Thursday, September 29, 2016

Lime Plaster - First Coat

First off, a word of caution: lime plaster is caustic and you won't even feel it burning your skin.  It's not instantaneous, so you have time to neutralize any lime that gets on your skin with vinegar (which is acidic and neutralizes the basic lime).  Keep a bucket of 1 part vinegar to 10 parts water at the ready to clean yourself at regular intervals, and your tools before the lime starts to harden on them.  Wear eye protection when mixing the plaster, thick chemical gloves when working with it, and long sleeve shirts, and long pant at all times.

This is not intended to be a complete list of safety precautions: you MUST research how to work with lime plaster safely before embarking on these techniques.  Hopefully I have instilled a respect for the material and the importance of knowing how to work with it safely.

Now, on to the fun!  There were two aspects to the first coat.  First was to coat the light straw clay (LSC).  This was done the same way as the first coat of clay plaster: take handfuls of plaster in your gloved hands and mash it onto the surface of the LSC.  The intention is to get it fully bonded into the straw; we'll worry about making it flat in the next step.  I didn't take photos of this step in-process, since it is the same as clay plaster.

LSC covered in lime plaster.  Note that the wood sill and lintel have been taped off--
a precaution that I didn't need to take with the more benign clay plaster.
 The second task was to get a coat of lime plaster bonded to the lath.  Starting from the top, each trowel-full would get worked up into the last batch.

Note that I taped off the blocking at the top of the wall to maintain a clean line.
Make sure to press hard enough to squeeze the plaster through the lath.

Plaster is finished and relatively smooth.  Grooves were cut into all plaster
with a hair pick, just as I did with the clay plaster (Thanks again for that idea, Bob!).  Those pipes are stub-outs for the shower fixture.
I didn't plaster all the way to the bottom of the wall so I could staple the expanded metal lath to strengthen the
wall-floor transition.  I'll want to make this in one continuous pour  to minimize the potential for leaks at the corner.

Thursday, September 22, 2016

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.