Ghosla Roof Update: Paper Accepted to CAADRIA, 2013

A paper outlining the theoretical and technical ideas behind the “Ghosla (nest) Roof” titled “Digitally Designed Architectural Form Built Using Craft-Based Fabrication: Weaving a Complex Surface as a Bamboo Reticulated Shell” has been accepted to the CAADRIA, 2013 conference of the The Association for Computer-Aided Architectural Design Research in Asia, to be held at the National University of Singapore’s Department of Architecture from May 15th to 18th this year. The theme of the conference this year is “Open Systems” which suits the collaborative nature of the Nest Roof project where digital design methodologies are combined with craft-based construction and non-industrial materials.

On site, the bamboo work has been completed, giving final form to the shell. Here are some pictures from the site –

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Ghosla Roof Construction Update

After some delays in the project, construction on the woven bamboocrete “Ghosla” (nest) roof has finally begun. The video below shows how the weaving process enables  a team of traditional bamboo craftsmen to easily construct the digitally form-found, double-curved, funicular shell using only linear measurements read out to them by the contractor. The drawing provided by Kamath Design Studio to the contractor is a plan consisting of linear dimensions along each bamboo member where that member intersects other members. The drawing also communicates the weaving scheme, that is, whether a member goes above or below another member when they intersect. Our studio provided the height above ground at each intersection to verify that the bamboo members are curving as desired, and that the shape of the shell conforms to the digitally form-found funicular shape.

While a 1:50 scale construction model of this roof had been built using the same drawing set to test the concept of weaving a complex curved surface using only linear dimensional information, the idea was so far untested at full scale.

I had outlined the concept of using weaving to build complex digitally modeled surfaces using manual methods of construction in this earlier post.

Ghosla: A Curvature Optimized Woven Bamboocrete Roof

“Ghosla” (meaning “nest” in Hindi) is a bamboocrete roof designed by Kamath Design Studio for a 150 square meter guest house unit at the Gnostic Centre in New Delhi, India.

Curvature optimized weaving: Surface paths with minimum cumulative curvature compared to a UV transformed hexagonal grid

The shape of the roof comes from a structural form-finding process dictated by the floor plan of the building and the resulting positions of the supporting columns. A RhinoScript was used to find optimized paths for woven members on this surface. The paths found using the script are those with minimum cumulative curvature passing through a given set of points on the surface. This enables the bamboo members used in the weaving to have as large a cross-sectional diameter as possible (and thus as high a load bearing capacity as possible) since they do not need to bend much and need not be extremely flexible. The advantage of using these optimized paths can be seen when comparing them (extreme right, above) to the simple UV transformed hexagonal grid (second from the right, above). The simple UV transformed grid has member paths with significantly higher curvature which will require more flexible (and thus thinner and weaker) bamboo members for its construction.

Stepping back in the design process, the design-computational reason for constructing this roof by weaving bamboo came from the need to devise a work-flow and construction methodology that would enable the construction of a digitally designed complex curved surface (the form-found roof shape) by simple manual construction techniques in a non-industrial setting. Weaving is an ancient process that is in the technological repertoire of most cultures. What makes weaving especially suited to the construction of curved surfaces is the fact that it can use linear, one-dimensional elements to produce a surface curving in three-dimensions and requires only linear measurements during construction. I have discussed the details of this in my earlier post on Weaving and Linear Measurement in Digitally Guided Construction.

The success of this digital-to-physical work-flow can be seen in the 1:25 scale model of the roof that was constructed by carpenter Ram Lakhan with the guidance of Inderjeet Singh Seera of Kamath Design Studio using linear dimensional information obtained from a 3D computer model of the woven roof. Here are some photographs of the model just before completion –

1:25 Scale Model of the Woven Bamboo Roof Under Construction
1:25 Scale Model of the Woven Bamboo Roof Under Construction

 

1:25 Scale Model of the Woven Bamboo Roof Under Construction

While there is no doubt that there will be numerous challenges that will have to be overcome during full-scale construction, the progress on this project so far shows the ability of weaving to be used for the construction of complex curved surfaces by manual means using linear dimensional information.

The bamboocrete roof that this woven structure will support will be similar to earlier bamboocrete roofs designed by Kamath Design Studio. The woven bamboo structure of the “Ghosla” roof will replace the steel and eucalyptus log trusses used to support these earlier roofs.

Exterior View of the Bamboocrete Roof at the Kamath Residence
Interior View of the Bamboocrete Roof at the Kamath Residence