Prefabrication experiments - 110 - Structures - 1 - The A-frame

Whether early post and beam, industrialized balloon framing or recent developments in engineered wood systems, timber has a tangible relationship with prefabrication as pre-cutting, boring, notching and defining members before their use is as old as building. Along with traditional woodworking, pitched log structures defined early timber framing and vernacular architecture in many forest-rich nations.

The simple dry assembly of vertical members into form resistant structures has given us the humblest examples of inclined roofs and maybe the most notorious associated with cabin building during the 20th century: the A-frame structure. Advantageously utilizing the stability of a triangular arch as the basis for a simple skeletal form, the A-frame is composed of two oblique members (legs), forming a simple isosceles or equilateral triangle. The legs are then joined, nailed or bolted at their vertex angle and retained at their center by a horizontal cross member or a tie beam, completing the «A».

Spread out and axially aligned along their vertex, a series of A-frames organize a simple and flexible unidirectional space with open gable ends. Employed as a prototype of the secondary home its simplicity still seems to fascinate designers, architects and self-builders; it is a structurally effective, aesthetically pleasing, and straightforwardly built structural system. Habitually braced by horizontal members or purlin beams each oblique portion of the triangular based prism is anchored to ordinary foundation walls. Clad in wood planks, metal laminates or even asphalt shingles the structural advantages of the a-frame were nicely complemented by potential costs-savings, as the pitched wall was at once wall and roof. 

The A-frame components can be easily transported and adapted to any context or topography. A-frame cabins popped up in diverse snow-capped and mountainous regions of North America exemplifying the era's fascination with both leisure and flexibility. The A-frame is a lasting version of an easily deployable dwelling. Self-builds, manufactured made to measure or made to order kits integrating the simple the A-frame continue to define simple prefab and relate this simple timber structure to the fundamentals of dwelling – a simple base or ground plane, a pitched roof structure and transparent gables that open to magnificent views.

Red A-frame, Far Meadows, California