Since our clients did not know exactly what they wanted when they approached us, but did have two fixed ideas of what the place should have, a field for playing football and a barbeque for entertaining, uncertainty and vagueness became the strategies and the tools we used to generate the project. The topography and existing algarrobo trees determined which areas of the plot we could occupy and what was the apt location for the football field, while always regarding the site as a garden-grove we had to transform, for some particular needs, for a certain period of time. We defined a spatial and dimensional strategy that could be directly translated into a variable construction system based on one generic piece, effectively a diffuse border system, producing a permeable and variable structure that could allow gradual change as the project and our clients’ decisions evolved. A redundant, light structural system based on standard steel plates, 6000 x 300 x 4 mm (6 and 8 mm where needed), generates a three-dimensional lattice modulated every 600 mm, arranged in an L shaped plan, with the patio - barbeque as the fixed element, freely ordering the public and private areas in the two resulting bays. This lattice stands independent from the use and definition of the spaces, allowing them to vary in configuration, function and size. It implies and supports rather than determines, becoming as weak or strong as required, both physically and phenomenologically. Depending on your position within or without the lattice it becomes very present, or it apparently disappears. Although it is the structural, spatial and material system, it is not identifiable as an architectural or structural element that relates us to a house, aiming to remain undefined, a diffuse border between inside and outside, architecture and structure, material and immaterial.