number of different areas …

I wrote this post about a month ago but just got around to adding pictures and drawings today … there are many more pictures on our Facebook page.



We recently pulled our plumbing permit (end of July) for this project.  Our approach has always been that we are building a code compliant septic system with the ability to divert the flow (using 3 way diversion valves) from specific plumbing fixtures (sinks, bathtub, shower, laundry) to our grey water system.  The alternative approach would have been to design a grey water based system from scratch requiring input (and cost) from an appropriately code certified individual (engineer or certified waste water tech).  Our plumbing permit is for a standard, BC Building Code compliant septic system that easily allows us to divert the grey water flows.  This allows us to incorporate grey water into our building when the BC Building Code addresses gray water systems at some point in the future.

I have attached a copy of our plumbing permit isometric drawing to the top of this post.  I suspect this drawing is a little difficult to interpret without looking at a plan view of the earthship showing the plumbing fixtures at the same time.  (I have this drawing but still need to track down a jpeg of it … there is a floorplan drawing that may help in the photos section of  the website.)  To implement the grey water part of this system a seperate set of grey water drainage pipes were specified.  In order to remain code compliant all of these grey water pipes ultimately flow into the black water drainage system.  Three way diversion valves (we are using Jandy valves … which seem to be the most common choice for this work) allow for the flow to be sent in one of two directions; either to the septic or grey water system.

Our first implementation stumbling block occured from the use of these valves; the current plumbing code does not address grey water diversion.  As such, we will not be installing these valves initially … for the time being the grey water pipes will flow directly into black water pipes where these valves will eventually go.  This keeps our system code compliant and allows us to finish our grey water system when the BC Building Code is more clear on this topic.  The photo attached to this paragraph shows the grey water line stacked on top of the black water line with a right angle fitting at the end joining these two lines … the right angle fitting will eventually be replaced with a Jandy valve.

One struggle I found implementing this plumbing system was dealing with inconsistencies between tradiitional plumbing and grey water.  In a grey water system the preference seems to be for smaller diameter pipes for better flow (ideally not larger than 2″).  A typical plumbing system uses larger diameter pipes as the various black water flows are combined (typically 3 and 4″ diameter) … again for better flow when dealing with the solids encountered in a black water  flow.  We kept our largest grey water diversion pipe to 3″ (necessary to be code compliant for the septic system).

When we built our front tire wall we installed plumbing sleeves between the tires at the correct height to run the building septic drain line to our septic tank.  Unfortunately, we did not place these sleeves in locations that simplified the plumbing system.  We abandoned these sleeves and chose a new location for our building drain line to exit the building based on our final , submitted plumbing permit.  In order to run this pipe through the front tire wall we had to bore a hole through one of the front wall tires.  We used a sawzall to cut a hole of the desired size through the tire.  We were able to cut the tire; we went through a lot of sawzall blades, and it was a very frustrating job.  The vibration of the sawzall caused a substantial amount of the dirt packed into the tire to vibrate out of the hole that was being cut … after placing a sleeve for the plumbing pipe through the tire we re-packed the void in the tire with concrete.  Moral of the story … think twice and lay plumbing sleeves once!

We laid out all of our grey water and septic lines that will be buried under the floor or run along the walls in the bathrooms.


For the time being we only dealt with supply lines we are installing under the floor.  We ran a number of 3/4″ PEX lines from the utility room to the main bathroom.  To simplify this job we packed these lines into a 4″ diameter PVC conduit and bedded the conduit in screened gravel before burying it under the floor.  Any hot water lines were wrapped in insulation before being placed in the conduit.  The conduit was not strictly necessary; PEX can be directly buried under a slab and sleeved only where it comes through the slab … the conduit under the slab hopefully guarantees we will have no problems with these lines down the road.

Wall Plaster

Note: There are lots of pictures of what we are up to at our Facebook page (I may try and figure out how to link pictures between facebook and our website if we ever slow down … some pictures of wall plaster can be found here).

This spring we did our final tire pack outs … we did a total of about five packouts to get to the point where the walls were kind of smooth (only a little bit of tread from each tire was visible).  This was a slow job as he walls needed to dry after each packout.

