Honeycomb Wall Module: Detailed manual
Bamboo stubs of different Ø dimensoin but with equal height, placed randomly on a board. Even split stubs work.
Bamboo stubs of the same length create an impact resistance wall.
Even broken stubs can be used if having the same length.
A wall panel 60 x 240 cm, is built flat on a bench, on top of a OSB board or similar. 60 cm is a common width for a module to be handled by two people without machinery. 240 cm is a common ceiling height, although a matter of personal choice. The wall thickness is also determined according to personal choice: 5, 7, 10, 15 cm… A final module weight of max 50-60 kg is practical for the wall assembly.
Bamboo stubs are cut according to the standard wall thickness chosen and almost randomly placed on top of the OSB. The number of stubs needed depends on the density desired: if placed side by side, the impact resistance becomes extremely high, whereas if this is less needed and the number of stubs reduced by 50%, the wall could still be strong enough. A practical evaluation of different stub densities is worthwhile for a large project to avoid waste of materials.
When positioning the stubs on the board, a 10 cm space is left on one of the long side edges of the module for a vertical loadbearing culm to be included later on. 3-4 stubs should line up next to this space for later fixing to the culm. Likewise, 2-3 stubs should line up on the upper and lower side ends for later fixtures to floor and ceiling.
On top of all the bamboo stubs now placed on the OSB, a fine meshed chicken net is stapled, with at least three staples on every stub. A completely flat galvanized plaster net mesh 20x20mm would facilitate this. (Although difficult to obtain in Brazil) The whole cluster of stubs can now be lifted off the OSB, flipped upside down and placed on the floor.
The board must now be equipped with lists (with a 1 x 3-4 cm section) fastened with screws along all the sides. Depending on the thickness of the board a 2 cm high edge running along all sides of the board will now form a pool to contain a liquid mortar mix. To achieve a smooth final surface of the wall, a plastic film is placed on the bottom of the pool also covering the edges.
The plaster mix should now be prepared with the volumetric proportions 1 cement to 3-4 sand. A small-scale sample for evaluation is worthwhile here. The sand must be sifted to avoid gravel size stones sticking out. When thoroughly mixed in a clean bucket, water can now be added, little by little, so as not to waste the plaster mix by too much water. If color pigmenting was planned, it should now have been added to the water so as to be blended into the plaster. The total volume of the plaster mix should be calculated as 60x240x1cm=14,400 cm3=14.4 liters, given the size of the wall module and the The plaster layer could be much thinner than 1 cm, maybe down to 0.6 cm, in which case the total volume is adjusted accordingly. Only trial and error can determine this parameter.
Make sure that the board is perfectly level so that the mix is spread with equal thickness all over. Vibration can facilitate this: A stick screwed to the plate of a grinding machine going back and forth, makes enough vibration of the OSB board and the plaster pool.
Honecomb wall panel cross-section with external ferro-cement skin protecting against rains, UV ( sun), fire hazards, mosquitos...
After 1-2 days the honey-comb module can be lifted and separated from the board-pool and the plastic film. The load bearing culm can now be fixed to the 3-4 stubs lined up as already described. Preferably this culm should be fixed at the center axis of the honeycomb wall module seen from above, in plan view A1.
For fixing the load bearing culm, locate the three stubs lined up and drill all the holes according to detail drawing A1 before fastening any screw.
The Ø10 mm holes are first drilled from the outside. Then, the Ø5 mm holes are drilled on the inner side positioned as if mirroring the first hole. To find this position an A4 paper can be wrapped around load bearing culm at the first Ø10 mm hole, the circumference measured and divided by 2. Finally, the Ø4 mm holes are drilled in the corresponding (receiving) stubs. In order to finalize everything 35x5 mm diameter screws with Ø7 mm large heads are fixed to a Philips screwdriver with masking tape. Then it is entered through the 10 mm and the 5 mm holes to finally drive the screws into the 4 mm holes in the stubs, here acting as nuts.
The bottom end of the honey-comb module should be fortified with 60 cm bamboo slats under both edges of the stubs, drilled and screwed as the standard procedure. See detail cross section A2. Between those two slats there will be a guide rail, which is also a slat but fixed to the floor. This guide rail runs along the entire floor side. This way the honeycomb module will fit snugly to the other adjacent modules.
The upper side of the same module should be fixed to a recomposed beam, 6-8 cm high running over the entire wall, maybe 4-5 meters long. This fixture could be just a 6 cm screw going through the beam and then entering the lined-up stubs. After initial markings by a few turns of the drilling machine, Ø4 mm bore holes in the stubs may be necessary to avoid splitting by the screws.
This recomposed top beam distributes the weight of the roof structure down to the load bearing culms in all the honeycomb modules.
If bamboo culms are cutLikewise, 2-3 stubs should line up on the upper and lower side ends for later fixtures to floor and ceiling.
