Specialisation course: Earth Plastering

20, 21 and 22 July 2021

First module of the Natural Coatings Monograph at Iscles 2021


  • Characteristics of earth as a building material.
  • An approach to the different uses of earth as a building material throughout history.
  • Distinction of useful land for building.
  • Composition of soils, function of the different components.
  • Fundamental principles of soil construction.
  • Main soil construction techniques.
  • Properties of soil plasters, advantages and disadvantages.
  • The use of soil for interior plastering.
  • The use of soil for exterior plastering.
  • Development of earth plastering techniques, tools and safety measures.
  • Protection and restoration of soil constructions.


  • Practical workshop on clay plastering from wall preparation to the final finish.
  • Experimentation with various types of natural earths for clay plasters.
  • Experimentation with finishing textures.
  • Formulation of mortars based on local soil.
  • Experimentation with factory-prepared earth mortars.

Course development

In order to offer a more dynamic experience, the practical part of the course will take place in the mornings, leaving the afternoons to deal with theoretical aspects, didactic excursions, discussion and the sharing of practical cases.


Theoretical part

Oriol Balliu Castanyer

self-builder, educator and bio-builder specialising in building with raw earth, founder of rocamare.com and puraterra.cat.

Nadir Sirera Oriol,

Architect and Builder based in Iscles. Specialised in Bioclimatic Architecture and Bioconstruction, working for years in the restoration and recovery of Vernacular Architecture.


Oriol Balliu y equipo Iscles

Oriol Balliu and the entire Iscles team will guide the construction work.


Day One


9:00-15:00 (with a short break)

Manufacture of mortar base with local soil and natural fibres. Execution of the base layer on stone wall: cleaning of the wall, manual application of the thick mortar, grinding with rulers or trowel. Application of different types of puraterra.cat base mortar.


17:00 - end

Recognition of the local soil, analysis of characteristics, tests for the formulation of coarse mortars. Choice of aggregates and fibres. Proportions: basic principles.

Day Two


9:00-15:00 (with a short break)

Manufacture of body mortar from local earth and natural fibres. Execution of body coat on top of the previous day’s base coat, or on top of rectified wall. Kos mortar application (body) by puraterra.cat


17:00 - end

We continue to work with the local soil, formulate a good body mortar with the available materials. Soil and aggregate screening systems. Systems for chopping straw or other natural fibres.

Day Three


9:00-15:00 (with a short break)

Manufacture of fine finish mortar with local soil. Execution of topcoat on top of the previous day’s body coat. Application of different puraterra.cat finishing mortars. Experimentation with finishing textures and other effects, sgraffito, etc. Formulation of finishing mortars, endless decorative possibilities. Stabilisation of clay mortars for outdoor use. Physics of earth walls/cladding; thermal, hygrometric and acoustic comfort.


17:00 - end

Discussions on final conclusions. Farewell and closure

Fourth Day




The course

The participation fee for the course is

300.- €

Accommodation and Meals

The price of the meals is 25€ per day, including breakfast, lunch, dinner and supper, all prepared with love and mostly from our own gardens. Accommodation can be in a shared room, teepee or single tent with bed (€10/night) or free camping with use of shower and dry toilet (€3/night).