Laying Out Grey Water Planters and Plumbing for the Earthship

This last week has been challenging; we have been laying out the grey water planters and the bathroom walls along the south face of the earthship.

The challenge has been laying out the planters and walls while making sure we still have space for kitchen counters, walkways between the rooms and everything that has got to go into the bathrooms.  This process has involved a lot of discussion and some arguments.  Sandra and I are both still alive so I guess the arguments were not too bad.

Before laying out the planters we needed to establish a direction of water flow and planter elevation.  I did not give a lot of thought to the flow of grey water through the planters when drawing the plans.  I did locate the bathrooms along the south face as I felt this would simplify the grey water layout and I think that was a good decision.  Our earthship has two bathrooms though, and this  means we considered two options for water flow; a split system terminating in the same planter, and a shared linear system.  In the split system the kitchen and common bathroom grey water would flow through two shared planters and the bathroom off the master bedroom would flow through its own planter before ending in the same planter as the kitchen and shared bathroom.  The split system was my early favourite as it meant short runs from the grey water sources into the planters.  I was quickly overwhelmed by the complexity of laying out this system.  Not having planned for this idea from the start it was hard to fit our planter layout into a split system.  We settled on a linear system that starts at the east and of the building and flows to the west end.  This system means some longer runs than I had hoped for, but it is fairly easy to understand and design.

The other consideration in laying out the planters was elevation; both with respect to all the other planters in the system, and in relation to the grey water appliances that are feeding the planters.  The appliances feeding the grey water system (sinks, tubs, …) must be elevated above the planters (you need about 1/4″ of elevation per 1′ of horizontal travel of the grey water pipes).  In our case it means one to two steps going up into the shared bathroom so that we get sufficient elevation to get the tub water to the start of the planters.  Also, each succeeding planter in the system must be slightly lower than the one before it so that water flows through the system (like an underground river instead of a stagnant pond).  Again, we sloped the bottoms of the planters approximately 1/4″ per horizontal foot of travel.

The planters are linked together with pipes located about six inches off of the ‘floor’ of each planter.  This means that the 1st planter is connected to the second planter by a 2″ diameter sewage pipe.  The pipe leaves the first planter with the bottom of the pipe about 6″ off the floor of that planter and enters the 2nd planter again with its bottom about 6″ off of the floor.  This means that the pipe also slopes 1/4″ per foot of horizontal travel to encourage the flow of grey water between the planters.  The pipes are located close to the planter bottoms so that the grey water elevation is constant in the system … no one planter is a swamp or dry.

We ran these connector pipes a year ago when we did the initial excavation of our planter space.  We used our backhoe to dig a trench along the front of the building.  We did not give a lot of thought to the size or elevation of our planters at that time … we just did not want to be hand digging the planters a year later.  Our ground is clay and rocks … making it pretty tough digging!

Because we did not set elevations or think through the size of the planters last year we have spent a lot of this week DIGGING BY HAND (I am very glad James is here).   We had to re-grade the planter ‘floors’ so that they all consistently slope a 1/4″ per foot, and we had to dig up all of the pipes and set them properly as well.  Most of this work is done now except for the last planter on the west side of the building.

We have also started forming the walls of the planters.  Again, the work we did a year ago digging the planters was not very accurate.  Most of our initial holes were wider than the intended planters.  This means that we have been forming pop can/concrete walls from the bottom of the planters up to our desired planter wall height.  Ideally, we would have been able to start the walls on the outside perimeters of the initial excavations, reducing the work and materials required.

Underneath the pop can walls that form bathroom walls we placed a small concrete footing (6″x6″).  Underneath the pop can walls that form planter walls we excavated a small trough and filled the trough with concrete before laying cans.  The footings contain engineered fibres and is a standard mix (1 part cement ; 2 parts sand ; 3 parts gravel).  None of these walls are load bearing; the purpose of the footing is to create a flat, level working surface for the walls.

All in all it has been a productive week!

End Walls Mostly Complete!

On Friday we finished the last of the pop can/concrete work on the west wall.

These walls are approximately 15″ thick; a double layer of rigid insulation (R24 total) sandwiched between an exterior and interior concrete/pop can wall.   The concrete/pop can walls are simply  concrete walls honeycombed with pop cans.  The cans serve to reduce the amount of concrete used in the wall,  reducing the cost and environmental impact of portland cement.

Back in the spring we poured concrete foundations for each of these walls.  We dug the foundations 18″ below grade.  They are 16″ wide and a total of 24″ deep (6″ above grade).  We reinforced the foundation with a double run of 10mm rebar, and placed anchor bolts in the top of the pour so that we could bolt the door framing to the concrete.  Our frost line here is closer to three feet deep.  In order to prevent frost heaving of these foundations we insulated the exterior face of the foundations (R12 rigid insulation suitable for wet locations).  The exterior insulation creates an FPSF (frost protected shallow foundation).  Despite the fact that the footing is not below the frost line the insulation effectively raises the frost line at the perimeter of the building.

When we started the east wall back in the summer these side walls seemed fairly simple … they are only seven feet wide after all.  We worked on the east wall in bits and pieces, using it as fill-in work when we were between other construction tasks so we did not really get an idea of how much time we spent on it.

