Lime Plaster Preparations

It's been a while, eh? I ended up taking off a good chunk of the summer for various reasons, but it's time to take advantage of the more reasonable temperatures and get back to work! This post is all about preparing the bathroom for lime plaster. Unlike clay plaster, lime can stand up to regular wetting once it is waterproofed with olive soap (more on that later). Below are various photos I took along the way.

Getting started at the bottom showing the tools of the trade.  

Note the short bits of lath used to provide the gap between sticks.

I placed two nails at each stud location: the first was with the nail gun,

which is quick and avoids splits in the ends.  The second was a stainless ring nai hammered by hand.

The larger head and extra gripping power is good protection against the final

wall pulling off from the studs in one big sheet.

Some areas couldn't be nailed due to the steel plates

that protect the plumbing.

This plywood section covers up the blocking that is in place
to support any cabinetry I may want to install in the future.
(I'm planning to build a bank of shelves to start with.)

Blocking between the i-joist flanges will get painted to match.
This will make  for nice finished look at the top of the wall, with the
ceiling panels sitting on top.

A temporary stop to create a clean edge for the lime.  After the wood strip
is removed, the final adobe will be toweled flush with the lime.

Making sure I don't drop any gobs of plaster  in the toilet riser pipe.

I made a small lath mock-up and spread a
test mix to see what it feels like.

I was especially curious to see how hard it is to achieve the "key",
where the plaster oozes through the slits in the lath.  Once hard,
this really locks the plaster onto the lath.

Drywall above the Windows

The interior walls, made of light straw clay (LSC), will be covered in clay plaster.  For the finish coat, I've decided to use an American Clay, pigmented product.  This should make for an easy and predictable finish coat.  I really like how informative their website is, complete with detailed videos.  Check them out at americanclay.com.

I've mentally tried out various techniques to deal with the areas above the windows and for the window sills.

This photo shows the plastic above the windows, which holds in the cellulose insulation.  This needs to be covered before I can plaster it.  Since American Clay can be applied over drywall, I decided that would be a relatively easy way to create a uniform finish coat, with a consistent look over both the LSC and the drywall.

Above the kitchen window, the drywall (and later, the finished plaster) gets notched for the I-beams, which are exposed.

This is a test section of ceiling showing the brown beams and off-white ribbed panels.

Above the closet, the beam (still unpainted here) runs along the top of the drywall and marks the top edge of the clay plaster.  The off-white panels will sit on top of this beam.

This shows the south windows.

Blowing in the Cellulose

As I mentioned in the previous post, I have no photos of me and a helper blowing in the cellulose.  It's no big loss, since the process was not terribly exciting from a visual standpoint.  My helper stood by the machine, cutting apart the bales and roughly breaking up the compressed material as it went into the blower's hopper.  Occasionally, theses chunks would create an archway over the paddles that feed the blower, and he had a stick at the ready so he could stir the cellulose and break up the arch and let the chucks fall down.  At the advice of the store employees, we kept the blower door 1/2 open, which controlled how much cellulose traveled through the hose (the airflow is not adjustable).

We did experiment opening the door further to speed things up, and the hose promptly clogged.  Lesson learned--it is a major hassle to unclog the hose!  In our case, the hose had been cut and patched in two locations, which created pinch points to initiate the clog.  We untaped the sections, beat the hose repeatedly, and raised it up to shake out the loosened material inch by inch.  All told, we probably spent an hour unclogging the hose and repairing it.  Two person-hours wasted!

I manned the nozzle, and it was probably even less exciting to watch.  I pretty much stood there and slowly twisted the nozzle while pointing it down into the cavity in an attempt to distribute the cellulose evenly and avoid having it hang up on the Light Straw Clay (LSC).  It's easy to tell when the cavity is filled up to the nozzle since the sound of the machine would raise in pitch.  It's very similar to the sound change when the hose on your vacuum clogs.

Since the stud cavities are interconnected via the thermal break between the inner and outer walls, there was a fair amount of material that would blow into adjacent cavities.  Sometimes, dust even blew out the adjacent fill hole.  For this reason, I would fill all the lower holes in a section of wall before moving to the upper holes.  In the upper holes, I'd start by pointing the nozzle down, and at the first sign that the level of cellulose had risen up to the nozzle, I'd rotate the nozzle up into the the cavity above the top plate (see photos in the previous post).  Once that area was filled, I'd slowly back out the nozzle and sweep it around to make sure there were no remaining voids.  As the nozzle was just about to emerge from the hole I'd signal my helper to turn off the blower.

It ended up taking about 7 hours to blow in 35 bags.  I was left with a bunch of 2-inch holes that were plugged with cutouts made with a 2 1/8" hole saw.

 The plugs were held in with temporary duct tape so the building inspector could see inside if he wanted to.

 After he signed off, I used construction adhesive to glue in the plugs to make them water tight and airtight.  The adhesive has been strong enough to withstand stapling on the tar paper and nailing in the shingles, with only one that came unglued.

Oh yeah, and on the same day we did this, the spray foam people installed the closed cell foam in the attic.  I have mixed feelings about the spray foam.  Its certainly not a natural building material, and it's expensive.  But it is an ideal insulator in so many ways: something around R-6.5 per inch, it seals out all air infiltration, moisture cannot condense in the insulation so it won't mold, and there is never any settling or other potential installation defects that significantly reduce the effectiveness of batts.  In this house, where I expect to be up in the the attic regularly, I thought it was the best option.  If I had an attic that was not going to be lived in or used often, I would blow in cellulose on the attic floor and just live with the 12-15 inches of depth that is required to comply with the IBC insulation requirements.

Electrical Rough-In

There isn't too much to talk about that is out of the ordinary here.  One thing I found interesting was that the electrician found it easier and faster to drill holes in the studs to route the wiring, as compared to running them within the 3" gap between the outer and inner walls.  Now that I see it in action, I can see how it's faster to pull through a hole, rather than having to hammer in staples to support the wires.  In the end, it's nice that they weren't pounding on the studs that hold up the Light Straw Clay (LSC).

 Typical wiring.  I took LOTS of pictures of everything since about an hour later, it was all disappearing behind the exterior sheathing.

 With a 3 1/4" deep box in a 3 1/2" wall, there was very little LSC behind the boxes that needed to be cleared away to give access for the wires.  Note the data outlet with the blue wire: he had to cut out the entire back of the box since the wire is so fat and can't be folded up inside like romex.  Mental note: stuff a rag in here before blowing in the cellulose or you'll get a spray of insulation inside the house.  (For the record, I DID remember!)

Sorry that the black waterline is catching your attention, but the intention was to show the neat routing where all the cables enter the service panel.  The fussy guy in me appreciates this attention to detail.  Apparently, this makes a good impression on the inspector too.  He spent more time talking about code issues with the electrician than actually looking at his work.  Another easy sign-off!  Love that!!!

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!

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.