Our work on Mas Palol near Girona/Catalonia began in 2012. At that time, working with clay plaster was practically not present in Spanish construction business and we, as a well-known, experienced clay plaster specialist, were asked by the Spanish company Casa Alternativa Xavi Puig for support in the application and execution of clay plasters for the inside and outside of a wooden two-story building.
I was happy to get Prof. Dr. Christoph Ziegert Dipl. Ing., a globally recognized specialist in building with clay and author of excellent specialist books, to become part of our team for this challenging project. In the application for execution, we prevailed against the competition from France.
Our job was to plan and carry out the interior and exterior clay-based plastering, the façade calculation, Tadelakt in the bathrooms, and general advice. Father of the project was the holistic architect Oldrich Hozman, from whom I learned a lot during this project execution and with whom I am still in contact today. The client planned the private building presented here as part of an ecological hotel complex.
It is a two-story building made of wood frame construction on a natural stone foundation. The curved façade is a frame-slat construction calculated
The first step was facade calculations and extensive tests with the local clay that was to be used from excavating the foundation at Christof Ziegert laboratory in Berlin.
The laboratory tests we had previously carried out with the local clay had taken into account all possible options for different mixtures: with cow dung, casein, linseed-oil and local (hydraulic)lime.
The clay plaster test series focused on its suitability as an external plaster in exposure to the harsh climate of the Mistral winds and Alta Empordia intensive rain and the lack of suitable local sand for the necessary mixing with clay.
The facade calculations were based on the assembly of laminated birch wood strips on site (!) to enable the organic shape of the facade. As a plaster base, a wicker was originally planned under the guidance of Emmanuel Heringer.
For the facade construction, Christof Ziegert based his calculations on a plaster load of around 300kg/m2 (!). On the one hand, this is due to the sheer weight of the clay plaster. The clay plaster should penetrate through the wicker to the rear and, due to the curvature, had to be calculated in three layers with a total thickness of about 10cm. The assumed load calculation when wet due to rain (an additional 20 kg for 10cm of clay plaster) and under wind load (here an additional 100kg/m2) does not appear to be made out of thin air, since when dry, the 10cm thick plaster layer already weighs 165kg/m2.
Given the exposed nature of the façade in the harsh climate with intense rainfall in the Alta Empordia and its strong Mistral winds, we were very concerned.
Ultimately, I no longer wanted to risk the responsibility for clay-based exterior plastering on the facade for the following reasons:
a) due to unresolvable defects in the façade assembly which became more and more present and significant during the ongoing assambly. The carpenter work carried out was evaluated by the specialist construction supervision as “not suitable for the intended clay plaster”, b) concerns about the suitability of the clay as a facade coating with sufficient protective function for the wooden structure facing the direct exposure and the local climate and c) an increasing estrangement with our Spanish partner company after an expert report from a local engineer was launched in which Christof Ziegert’s calculations were relativized as conservative and did not attach importance to the concerns expressed.
The facade was later plastered with -as far as I know- hydraulic lime by another company from Barcelona.
To carry out the interior plastering, we mainly worked in a team of four EMBARRO workers, using our PUTZMEISTER P11 worm pump plastering machine and a mixer that premixed sand, clay and a small amount of finely chopped straw. The powerful plastering machine with diesel engine allowed us to transport our plaster mixture from its fixed place in front of the house to the farthest corner on the upper floor. The continuous supply of material with a spraying machine made it easier for us to create the curved surfaces, which had to be applied in widely varying material thicknesses and yet evenly.
To be able to plaster the solid wooden frames of windows and doors and the wooden surfaces of the ceilings, commercially available reed rolls (with a large distance between the individual stems) were previously attached (with stainless steel brackets) to the wooden paneling of the ceilings and in the area of the window and door reveals. Fixing the reed rolls as a plaster base to the wooden substrate with the rust-proof brackets every 6-8cm took much more time than processing one layer of clay plaster on walls and ceilings.
Because of the curves, the design was made in at least three, sometimes four layers of clay plaster, each minimum 1cm, in certain occaissions up to 3cm thick.
The first layer created a base, the second layer approximated the desired shape. Jute fabric was incorporated into the surface of the second layer, which cost us a lot of effort on the ceiling because jute is so loose that it is difficult to adapt to a shape.. The third layer allowed the final shaping. The entire building is designed sharp edges. With clay plaster it was easy to model any shapes due to its plasticity.
The client wanted a special shade of yellow for the final coloring with clay paint. For this we designed a mix of local clay with mineral “gold ochre” pigments and casein from KREIDEZEIT.
We sprayed the relatively thick clay paint with compressed air over the clay plaster surfaces and thus removed the last imbalances from the curves – or created new ones 🙂
We carried out the Tadelakt work in the bathrooms, including sink, bathtub, shelves and floors, with KREIDEZEIT Tadelakt lime.
The detailed, time consuming preparatory work for the 2mm Tadelakt coating and the lime plaster in the wet areas were done by the Xavi Puig team with its curved organic design by the architect Oldrich Hozman.
At this point in time we were still carrying out flooring and “stressed surfaces” with Tadelakt, but experience has taught us in the meantime that this does not meet the general requirements in the long term, especially as the customer would have to undertake a regulary, special maintenance effort that is hardly feasible in practice.
We also learned that the “KREIDEZEIT Tadelakt” product quality is more for decorative coatings and less appropriate for stressed surfaces. But even with stronger traditional lime mixtures based only on weakly hydraulic lime and selected sands, comparable with original Marrakech Tadelakt lime, I no longer want to recommend the execution of floors and kitchen worktops with Tadelakt.
The amount of work required for the complex details of the curved constructions demanded each of the companies involved, and many of the individual solutions were almost experimental in nature.
Conclusion: an extraordinary project that you only encounter once in your life. Thanks to Oldrich Hozman for the architecture, experience, patience and presence with “good vibes” on site, Christof Ziegert for the calculations of an unusual façade, insightful laboratory work and instructive on-site supervision, and -not at least- the patient customer for the courage to create something extraordinary.
The total construction time of Mas Palol was around 2 years. Depending on the construction phase, we as EMBARRO were busy with the interior work in three stages with four to five workers and construction supervison for a total of around three months over a period of six months. The total plaster work has been 750m2 of clay plaster indoors, approx 100m2 of Tadelakt finishings and endless complex preparatory and secondary work.
There are more photos of the finished interior of the house on my Instagram account. Our video of another building project provides a detailed insight into the processing of clay plaster with the plastering machine, in this case with a smaller “closed system” MP25 machine. Further thoughts on Tadelakt can also be found in another article.
There is a book in German about Oldrich Hozman’s work. This book also deals with Mas Palol.
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