Traditional Tadelakt

Traditional Tadelakt (as well as all lime plasters) were applied directly to solid masonry or a wood lathe structure. They would achieve adhesion thru the suction action of the water from the plaster into the masonry or plaster/lathe substrate it was applied onto.  These days cement and gypsum board surfaces do not offer the ability for the suction of water to adhere/bond to the Tadelakt. So the most common method to overcome the lack of suction onto modern  materials is to use a “glue” of sorts, either in the mix, or as a primer. 

Some manufacturers of these “lime” plasters/Tadelakt will advertise that they contain a plant based binder. The plant based binder is usually a methyl cellulose, xathan gum or diutan gum. None of which are natural nor would I recommend as an ingredient in a natural plaster. This means that the plaster they sell has lime as a filler or additive. The lime is not the actual binder. 

I personally believe it is unethical to advertise a plaster as a “lime” plaster when the binder is actually not lime at all. For example ethanol is a plant based fuel but I don’t think people want ethanol in their home. I think it would be more honest to advertise the product as methyl cellulose plaster that happens to have lime as a filler. 

Application of Traditional Tadelakt

Customer Submitted Photo of a Tadelakt Shower

For your application, if you wanted to use our products without a primer: First, make certain that the cement board has more than adequate framing behind. Make absolutely certain that the cement board cannot flex. Tape all the joints in the cement board using fiberglass tape and thin set. Just like you would for under ceramic tile. Then skim coat all the cement board using a rough tile thin set material. Go over the thin set material before it sets using a rough sponge or wooden float. This is to open up the pores and rough the surface. The open pores and rough surface give the Tadelakt a surface that will allow adhesion. This surface uses both the roughness (for a “key”) and the porosity for its adhesion. You will then apply two coats of Tadelakt as per instructions.

I would highly recommend doing a complete practice mock-up of the entire process on a scrape of cement board. Start with thin set and two layers of Tadelakt then finish with the “Savonite” (black soap and carnauba wax sealer). During the mock-up you can add pigment to determine the best color for your project. This will get you familiar with the complete process. 

To finish Tadelakt, compress and polish with a very hard smooth stone as it is setting. Do not wait until it is set! The exact type of trowel used to actually apply the Tadelakt is not as important as long as it is smooth and flat. The stone used for compressing and polishing is what will give the Tadelakt the smooth waterproof finish. Using 100% natural products is a fun centuries old adventure! There is not really a wrong way to do it, unless it fails or you don’t like it. Our commitment, at Lancaster Lime Works is to only use all natural materials. And to assist in your lime plaster success!