After the construction of ladder house and the shipping containers, the Sacred-Groves community felt the need for a space that volunteers and interns can use to do table-top activities and work with power tools. Thus came about an initiative for a workshop. A sketched out plan was made, consisting of a simple rectangular layout of 8 columns in a grid of 4m x 3.5m.
Before erecting a structure of any sort, a low height plinth was constructed using flat rubble from demolition waste. First, the rubble was laid out over the marked area completely. Cement mortar (1:8 cement: sand) was used to lay the rubble and fill the gaps. Pointing was done and the edges were made smooth.
The Primary Structure:
A column-beam structure forms a very simple load-transfer system. In this design, two beams of 10.5m length rest on four columns each. Each of these beams is made of three bamboo members forming a continuous member. Two more beams of 4m length rest in the perpendicular direction, keeping the two longer sides stable.
Eight holes of 2’ depth were made in the ground for the columns, just outside the edge of the floor to avoid breaking the rubble. The foot of each bamboo was wrapped in plastic till atleast 2’ from the bottom. Concrete for the footings was mixed and poured, first till 4” from the bottom. The rest of the concrete was poured after placing the column. At the top of the concrete footing was shaped into a shallow dome to prevent water from accumulating at the bamboo foot.
Each beam of the structure was made into a composite of two parallel beams, further cross-braced between each pair of columns. All the members have been tied using coir ropes. Temporary scaffolding was made from spare bamboo members tied at 4’ from the ground.
In order to stabilize the entire structure against wind and uneven loading, 3 cross braces were tied across the three bays. Each cross brace consists of two beams tied diagonally. To create a member long enough to span diagonally (6m), two beams were tied using coir rope with an overlap of almost 1m. Further, the two cross braces were also tied at their junction using coir rope.
As the workshop construction continued, it was apparent that the 8 columns may not withstand the load of the beams, cross-braces, trusses and the roof. Two more columns were added at each corner, forming an L-shaped composite column. The three columns at each corner were braced laterally using short bamboo members with fish-mouth ends.
Once this structure was built, the bamboo trusses which were made beforehand on ground were raised and tied, forming the structure for a double sloping roof
The biggest task to be done for the workshop space was the trusses, both in terms of their design and structural stability.These were designed in such a way so as to attain a height of 2.1m above the clear height of 3m of the workshop space. There was a possibility of using this height as a storage space, if needed, keeping wood and similar materials off the ground. The trusses were constructed using bamboo and plywood. The rafters were made of bamboo, and the struts, of plywood. The tie beams and cross bracing is also done in bamboo. The entire structure has 2 trusses at the ends with intermediate plywood members (struts) and 3 triangular truss frames in between.
To make the trusses accurately, 1:1 elevation of the truss was drawn on the workshop floor with chalk and members were then placed on the same to obtain the correct angles and sizes of the members. Once all the members were placed in their respective positions, they were bolted together using steel bolts and nuts.
As soon as the trusses were ready, the next task was lifting them up manually to that height and, of course, we needed the help of our masons and carpenters in fixing them in place. It took around three weeks to pre fabricate the trusses and get the framework ready for thatch roof.
So far we’ve had crazy winds blowing and thunderstorms but the workshop still stands strong and mighty against all odds! Quite a lesson to learn for all of us…