The main residence concept was inspired by the panoramic views. The changes of level followed the natural terrain on the ridge. The owner wanted an open plan naturally ventilating building with the lowest possible power demand. With only monkeys birds and butterflies for neighbours I did the maths and realised that fixed glass was the lowest cost wall long term. At 220m elevation the ambient temperature ranges between 20 & 32 deg C so wall insulation was not needed. Living in tropical Padang is different to Bali. I knew the house needed to work well in rain storms so I opted for a lot of glass louvres. Fully insect screened living spaces are essential in the jungle or the jungle will come to visit when the lights go on at night. Most of all the owner wanted panoramic views from every part of the house. MATERIALS
Material choice was easy. The rocks are from the site and the surrounding hillsides. The friends and families of the tradesmen stacked them in carefully measured piles and a beat up old truck collected them every week. Padang has one of the oldest cement factories in the world and the product is export quality so concrete floors and a structural frame were something that the local masons were skilled at building. The timber for the roof and suspended floors was easy to find and the plywood ceilings came from a local factory. Glass, aluminium and steel all came from Jakarta or Medan but nothing in the structure need to be imported. The owner wanted marble floors from the outset and was lucky enough to find a supply of export quality very hard marble (almost a granite) in a pale grey colour that worked very well with the local stone. Black marble for the bathroom came from Solok in the mountains and the same quarry offered us free off-white marble quarry scraps… these now cover all the terraces. SITE
There were no trees in the footprint… some past owner had cleared the area for growing chilli. The ridge lies on solid rock (I surveyed the area with care) and is well drained and stable. Next came an A3 pencil sketch of the plan and elevations and I went to site to see how well it fit. After some quick measurements, the owner started splitting bamboo with a machete and staking out the perimeter of the building. We set up some bamboo frames to check floor levels for the cut and fill and played with the curve by eye until it felt right… DOCUMENTATION
I thought, ok thats good, now I can start the architectural drawings… then the owner said: “you’re far to busy to do the drawings so lets start digging the foundations now” …. as an architect, I was astounded of course! We always do drawings in great detail, get engineers to do more drawings, change the design several times and finally call contractors to quote on the documents. The owner was having none of that. I told the tradesman who had built the garage retaining wall to start digging the footings that afternoon. They dug down to rock and I told them how to place the steel in the trenches. Within a week we had the stone walls started but still no idea how we would build the roof. Not even the beginning of an idea. Back at the hotel the owner started playing with cardboard inspired by the way a pack of cards splays to make a stepping curve. I found that we could generate triangular sections of roof that stepped down if I worked from the focal point of the curved walls and the idea of the radiating roof beams came naturally. I calculated that these roof segments could each be perfectly level and step down to the next by sitting on top of it. 3D MODELLING
Knowing the area was prone to earthquakes, I had conceptualised the structure as a series of reinforced concrete ring beams about one meter apart in the vertical plane. This was in part inspired by traditional Nias oval houses we had seen in books and in part by the radical floor plan. Oval or round buildings resist earthquakes by moving in the horizontal plane “as one” rather than concentrating seismic forces that destroy rectangular structures. The idea was to avoid any hard corners in the multi story section of the building where there was far more glass than stone wall. The only right angle corner in the entire external wall is in the South East corner. At that point the building sits in a excavated terrace well below natural ground and directly on bedrock. The stacked ring beam concept freed us to place walls and columns where we wanted as we built the stonework. The rings were also placed at every floor level and tied into the floor slab with a lot of reinforcing bar.
- The other way this building handles quakes came about by chance. The owner needed to store a lot of rainwater because there is no mains supply anywhere near us. There is no ground water either because we are located on a saddle at the top of a mountain. I designed large tanks under the floor to store water. Later I found out by direct observation that the big water tank under the house (and the one under the studio) act as shock absorbers in a quake. They are very effective dampers. A graphic example of this is the hand blown glass vase that you may have noticed in photos of the lounge. It is heavy and has a spherical base and a very long neck. It is generally filled with water and a bunch of leafy whatever from the garden. It is not what you would call stable having only a small flat base.
- In the big quake the vase rocked but did not fall down. A lot of more stable looking items like clay planter pots fell and broke. I am convinced that the water sloshing in the bowl stabilised the vase…… and that the water in the subfloor tanks saved the buildings from cracking.
ROOF Next came the steel pipe “hub” for the spiral roof and a local welder make ring brackets that were a good fit but free to slide and turn. After building scaffold to support the hub and the workers joined the roof beams to each bracket. Using lots of bamboo supports they then moved the beams radially until they created the column and wall configuration I wanted. The beams were then jacked up one by one so that bottom of each beam was level with the top of the beam below. As each beam was located, we added more bracing and props to keep in place then dropped lead lines to determine the placement of the starter bars in the ring beams… then the walls were built and columns poured up to meet the beams… the opposite way to conventional construction but very fast and accurate. I doubt we could have done it any other way!
DESIGN AS YOU BUILD Many architect friends have visited Air Manis Hill Residence and all of them find it hard to believe that this structure was built without a single measured drawing…. the process was more like sculpture than architecture and a very liberating experience for all involved. I would never have tried had the owner not started digging the foundations the day after the pencil sketch. It was the most exciting build of my life and totally hands-on…. as they say on Myth Busters…. don’t try this at home!