Light Straw Clay is DONE

It's drying nicely this week with dry temps in the 80s'.  The rule of thumb is to allow one one week of dry time for every inch of LSC.  In my case, that's 3.5 weeks.  So worst case, I should be ready to close in the walls on 9/21.  My test sections have dried in less than 3 weeks.  (I weighed them every day and when the weight leveled off, it's clear that they were dry.)

I can already feel a different climate inside during the heat of the day: it's noticeably cooler compared to shady areas outside the house.  Thermal mass at work!   Here are the finished interior walls:

East wall.  (I'll give you one guess which corner the bathroom is in)

South wall.  Note the plywood outside the left window: that's my rain screen, which keeps the LSC dry in rainstorms, while still allowing the wall to breathe and dry on clear days.

West Wall.  You can see some areas of pea gravel aren't 100% dry yet.  The pea gravel is the drainage layer and leveling course below the adobe floor.

North wall.  Passive solar design says to minimize window area on the northern exposure.  

Ready for Rain

With a bunch of rain in the forecast, on Thursday I screwed temporary 4-foot high plywood sheathing to the outside of the framing.  This should keep the worst of the rain off the light straw clay.  It's not the end of the world if it gets slightly wet as long as it doesn't get totally soaked.  With the top half of the wall left open and the 8" between the plywood and the LSC, there will be plenty of air flow, so I can leave the sheathing on for days or weeks at a time while the LSC continues to dry out.

Also notice the big pile of pea gravel on the left side of the shot.  First thing next week, most of that gets moved inside as the base for the adobe floor.

Nearing the end of the Light Straw Clay

There hasn't been any dramatic progress this week, buy it's nice that almost all the light straw clay infill has been completed.  There is just a little more work to do to fill in the quarter-rounds around the windows and then it's on to the adobe floor.

West wall: the only thing left are the quarter rounds at the door and the little panels above the rough opening.

This shows the mold I made my cutting out a section of 12" sonotube and screwing it on to 1x4 poplar boards.  The poplar gets screwed onto the framing and it is filled from the outside.

Not the clearest shot, but it shows how the plywood form is screwed onto the framing at a diagonal and filled from the outside.  The 1x3 diagonal bracing is muddying this particular shot.

Shot showing both quarter rounds in place.  I can't wait to see what it looks like with plaster on the rounded parts!

Three contractors at once

The other day entailed a massive amount of simultaneous activity!

In addition to the three of us working on Light Straw Clay infill,

The plumbers roughed in all the drains under the floor, and

The roofers installed the shingles and corrugated metal roof.

I'm still a little sad that the roof isn't green, but the "light stone" color is so much better at reflecting summer heat, that energy efficiency won out.

Filling up the walls

After getting through the learning curve at the workshop, the speed at which we're placing the Light Straw Clay has gone up significantly.  

Day two saw us nearly complete the entire north wall, which has the largest volume of LSC.

Turning the corner into the east wall.

Mixing the straw and the clay slip on the ground was rather tiring at the workshop!  With 2 or three people mixing, that was a reasonable solution, but with only one person mixing, this 3' x 8' table with a tarp tacked to the wall makes for a much more ergonomic experience.

Light Straw Clay Workshop

Yesterday we held our first workshop, which was all about infilling the inner 2x4 stud walls with Light Straw Clay (LSC).

 The wall is prepped: outside forms (half-inch plywood sheathing) are screwed on to the outside of the studs, electrical boxes are installed and screwed in flush with the wall, and the 1x2 strips are nailed to the studs.

 Closeup of the 1x2s which key into the LSC, effectively locking it into the wall.

Packing in the straw, which has been coated with a thick mixture of clay and water.  It's staged in the plywood bin in the foreground. 

The first two stud bays have been almost fully packed behind the forms.  Starting from the bottom and working up, it's a little tricky to completely fill the wall: how do you pack in the space behind the last form? 

 Answer: we do the last little bit from the outside to make sure the inner face of the LSC is as smooth and regular as possible.  That will make applying the clay plaster that much easier.  Note the outer 2x6 wall with diagonal bracing located within the inner cavity.

We pack sideways to engage the 1x2 strips, and fill in the last little bit in the middle of the cavity with very wet, clayey straw by hand.  Then we take off the small side forms and place a full length form to try to flatten out the hand-stuffed batches as much as possible.

 Closeup of the hand-stuffed areas.

Final LCS wall from the inside.  That looks NICE!  Note the blocking in the top of the wall to facilitate hanging the kitchen cabinets.