A How To Tadelakt

Lime Tadelakt is a Moroccan technique of polished lime used to waterproof primarily Earthen bathroom walls, sinks and tubs. It is similar to lime plasters around the world but is unique in that it's compressed with a stone while being treated with soap.
Read more about Tadelakt here https://ranchomastatal.com/blognewsle...

Traditionally hydraulic lime was used, as opposed to Type-S Air Lime used in this video. You can use many kinds of lime from Hydraulic, NHL3 to lime putties made from quick-lime.

Wall prep
Over substrate and then all subsequent coats, your wall should be clean, free of dust and well hydrated. Test by applying small amount of mix to wall, you should have ample amount of time to work. If not be sure to hydrate wall well, it may take up to several hours. Or try reduce amount of suction by applying an acrylic concrete bonder with water will reduce suction from existing substrate. If possible, seal room to add more humidity, allowing for longer curing times.

Step 1 – Base Coat (optional)
This does not need to be lime specifically, it could be stucco or earthen basecoat. I would skip this if going over conventional cementboard, especially if you red-guard it.
It can be applied over an earthen or masonry wall. It can take many forms, but the purpose of this step is to:
- Level and shape; and
- Give an extra layer of water protection to our walls, strawbales in our case.
Once applied, it is typically floated with wood or polyfloats to shape and level.

Basecoat Recipe
1 Part – Hydrated Lime (Calcium Hydroxide) – We used Type-S here
3 Part – Mortar Sand – the quantity will vary depending on your sand
Water – as needed

Optional ingredients:
¼ Part – Fiber – I used an Acrylic Fiber. There are many synthetic and natural fibers out there that can be replaced. I used this type as I like the size and way it mixes into the plaster.
Part – Water retainers – Methocellulose is a common one to add to thickness to your lime mix which helps slow drying time and allows for more working time. Again, there are many thickeners over the years, such as nopal (prickly pear), seaweed, blood and on. I also use Hydroxyethyl cellulose.
Pozzalon or Portland – this is to give the lime plaster a hydraulic set.
Application - can vary depending on aggregate sizes and what’s needed for base wall to get desired shape. In this video, I used sand screened through ¼ inch screen so could not be applied any thinner than ¼ inch. Most important aspect of application is to float to shape and level, using a wood or poly float, as they are more rigid than a steel trowel.

Can be left to cure completely or if you add Pozzolan/Portland mix you can apply the Tadelakt mix soon after it has firmed up.

Step 2: Tadelakt Mix
Generally applied in 1/16 - 1/8 inch layers (1.5mm-3mm). Can apply as many coats as you feel fit. I personally have never done more than 4 coats.
I only do the first coat with fiber and do not use again for all subsequent coats.

Ingredients
1 Part – Hydrated Lime
1 Part – Lime Sand in this case
Both sifted through windowscreen
Water as needed

Optional ingredients:
Pigment - often needs to be broken down by screening through mesh or dissolving in alcohol.
Fiber – refer to above. Fibers help prevent cracking but be careful with them as they can show up in finish. Make sure to leave time between coats and applying ample amount of mix. Only use in your first coat.
Water Retainer – Refer to above. Tadelakt mix is already fat because of the amount of lime to sand is very high, so you don’t need much water retainer. I like to use it to give extra water retention and a creamy, workable mix.
Pozzolan – I like using Metakaolin or white Portland

Application - usually apply between two to four coats as needed, applied very thinly with a steel trowel or float, and giving time to set-up in between coats, but not dry completely. This drying time helps the lime carbonate and lets it shrink between coats, helps guard against cracking. Floating between coats helps to align the aggregate and to level the surface. Floating is optional but just the way I like to do it.

Soaping – Use a soap high in steric acid. I use Black Olive Oil Soap in this video as it is the traditional soap used in Morocco for Tadelakt. There are plenty of other soaps that can be used however that have more stearic acid. If not already in liquid form, than grate or chop to dissolve. The soap needs to diluted with water - 1 soap to 10-20 water (I prefer more water).

Soaping needs to be done once the final coat of tadelakt starts to firm up and wick moisture. Brush the soap, at a point in curing when you won’t leave any brush marks, but not too late that the lime won’t absorb soap. Avoid drips at all costs as they will show up in finish. One pass of the soap will be enough to then start stoning.

Stoning – The purpose of using the stones is to compress the lime and to polish, which helps seal. The stone should be a hardness of Mohs 7 (or harder) on the hardness scale. Quartz or granite can be used. On top of being hard needs to have a flat surface and ideally rounded edges. It is easy to overwork and scratch, so don’t get too carried away.

Using the stones are not always necessary - you can achieve compression with very hard trowels, for example Japanese honyakis (japaneseplastering.com), which can compress like a stone.

Soaping can continue after stoning until water beads on the surface, which doesn’t take very long. Now your lime should be waterproof. If compressed and soaped it shouldn’t absorb water.

Sealers or Wax: If you want extra hardening, waterproof-ness, and gloss there is a very large selection of wax and sealers for masonry around the world. For wax, I like Canoba wax, and for sealers I used TK6 Nanocoat in this bathroom. If you want both, make sure use sealer before wax.

For workshops, check out www.caneloproject.com/workshops
Like anything this technique takes some practice to learn, don’t get too discouraged by cracks and failures, delamination and million other things that could go wrong.

Printable Document:
https://docs.google.com/document/d/1I...

For workshops, check out www.caneloproject.com/workshops