House A + Structure Prototype

The principals of joining short members of wood to create longer spans in a reciprocal frame (RF) have been used since the 12 Century for floors and roofs when longer members were not available. The properties of planar RF structures were developed and exploited in the project, House A, East Wall, Dublin 3. The roof is a planer RF system sitting on three short beams of solid Douglas fir which span the width of the space. All other beams are of shorter length and are arranged in a pattern of RF Modules to exploit the square void in the centre, 900mm x 900mm. The final layer (layer C) are the Cross-laminated timber panels which create horizontal stiffness and alternating voids to light the plan. From House A, two prototype structures are developed in large-scale timber models (Scale 1:10) to demonstrate how the structure can be adapted to a variety of spatial programmes by exploiting the variety of tessellation patterns generated by the RF Modules and how it is assembled in sequential layers without the need for temporary supports. The spatial programme in Model 1 is an adaptable hall space (16m x 16m) and Model 2 is a multi-storey housing unit (10m x 10m) based on a module of 900mm. The Structure Prototypes can be repeated horizontally or extended vertically with the top floor becoming the roof. In each case, the “Bridget’s Cross” pattern generated by the sequence of RF Modules means that there are always opportunities for light, ventilation and services in the roof or between floors. In both the hall and the housing, the plan can be open or sub-divided depending on use, generating a variety of floor plans. The models use solid beech wood members and SherpaTM Mini 10 wood connectors, at the Scale 1: 10, and can be assembled from a kit-of-parts and disassembled for ease of transport. The engineering attributes of the model scale up and best demonstrate how it would be built at 1:1. The timber members for each prototype at 1:1, are designed in BauBucheTM GL75, a hardwood glu-lam product, which is a high performance material relative to its own weight. Its engineering properties to allow for slimmer cross-sections thus reducing the volume of material consumed. The width of the panels in BauBucheTM Board S (60mm) is compatible with the modular roof and floor panel (1840mm) of the prototype that also benefits material consumption. The joint is made using a surface-mounted SherpaTM wood connector, which does not involve taking a notch out the beam. Both products are standardised and compatible, which simplifies prefabrication and rapid assembly. When comparing the planar RF design using 1800mm panels with one using 10 x 16.2m long beams 1800mm apart with like-for-like materials, in this case, the RF prototype reduces the volume of material needed by 45%. The proposed structures if built at 1:1 can be disassembled and reassembled according to needs of users and could incorporate material from existing structures for re-use.