Earthquake resistant design principles were applied to the design in order to reduce the level of damage the building sustains during an earthquake. The simplistic rectangular form of the building eliminates weak structural junctions, which will reduce the amount of localized failings to the structure during an earthquake.
By using reinforced raft foundations the building has a very strong base that spreads its load evenly on the ground and reduces differential settlement. The foundation can be used to level a sloping site and mitigate problems associated with unstable terrain and soil conditions, so can be applied in most contextual situations in Nepal and Tibet. A 200mm upstanding plinth also creates a strong connection between the foundations and the structural frame it supports.
Steel footings and steel threaded bar connect the frame to the foundations. Simple fixings have been designed to allow for the use of either timber or steel for the main structural frame. The decision on which material to use will be decided individually for each separate unit based on local availability of timber and the carpentry skill level of homeowners. If steel is deemed to be the more appropriate solution for a unit, prefabricated galvanised steel elements will be used, and produce an extremely easy to assemble modular structure when twinned with the open steel mesh for the walls. The additional benefits of using a steel frame is that it is lightweight, quick to assemble and inflammable.
All four elevations are braced in opposing horizontal directions between structural elements, using the same material as the main frame, with some working in compression and some in tension. These will allow the building to move relative to the ground during an earthquake to reduce damage.
The stone infill system that has been designed for Safe House uses natural building materials found locally to the site to construct stable, insulated walls. Open wire mesh is connected to the structural frame on both the interior and exterior and is lined with either bamboo or reed mats to contain loose infill material. Depending on local availability, either rubble or stone can be used to fill the space which contains all important bracing. Once plastered with cement stucco or an adobe finish the walls will be extremely strong and able to withstand lateral movements that are induced by earthquakes and strong winds. The climatic zones in Nepal vary greatly across the country, and the success of this wall system is that it can be adapted to suit all climates. For example; increasing the stone infill thickness, adding an additional insulative layer and leaving thermal mass exposed, the wall can be adapted to increase heat retention for higher altitude locations.
The mesh and rubble wall infill system is structurally sounder than stacked stone walls which are typically used in rural Nepal, and the addition of bamboo woven mats creates a cavity wall which has much better insulative qualities than a simple stone wall. This should mean that the family use less fuel to keep it warm, reducing cost and deforestation of nearby woodlands. This in turn reduces the chance of landslides and flooding.
Openings in these walls have been kept to a minimum, away from structural junctions and regularly spaced between framing elements to reduce structural weaknesses. Precedent studies of vernacular architecture in the region showed similarly sized windows as they allow natural lighting and ventilation, but prevent high levels of heat loss and gain. Safe House uses this theory and applies it in a way to make it safer, by including a frame and ensuring their proper placement.
A large number of small windows are used to reduce costs, increase natural light in turn reduce reliance on gas, electricity or candles. The small size also helps with reducing heat loss/gain inside and they can easily be filled in with insulative material at night.
The structure of the roof has been kept as lightweight as possible to reduce the amount of falling debris during an earthquake. To do this, PVC tension fabric panels have been specified as the roof cladding, and they are connected directly to the roof truss to ensure stability. By reducing the weight of the roof compared to a typically thatched roof used in the region, the centre of gravity is lowered. A low centre of gravity prevents high level movement during an earthquake and puts less strain on the structure. This material is cheap, easily available and waterproof, allowing the large area of the roof to harvest rainwater, which collects into storage tanks via the gutter.
The construction timeline for the building is estimated to very short, taking people from temporary accommodation to a permanent dwelling within one week. As many of the materials and labour are sourced locally from the recipients of the house the timeline and cost of the building is kept to a minimum.
The modular nature of Safe House allows the internal organisation to be changed depending on the needs of recipients. In our proposal we show two options; a semi-detached two unit option for two families, and a single unit option for a larger family with two bedrooms. Both options are able to accommodate between 6-8 people comfortably.
Internal spaces have kept a very simple design to allow to most flexibility of the space. As many Nepalese people still use firewood as their main fuel for cooking, the only fixed element within the space will be the stove. This will be located beneath an opening to ensure that the space is well ventilated and homeowners’ health will not be affected by breathing in smoke. The remaining space within each unit can be organised and tailored by families to suit their specific needs, as we know that any home design needs to have opportunities for customisation. An additional benefit of creating simplistic internal spaces is that the use of the building can change over time as families construct their own, more permanent, dwellings and move out. Potential future uses for Safe House could include; classrooms, health clinics, community centres or tourism infrastructure.
To accommodate a toilet into the design, and to keep the internal spaces free, a separate toilet block has been designed to be located close by the building. Placing the toilet outside of the main building has a number of benefits. It allows the internal living space to be organised for either one large family or two smaller families without having to build two toilets as it can be communal. It will be more sanitary as it allows for more appropriate placement in regards to sewage treatment and removal. As many Nepalese do not have access to a toilet the addition of one within the main living space may not be appreciated.
Safe House is not only modular within its’ structural elements, but also within its entirety. In our proposal we outline a number of different layout options. By placing two Safe Houses next to one another materials, labour and costs are reduced as external walls can be shared between two units. Depending on the external wall they share a range of different layouts can be achieved, including; a row, a courtyard and a back-to-back block, as well as detached and single unit options.