Reciprocal Outdoor Kitchen Roof at Tryon Life Community Farm

Overview:

This document outlines a structure to be built at TLC Farm during the summer of 2008. This "Reciprocal Roof" will replace the temporary roof structure that currently covers the outdoor kitchen on the property. This project will serve as a demonstration of sustainable building techniques and a learning opportunity while increasing our capacity as an education center. It is part of a larger infrastructure building plan currently underway. Simply put, this project consists of constructing a circular roof on the South side of the "Village Green."

WHAT IS A RECIPROCAL FRAME?

The reciprocal frame is a roof structure where each beam both supports and is supported by other beams in the roof structure. A minimum of 3 beams is required to create a reciprocal frame roof. As each beam supports the next in a reciprocal manner no internal support structure is required. Only the outer end of each beam requires support which will normally be a post used for the wall. The roof loads are transferred to these posts and in turn to the supporting foundation. The beams can be fabricated from timbers, laminated wood, steel or reinforced concrete. A very inexpensive roof structure can be made from logs. The reciprocal frame roof results in a very strong self-supporting structure with very unique features. [img_assist|nid=614|title=Reciprocal roof|desc=|link=none|align=left|width=320|height=195]

Materials & Design:

Footings: 10" poured concrete, tubular footings dug to a depth of at least 2', and rising 6" above grade. ¾" rebar extensions for seating posts. Posts: Eight skinned and linseed-oil treated fir posts. 8" to 10" in diameter. 8' to 10' in length. Outer Tension Ring: Hexagon of 8" fir poles interlocking using timber-frame techniques. This porting of the structure sits atop the posts and supports the rafters. Essentially, it serves the same function as the top of a wall in a standard framed building. Rafters: Fir poles 6" to 8" in diameter. At the inner circle, poles rest on themselves in reciprocal fashion and are notched to interlock, then bolted using heavy lag-screws and laced using steel braded cord. This will leave a 4' diameter, open circle in the center which will serve as a smoke escape for our wood-burning stoves and ovens. At the outer wall (tension ring) poles are attached using notching and lag-screws. Roofing: The triangular roof panels will be framed with lumber, decked with 2x4 materials, and covered with cedar shake. A cupola will be built over the inner polygon and covered in the same way.