The symmetrical interior of the house is of modest proportions: 9m width, 27m length and 6m height.

It has a lineal typology, referring to the traditional harbor house : “casa chorizo”, which is divided with cedar plywood plates with walnut edge guard, being the way of distinguishing between public and private spaces. 

This feature is easy to see in "La Casa del Arroyo", where the main environment for social use constitutes an absolute spatial continuity, while the more private sectors, such as bedrooms, sanitary services and the kitchen, are clearly structured in a scheme organized by the stair arch. Therefore, the staircase constitutes a division between public, private and also service spaces. 

The main similarity between this house and the tradicional Argentine ones is on the bedrooms, since they are arranged in a row, conected to each other.

In this sense, the interior space is made up of a central volume that longitudinally separates the house into halves: the social on one side and the private on the other. But that volume is being transformed, since it is the container for the fireplace in the living room but also the closest of the bedrooms, kitchen cabinet and dividing wall in the gallery area.

Among the social spaces we find the living room: a meeting place, decorated with simplicity and with wooden partitions that provide warmth.

The musical studio: semi-public, strategically located in a corner of the house, where the environment allowed the full opening of the windows and the direct recording of the sounds of the stream and the song of the birds.

Next to it, the dining room: separated by a folding door.

On the other side of the volume, in addition to the music studio, we find the kitchen and the bedrooms, simply decorated, with overhead lighting from the skylights.

But Amancio Williams did not follow most of the characteristic patterns that define that type of houses, instead he used new technologies and materials of the time to make his own vision of the house reality.

Following this, Amancio's project has a main floor raised to the height of the treetops, whose living space is connected to the exterior through a continuous window, allowing 360º views and integrating nature in all the spaces of the house-musical studio. 

That conection with nature was the main objective of "La casa del arroyo", and the main reason Amancio designed it the way he did. In fact, after it was finished and before showing it to his family, he wrote a letter to his brother (Mario, who later got the house after his father death) as an explanation about the significance of every detail of the house. 

You asked me "why don't they put the house on a soil embankment?" With such an embankment you would create a different sensation, which would be of a natural order, but created by man, a hybrid in other words. Man should create sensations of a human order. To manufacture a false hillock is playing at creating nature and that is wrong. Plus, for the embankment, 2,000 cubic meters of soil are needed, and that is an enomous task. That wouldn't be the worst though. Rather, leaving the house resting on the ground would do away with the whole range of sensations achieved and the meaning of the project.