Evolution of the Vernacular Window in Nepali Architecture

The Indian sub-continental plate is pushing into the rest of Asia at a rate of 5cm per year, making it responsible for the Himalayas, and within these mountains, the relatively sheltered (until Western tourism) state of Nepal. Populations here exist in the fertile valleys and hillsides where precipitation because of moisture moving in from India occurs, contrasted with the dry, arid, sparsely populated environment on the Tibetan side of the Himalayas. The continual pressure of the sub-continental plate has resulted in much of the stone in Nepal being a compressed metamorphic rock, with slate being the most common. In construction, this is widely used as a cheap source of roofing tile, flagstones, and masonry blocks, but cannot be used for lintels (as stone in neighboring India frequently is) because of the weak tensile strength of slate. For this reason wood is used as the lintel over openings.


An additional constraint imposed on construction by the steep hillside landscape is the tendency for soil subsidence, as well as the danger of landslides and sensitivity to earthquakes. The timber window frame is adapted to incorporate these forces with an extended lintel- and sill-beam. In a typical window frame, rigidity is dependent on the strength of the glass or infill - a typical window design assumes the stability and rigidity of the wall into which it is located, whereas in the Nepali window, because of subsidence in the walls, this assumption cannot be made.


The extension of the horizontals into the stonework adds to the structural diagram of the points a, b, c, d (the typical window), the points w, x, y, z.


In a case of simple subsidence, where one side of the building moves downward at a faster rate than the other, the exaggerated diagram looks like this: between wa and bz, the construction material (brick or stone) forms a compression vector, turning the entire window into a form of bracing for the wall, and lending extra rigidity to the window frame beyond that of the stiffness of its joints.


This theory is illustrated in this photo of the failure condition. Cracking along the compression vectors indicates where the effective unit broke away as the rest of the wall subsided.


Here is the basic window type, in a rural setting; an abandoned building in the Annapurna foothills.


In urban centers, the window itself becomes a central element in the traditional urban dwelling, with the other major elements organised around it.


However as this type developed, the function provided by the window became less important with the advent of concrete, and the contemporary typology has done away with the most of the elaborations. It's unfortunate that the functionality of the window type could not be incorporated somehow into contemporary techniques.

However the religious elaborations of the window type are the most impressive, with styles developing straight out of the urban dwelling typology.