We also placed ‘starter’ studs in the utility and kitchen U’s.  These studs are attached to the walls (screwed to the tires), and will act as the end points of the walls seperating the pantry from the kitchen and the utility room from the front of it’s U.  The studs were placed before the base plaster coat so that they could be used as plaster stops.

We were then ready for the base coat of plaster (also referred to as the brown coat or scratch coat).  For this job we decided we wanted some help and got in touch with Cindy Walker.  She lives in the Nelson area and has been working with earthen plasters for over a decade.  This proved to be a good decision … Cindy is very experienced and made what I am guessing would have been a very frustrating test of marital bliss seem quite simple.

The last week of July Sandra organized a plaster party and with Cindy’s help we got all of the U’s plastered. in about 4 1/2 days.  Big thanks to all of the volunteers; lots of help from family, previous volunteers and also met some new people!

Prior to plastering we screened gravel and clay through a 1/4″ screen (about 5 yards of each).  We used most of the gravel and over half of the clay for the back walls (about 1500 sqft of walls).  The mix for the wall plaster was 6 parts gravel, 4 1/4 – 41/2 parts clay, 4 1/2 parts chopped straw, 1/3 cup of borax detergent and water as required to get the desired consistency.

Our clay has a fairly high silt content (clay slip that was mixed with it settled to the bottom of the bucket over the course of a day (apparently this will take a lot longer with less silty clay).  This means that we used a lot more clay (4 1/4 – 4 1/2 parts) than would usually be required (a typical mix is apparently 4 parts gravel to 2 parts clay?).

This is the first time we used straw in a cob mixture, to  this point we have been using sheep’s wool.  I suspect you could make this mix work with wool, but we did not want any problems with our plaster coats and straw is what is typically used for the mixture.  We used 5 square bales of hay chopped through a stationary leaf mulcher we bought online from the Home Depot.  The mulcher is basically a whipper-snipper head mounted upside down in a cone; the straw is dropped into the top, passes through the whipper snipper and chopped straw drops out of the bottom.  We found that with fresh cutting cord installed on the head we got good results (pieces about 1″ in length).  As the cord got shorter with use we had to run the hay through the chopper twice to keep the straw lengths short enough.

The borax is added to prevent the straw from going mouldy as the walls are drying out.

We mixed using two small cement mixers (two to produce enough plaster to keep the people plastering busy).  We mixed the clay and sand together first … adding the materials and enough water to keep it hydrated such that the plaster was not clumping in the bottom of the mixer. After, the borax was added; the borax was added to a cup of water and stirred before being added to a mixer.  Finally, the chopped straw was gradually added.

The final mixture was unifrom and spread easily  If the plaster was too dry the plasterers had to work very hard to smear it onto the walls and trowel it smooth, if it was too wet the plaster would drop off the walls.

The base coat was hand-smeared onto the walls and then troweled smooth using wooden floats.

Our base coat of plaster was about an inch thick … much thicker in places that required more smoothing!  We do not have perfectly smooth walls, they undulate where different tire diameters were used.  A ‘flat’ wall would probbly have required another layer of packout prior to plastering, or more uniform tire diameter selection back when the walls were being built (hindsight is 20/20!).

The walls have taken about 2-3 weeks to dry in fairly hot, dry conditions.  We ran fans in the rooms initially, and left all of the windows and doors open.

Earthen Floor

We are now thinking about the earthen floor.  We hope to get the base layer of the earthen floor done now before winter so that the floor has warm drying weather so that it will dry out quickly.

As currently planned the floor consists of 5 layers.  The first layer consists of 4″ of compacted, granular fill, and is already in place.

The second layer is 15 mm poly lapped 4″ and sealed.  The poly acts as a moisture/vapour barrier, and also as a radon barrier.

The third layer is a cement/perlite mix thick enough to get the minimum R12 insulation layer now required below a slab floor.

The fourth layer will be the base layer of the earthen floor (about 3″ thick).

The fifth and final layer will be the finish coat of the earthen floor (about 3/4″ thick), finished with an oil coat for durability.

