Preparing substrate for tadelakt

The key with most plasters is to have a good quality substrate, and this is especially true with tadelakt. Here are the steps to prepare your substrate for tadelakt, starting with a framed wall.

Over a stud frame
1. Hang cement board – leave roughly 1/8” gap for expansion / contraction.
2. Fill gap at joints with thinset, allow it to dry.
3. Cover joints with mesh tape / mud with thinset. Allow to dry.
4. Scratch a coat of thinset over whole surface (fairly coarse scratch – mix thinset a little dry).
5. Add 1/2” of cement-lime (or lime) to provide ‘suction’ – a reservoir for water. Apply flat and evenly with a square trowel.
6. Sponge surface of this absorptive base coat when it is partly set up – use the sponge to roughen the surface for adhesion of next coat, and to help level the surface.
7. Wait at least a week for the coat to cure.

Kerdi is first layer in this tadelakt sink

Kerdi is first layer in this tadelakt sink

In wet areas such as showers use waterproofing layers. I recommend Schluter Kerdi fabric because it can easily be added in the usual prep layers. Complete steps 1-3 above, then
• coat cement board with thinset (use a slightly wetter mix than usual) and
• lay Kerdi fabric over top, press out any bubbles. Follow all directions for using Kerdi fabric, including the use of unmodified thinset.
• Scratch with thinset over Kerdi, then
• Trowel on cement-lime layer as described above (steps 4-7).

 

A layer of thinset is followed up by 1/2" of cement-lime

A layer of thinset is followed up by 1/2″ of cement-lime

Tadelakt sink

Tadelakt sink

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