thumb|A tadelakt-covered wall
Tadelakt () is a waterproof plaster surface used in Moroccan architecture to make baths, sinks, water vessels, interior and exterior walls, ceilings, roofs, and floors. It is made from lime plaster, which is rammed, polished, and treated with soap to make it waterproof and water-repellent. Tadelakt is labour-intensive to install, but durable. Since it is applied as a paste, tadelakt has a soft, undulating character, it can form curves, and it is seamless. Pigment can be added to give it any colour, but deep red is traditional.
Constituents and chemistry
The basic constituents of tadelakt plaster are:
- lime plaster (not Portland cement)
- in some cases, marble or limestone sand (but not other aggregates)
- natural soap (often "black" or olive oil soap) to speed carbonation of the surface and impart water-resistance.
The soap chemically reacts with the lime plaster, forming lime (calcium) soaps. Calcium soaps are insoluble in water, and fairly hard. The restoration of riads in Morocco has led to a resurgence in its use.
In modern times, it has been used outside.