Some Thoughts on Green Building Materials

I did spend some time trying to chose green building materials for these jobs … but ultimately found there were no clear winners.  You do not even have to spend a day gluing together ABS pipe to realize that prolonged sniffing of the cement cannot be good for your health.  PVC/ABS/PEX pipe, cement for concrete and rigid insulation are all pretty nasty products to produce and do not break down well in the environment when we are done with them.  I found convincing arguments for using/not using copper/cast iron/plastic in these applications and at the end of the day did not feel great about any of the choices.  I was somewhat constrained by the Building Code in terms of which materials were allowed for a given application.  My ultimate goal was to minimize the plumbing runs, using as little material as possible and also to keep to the smallest diameters possible.


Gathering momentum

You bet we are! We’ve made some fabulous progress on the earthship. If you have liked our FB page, The Darfield Earthship, you will have seen our latest pictures and updates.  Base plaster coat is now on the tires and a five-day work party helped to accomplish this.  We submitted and had our plumbing plan approved (not without some of the usual permit difficulties).  We started the plumbing (septic) and then stopped to plaster, then stopped to level floors, and now we are back to plumbing!  During the plastering my father even did some electrical work.

Chris last posted to share his thoughts on solar hot water.  He laboured over Part 7 of the building code and designed the septic and remainder of the plumbing, based on a “greywater-ready” system. In BC greywater systems are not permittable, however there is some movement going on in the building code now to move closer to allowing them.  He also designed a “solar hot water-ready” system, but of course, as this is in the future we didn’t need to submit it. We just wanted to make sure that our basic plumbing plan allowed for its integration later.

The building department didn’t react well to version #1 of our plan. These days, I don’t think inspectors actually see plumbing plans. Most homeowners hire plumbers and once a plumber is involved, no plan is required.  After a philosophical exchange about onerous regulations imposed on homeowners, and several days of re-drawing the with a more conventional “isometric”, we were finally issued the plumbing permit.

We began the septic rough in (and actually glued some sections) and began the rough in for the main bathroom.  At the same time, I was talking back and forth with Cindy Walker of Natural Plasters.  We had finally set a date of July 31st for her to come and teach us how to apply the base plaster on our tire walls.

We opened the five day work party to volunteers and family and we had lots of help including my sister-in-law, Melanie, my Dad and Gail, my brother Tom, Andrew Greer and his friend, Dustin and Nikki Chayka.  My friend Maureen came from Canmore and cooked for us. It was wonderful.  Usually during volunteer weeks I am so busy working that meals tend to be burgers and hot dogs.  Maureen served roast chicken (our home-grown chicken), venison fajitas, eggplant parmigiana, spaghetti and an array of deserts. I think it’s the first time I gained weight during an intense work weeks!

We were quite prepared for Cindy. We’d already screened six yards of dirt and eight yards of clay.  We had five bales of hay on hand.  Our leaf mulcher arrived that morning. (I should take a picture of it…never thought to.)

It took about an hour to get sawhorses set up and for Cindy to teach us how to find the right “recipe” for our cob plaster. It is a combination of dirt, clay and straw chopped to about one inch.  It would be impossible to give a recipe as it is dependant on your clay content. Our clay, Cindy, said, was a bit silty, but it seemed to work just fine.

Over the first few days Cindy trowelled and Gail and I smeared plaster on the wall ahead of her. Chris organized material and the mixing. We had one cement mixer and we rented another from Home Depot for $123 for the week.

By the end of the second day I was starting to trowel and by mid day on the third day, I was getting the hang of it.  It really makes a difference to have the right consistency. Too dry makes it difficult to get a smooth finish.  Too wet and it wouldn’t stay on the wall. It really is one of those activities that you have to play around with. Books and videos just can’t replace trial and error.

It was hard, physical work. And, as we put the plaster up, evaporation started.  It was hot and  humid!  By the fifth day the first U had already started drying.  Nine days after finishing most of the plaster has now dried.  We’ve had, for the most part, very hot days so drying happened very quickly.

By noon on the fifth day, we had completed the last U and Cindy had time to teach us a little about finish plasters and earthen floors.

