Bathroom Tadelakt

Tadelakt is not a well-known term.  Simply put, it involves making lime plaster water repellent by working in olive soap.  It is an ancient Moroccan technique that is simply gorgeous within a certain aesthetic.  For more info, you can learn a lot from an internet search or image search.  Feel free to start with this link.

 For better or worse, I am not at the level of craftsmanship to create a showpiece: I am basically treating tadelakt as a substitute for conventional tile because it is a low carbon, natural material.  I wanted the walls to have some color and not all pigments are "lime safe", and I found Earth Pigments to be a great resource.

This shows the final layer of plaster, including the green pigment, being applied to the north wall, below the blocking for the cabinets.  This layer is a couple millimeters thick (about 3 credit cards), which made it much simpler to mix.  Instead of the mortar mixer, which takes an hour to clean, I could do it in a 5-gal bucket.

With such a simple wall, I was done applying the plaster by 10:30.
It took the rest of the day to apply the olive soap, although it was not a continuous process.

FYI, I bought my olive soap from Black Soaps.  The info that comes with the product describes it as a very versatile product, so although I only used 1/10 of the little tub I bought, I'll be able to use it to clean throughout the bath, kitchen, windows, silver items, copper pots, the barbecue, boats, etc.  They even say it makes a great pet soap!

I used a four-step process:

1. Brush on a 1:20 mix of olive soap mixed in hot water. Polish vigorously with a semi-precious smooth stone.  This step was pretty time consuming (about 2 hours) and actually involved some muscle.  Take frequent breaks to avoid repetitive stress injuries.  Unfortunately, I didn't allow myself enough time to find a proper stone.  This is probably why my tadelakt isn't as shiny as many of the photos I see.  That's not important to me, though: I took a local rounded river-rock stone that had one nearly flat side and polished that one side to be reasonably smooth with wet/dry sandpaper.  Pretty low-tech, but it worked.  I found that my plaster dried pretty quickly, so my polishing was more to burnish the surface of the plaster, rather than to smooth out the larger irregularities.  I was never expecting a shiny, flat surface like a marble counter top, but I'm happy with the slightly irregular, mottled texture.
2. Brush on a 1:15 mix.  I used an older 2" natural bristle brush that was somewhat frayed and not suitable to cutting in clean edges anymore.  This quality, coupled with a circular motion worked well to ensure that the soap penetrated the complete texture of the plaster, rather than just sitting on top of the high spots.  I did another light polishing with the stone, just to be sure there were no remaining high spots.  Each layer dries progressively slower than the last.  After the first coat, the the top of the wall was  ready for the next coat by the time I finished at the bottom.  The second coat dried a little more slowly, so I used a small plastic bag filled with flour to smooth out the wet spots of olive soap so it would dry consistently
3. I didn't have to wait long between coats 2 and three: enough time for a snack, stretch, and sit-down.  The third layer was a 1:12 mix and took more time to work in with the flour bag.
4. By the time the 4th coat came around (also 1:12), the olive soap was sitting on the surface quite a while.  I'd brush on a section around 3-4 square feet, then move on to the next section.  Then I'd backtrack and use the brush to lightly smooth out the olive soap and move on to the third section.  Back tracking again, I'd smooth out the first section with the flour bag, and move on.  After the fourth section, the olive soap had mostly dried, but I'd do a final wipe-down with the flour bag to ensure there were no more wet spots.  Progressing in this way, I'd be working on 4 sections simultaneously.

After the walls were done, it was on to the floor using the same processes.  The only major differences were that this layer was about 3/8" thick (the max thickness for air to properly cure the lime), and I didn't add pigment.  Since this house is partly for demonstration purposes, I thought it would be nice to have some natural-color lime.

Note the extreme texture in the previous floor layer to ensure adequate grip for the finished layer.
I've taped the walls using a laser level to help get a level floor.

More than half done!  The left side, where the toilet goes, is level, and the shower drain on the right is depressed about 1".  I took the time on the previous two layers to depress them in order to keep the finished layer a uniform thickness.  

Done and treated with olive soap.  I used a sponge the next morning to get a rougher non-skid surface that is suitable for a shower.  There was some minor cracking, which I repaired over the next 24 hours by pressing down on the crack and smoothing out the lime.  That's one of the cool things about lime is that it is self-repairing for small imperfections  This process left the floor a little less uniformly smooth, but better to have a non-leaky floor!  

In the end, I can't expect perfection or professional results from myself since I've never done this before.  But after I take a step back, it's just fine and I end up with a special sense of accomplishment!

Lime Plaster Floor

It turns out I didn't take any photos of the lime plaster straightening coat; only videos that are too large to post.  But that's really not particularly interesting since it's basically just a reprise of the clay straightening coat, complete with burlap reinforcing over the studs to avoid cracks.  You can sort of get an oblique look: it's the darker plaster on the walls in the photos below.

A component of the straightening coat included the first layer of plaster on the floor.  I wanted to make sure the walls and floor were laid in one day so the corner joint would cure in one piece.  This should go a long way to avoiding leaks.  Given the extra stress on the floor, I've screwed down expanded metal lath with the screws tying everything into the underlying adobe floor.

EML screwed down and the floor is ready for plaster.  The EML will then be sandwiched between the first and second plaster layers.

The first layer of floor isn't 100% cured, so I knelt on foam blocks to spread my weight out.
By spreading the plaster on the un-cured first layer, I'm hoping to get a better bond between the two layers to effectively encapsulate the EML.

Second layer is complete with groves creating a good key for the third and final layer.

Overview, showing the still-curing straightening coat on the wall to the left.  The other walls only have one coat, which is fully cured with the exception of the bottom few inches.  This bit was done at the same time as the first floor layer to ensure a continuous corner joint (see above).

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.

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.