We started the west wall right after we ordered the windows and have been working on it since then … so we have a better idea of how much time and effort we spent.  We built both walls essentially as described in Earthship Volume I.  We started by framing the door opening.  We (once again) glue-laminated 2×6 T&G decking to make 2×12 planks for this job.  The door framing is a double layer of 2×12 laminated together, making for a pretty hefty door frame … I know where I will be standing in the unlikely event of an earthquake in the Kamloops region!  The 2×12 width is required to support the 15″ thick concrete walls.  We covered the framing on the exterior and concrete wall faces with 15# roofing felt as a moisture barrier.   We then nailed stucco mesh on the concrete wall faces to give the concrete a rough surface to adhere to.  Finally, we cut and placed a double layer of rigid insulation in the middle of the wall.

The concrete used for this job is a 3:1 mix of sand and portland cement.  We tried to make a very stiff mix of concrete so that we could  form the wall without the concrete mix simply slumping out of the wall cavity.  We got better at this with practice … regardless of how stiff the concrete mix you can only place about 1-2′ of wall height before you have to stop and let the concrete set up.  Note that the concrete will need longer to set up as the temperature drops … we pushed this in the last couple of days with temperatures close to freezing (that is to say I said lets keep going), and I found myself covered in concrete and pop cans.  The concrete beneath my work area had not set, and all of it slid out of the wall.  Kind of disconcerting … you do not expect an apparently solid wall to fall apart.

Once we got above the doorways we roughed in electrical wiring for interior and exterior lights at the doors, and we framed in a window above the door.  The window frame is shaped and placed so that it will be above the small roof we plan to place over the door to protect the entry from rain and snow.

The concrete work is labour and time intensive; you spend a lot of time mixing and placing concrete, and waiting for things to dry so you can keep going.  We filled in the waiting time with other small jobs.   I would guess that the concrete work took us the better part of a week.

Eventually, we plan to add an entryway ‘air lock’ on the west side of the building as we see this door being used a lot in the winter.  This means that there will be a double door here to minimize loss of heat when entering and exiting the building.

The Front Wall … Re-Evaluating our Choices

With the roof mostly done, we have started thinking about finishing the greenhouse wall.

The tire work, bond beam, and basic framing for this wall is already done.  So at the beginning of the week we started to size and order the 1″ insulated, double pane glass units.  We identified two companies in Kamloops that supply sealed glass units, and  we also started framing the support blocks for the glass.

We did not get very far though before concerns about the front face glazing as specified in the Earthship volumes stopped us in our tracks.  I have spent a fair amount of internet time researching earthship construction projects, and the glazing  (a fancy way to say glass) seems to be a fairly common problem spot.  As described by one owner/builder,

WARNING: Michael Reynolds’ mullion design for slanted glass panes (external window ‘clamp’ metal), as presented in “Earthship” Vol. 1, not only leads to leaks into the house but will continually require maintenance, do nothing to alleviate condensation drips, AND they’re ugly.


The possible concerns seems to be twofold; the potential for leaks on the exterior face, and the potential for moisture condensing on the inside face to run down into the wooden framing and the plaster covering the tires.  In all fairness, I have also read people’s posts stating that they do not have issues with water condensation, or that it occurs but it is not a very big deal.  The Earthship volumes do specify using a redwood for this framing (like cedar), which is very rot resistant and handles moisture well.  However, we did not use cedar (we used spruce/pine as this was available to us), and all things being equal we would like to avoid rot and moisture stains on the wood and the front face plaster if we can.

Our solution for this concern seems to be to install an extruded aluminum glazing system onto our 3×8 front face stud wall.  These glazing systems simplify the exterior flashing work, and provide interior gutters to catch condensation drips before they reach the wood framing.  This convenience comes at a price and it looks like the materials for our job will be in the neighborhood of $3500.00 dollars (I am still evaluating potential suppliers).  We plan to install this package ourselves.  This is not an expense we had planned on as the materials specified for this job in Earthship Volume I would probably cost around $500.00 dollars.  However, the cost is not huge, and in the long term we hope it wall pay off!

My bigger concern has been the delay this introduces into the building project.  I can be fairly linear when focused on a task, and I was all set to focus on front face framing OVER THE NEXT TWO WEEKS.  The earliest we can expect to get the glazing system is TWO WEEKS FROM ordering it and we still have not placed an order.  On top of that we will probably not place the glass order until we have installed this system and that means ANOTHER WEEK waiting for the glass.  This means that we will not have our front face exterior finished by end of September earliest, and more likely SOME TIME AT THE BEGINNING OF OCTOBER.  I am getting tense just writing about it … waiting was not part of the plan!

Fortunately, my common sense has come to the rescue.  We have lots of other things to do in the meantime and we can switch our focus to these things.  I just have to remember to take deep, calming breaths occasionally.  Strangely, my common sense looks and acts a lot like Sandra, and has been speaking to me in a loud, irritated voice lately when I talk about my original schedule.

So! Other than thinking about the front face glazing we have started mudding the interior tire walls, framed the west exterior popcan wall, and continued working on the east exterior popcan wall.  Christie (a childhood friend of Sandra’s) and her daughters (Sophie and Maya) helped us with the first packout of mud and cans between the tires in the living room … thanks guys!

We have had a fair bit of rain over the last couple of days and the good news is that there are no leaks in the roof (other than the unfinished skylights)!  The water drains really well off of the roof along the three canals that we placed at the back of the roof.  Unfortunately, the concentrated flow of water from the canals is causing some erosion at the back of the berm.  The canals simply stop at the edge of the berm as we have not installed cisterns, and we need to do something temporary to further direct this water.  We will probably do something before too long …