We paid Cindy $300 per day plus fuel costs from New Denver, BC.  Our days lasted 8-9 hours with about an hour for lunch.  We plastered about 1500 square feet.  We learned enough that we can now plaster the interior pop can walls, which account for another 1500 square feet. This should go faster as the pop can walls are flatter than the tire walls.

Plastering pointed out to us rather graphically, that if we hoped to have earthen floors (a similar mixture to the plaster) we would have to get the base layer on soon enough to take advantage of whatever summer heat we have left this year.  After much discussion we have decided to push ahead with the floor.

We’ve spent the last few days levelling the floor inside the earthship.  Years of bringing in dirt and digging out planters left humps and dips and a few spectacular concrete puddles from pouring half tires and making pop can walls.  Our surveyor’s transit has come in very handy.  While we were leveling in the utility room, we buried the water supply and return lines to the main bathroom. We also tidied up our inbound services like the telephone and CAT5 cables and the electrical lines for future solar and DC pump for the cisterns.  The next thing we need to do is put down a vapour barrier and insulation.  We have done a bit of research and have decided to pour a 3″ concrete/perlite insulating layer (much like the foundation of the rocket mass heater). After this we will pin our hydronic pipes and then lay a 3″ base earthen floor. Since the earthen layer will take weeks to dry, we need to get moving!  The last inch is a finish earthen layer and this wouldn’t take as long to dry so it can be done a bit later in the year.

While we accumulate materials and tools for the concrete/perlite floor, we will continue with the plumbing.  The inspector wants to see the rough-in septic and vents, and the vapour barrier for the floor. We are also still figuring out one branch of the “greywater ready” system.

During all of this work we also welcomed to our family, Spencer Lee Burkholder.  My brother Tom and his wife, Stephanie, adopted him from Taiwan and he is about the cutest toddler ever!  Our kids have also been going to summer camp, but for the most part we make ask them to work with us. Chris and I have continued our consulting work and the slower summer months have worked to our advantage, as we have been putting in as many hours as we can on construction.

I can’t promise more frequent blog posts.  We are just too tired. The brevity of Facebook works best for us right now.  Pictures below!



Solar Hot Water … Don’t Make a Bomb!

I’ve done a lot of reading lately as I layout the plumbing for our home.

The funniest statement I read became the title of this post … let’s try not to kill ourselves while building our dream home!

Before I dive into the solar heated water I want to back up a bit … what I have been doing over the last few weeks is try to come up with a plumbing plan for this building.  This has proved far more complicated than I anticipated; I don’t have extensive experience in plumbing, and many of the systems going into this house are not typical.  Regardless, stuff happens and apparently it also flows down hill … how hard can it be?

The plumbing for this project includes:

  • Domestic water supply,
  • Grey water planters,
  • Septic system and associated plumbing,
  • Solar hot water heating,
  • Radiant floor heat

Domestic water supply

The domestic water supply for our house includes the following fixtures:

  1. kitchen (sink, dishwasher although we may not install one, we wanted to have the hook-ups)
  2. main bathroom (tub, sink, washing machine, toilet)
  3. ensuite bathroom (shower, sink, toilet)
  4. Hot Water (tank?)
Other than identifying the fixtures listed above I have not done a lot of thinking about the water supply yet …
A 1″ line enters our house at the back of the utility U and will probably run underground to the main bathroom before being distributed to the various fixtures listed above.

Grey water Planters

Here again not a lot of thought has gone into the final design of the planters.

We have chosen to set the highest point of the planters at the east edge of the building and slope them down to the west edge of the building.  This means the flow of grey water is set and we need to get all of the grey water from the plumbing fixtures to the east-most planter.  To accommodate this layout our bathrooms will probably be a step-up from the rest of the floor plan … this will (hopefully) give us the height we need to get the grey water to the east edge of the building.

The other choice was to set the lowest planter in the middle of the building and have the grey water run to this point from two directions … this seemed more complicated and frankly we did not plan for this early enough … the benefit of this layout would have been smaller elevation changes due to shorter travel distances (possibly no step-up into the bathrooms).

Septic System and Associated Plumbing

This is actually where I started thinking about the plumbing … unlike everything else in this building a septic system has well defined code requirements and is fairly straight forward to implement.

The waste pipe layout is complicated by the need to separate out the grey water flow from the flow from the black water fixtures and run it to the grey water planters.  In our layout the grey water flow will be valved; it will either flow to the grey water planters or out to the septic tank.  This means that we are compliant with the building code, and did not have to try and prove that we did not need a code compliant septic system for this building.  We had an existing septic tank and field on our site and to get a permit we just had to have a certified septic installer o.k. our system.

Solar Hot Water Heating

There are a lot of options to consider when using solar heat, and everybody seems to be pushing their design as the greatest thing since sliced bread.  Added to this, the BC Building code (I believe this is similar across Canada) places restrictions on what you can use … all of this makes specifying a system challenging.

For a good introduction on different solar options this article helped me.

I found the following questions (taken from the website that warns against making a solar bomb) to be helpful …

The Fundamental Questions

  • Does the proposed system operate at low temperatures? Solar collectors are not very efficient at temperatures of 180°F.
  • Has the need for storage of solar energy been considered?
  • How will excess heat be handled?
  • How will the need for freeze protection be handled?
  • What will happen if the electric power fails in the middle of the day?
  • What will happen when the power comes back on after a period of stagnation?
  • If something goes wrong, will the system fail to a safe condition
    (fail safe)?
  • How will the occupant know if the system is not working properly?

Keeping these questions in mind the first system that occurred to me was an open-loop system that relied on a thermosiphon to pump the water around.  Confused yet?  This compares to a closed-loop system with glycol (antifreeze) and an electrical pump.  Read on … it gets worse!

We have already identified the need to block at least the lower half of our bathroom windows … its a privacy thing.  It occurs to me that this window space could be ideal for solar collectors … I even picked out evacuated tube solar collectors … these babies would obscure the view without completely blocking the sunlight … sort of like frosted glass … only functional!

By placing these tubes inside the building envelope (using the window glass as a cover) we could eliminate the need for a closed glycol loop.  In fact, the system could be an open loop thermosiphon … eliminating glycol, a heat exchanger and the need for a pump … talk about elegant.  What is holding me back from embracing this design whole-heartedly is two considerations:
  1. Will the lines close to the glass risk freezing at night, or if the building is un-occupied for an extended period of time?  Our building interior has not dropped below freezing in the two years it has been standing, but we have seen frost build up on the windows … a pipe close to the windows may risk freezing.
  2. Will the system generate a lot of undesirable waste heat in the building envelope during the summer months?

I am still tossing this idea around … variations on it are used in warmer climates.

With those considerations in mind the system that is currently winning is shown in the following image.

The solar panels are on the roof so it is a close-looped system and would use an anti-freeze solution in the heat exchange loop.  The necessity for an electric pump is eliminated by using a bubble pump … a solar pump that pumps when the sun is out by establishing a thermosiphon loop.  This pump is passive in that it works when the collectors are heated by the sun and shuts down when the sun is gone … which is pretty much when you want to pump … eliminating the need for an electric pump and a controller.

The hot water tank is used for storing the solar heat.  The tank could have an electric backup element or be propane … meaning that you will always have hot water … I still have not figured out which is the better option.

Radiant Floor Heat

We plan to have radiant floor heat in the high-use floor spaces of the earthship.  My intention is to use the solar heated water for the heating loops.

I am still trying to work this out but will look something like:

This means that the hydronic heating loops will not be passive, an electric pump will be used to move the water.  I have read about using a thermosiphon loop for this, but they still had a backup pump in case bubbles blocked the thermosiphon … so I do not think making this an active loop is a bad idea.  Our intention is to use a wood gasifier to produce electricity … the gasifier will also generate a lot of heat and I see it being primarily responsible for providing heat for the radiant floor system.  I have not shown it in this diagram because I am still wrapping my head around how it will be implemented.

Still a lot more to figure out here but this is a start.

I am curious what other people have done or come up with …

I will try to keep posting my design as it evolves … I am currently overwhelmed by the slope of this task and writing about it helps to clarify my thoughts.