Seismic-Resistant Housing in PakistanEdit profile
THE ISSUE On 8th October 2005, Northern Pakistan was devastated by a catastrophic earthquake. Over 73,000 people were killed and 3.3 million were left homeless. Even though the region is prone to seismic activity, the houses built and rebuilt after these events have generally contained too little earthquake resistance due to a lack of resources and information about how to build safely. Article 25 partnered with international NGO, Muslim Aid, to develop sustainable seismic resistant building designs and to oversee construction in Jareed in Northern Pakistan and Bagh in Kashmir – both extremely rural and mountainous regions. THE SOLUTION Design Two house designs were developed following feasibility research into: • Seismic mitigation measures. • Vernacular construction methods. • Family size and domestic requirements particular to the area. • Materials and skills available locally. • Logistical challenges such as transportation of materials to site. • Most cost effective construction techniques. Article 25 then produced a full package of drawings for 2 house types, including plans, sections, elevations and details. These drawings were submitted to NESPAK (National Engineering Services Pakistan Ltd) and ERRA (Earthquake Reconstruction & Rehabilitation Authority) for approval, and both house designs received official approval for construction in less than three months. CONSTRUCTION Construction Method The houses were designed as lightweight timber structures, with stone and mud infill and a corrugated metal sheet roof. Local vernacular known as Dhajji Da (patchwork of timber and stone) was adopted and improved with additional design knowledge used. The following characterised the construction approach: • The timber frame was constructed as a well-connected box with adequate bracing in all directions. • The use of numerous small section timber elements filled with stone provides both flexibility and stability during a future earthquake. • The panels were small and evenly sized. • The base plate and wall plate were continuous. • All timber was well protected from moisture, especially from the ground. • The timber was of good quality with joint connections. • Masonry infill was used to provide additional compressive strength. Article 25’s consultancy service included a comprehensive and detailed design. Local and international consultants provided input where required, and details were refined to optimise buildability and cost efficiency. 1:1 prototypes were then constructed by local carpenters in co-operation with UN-HABITAT to demonstrate key structural details. These prototypes and sketches were used on site to communicate the construction details to local labourers. As these elements could be easily understood they enabled rapid improvement of the skills within the community. Construction Management An Article 25 project manager was present for the first four months of the construction period to monitor work on site. This onsite supervision mitigated the risk of costly construction errors. Construction was undertaken by local contractors and local labourers, ensuring that the local economy would benefit greatly from the construction. Training the local workforce was a critical component of the project and this ensured that the community was left better able to rebuild themselves in the long run. Regular onsite monitoring and adaptation meant that we were able to reduce material cost overspends, for example by reducing the gauge of reinforcement bars from an expensive 8mm down to an ample 6mm, providing the required support but saving in transport and purchase cost of steel. This vital saving was redirected into a series of retaining walls which would otherwise have been unable to be built; these will be lifesavers in the future by preventing damaging landslides, commonplace in earthquake prone areas. Seismic Resistance Measures • Seismic bands tied the structure together. • Many small bracing members were used to spread seismic energy and reduce the risk of damage and collapse during an earthquake. • The construction details used were approved by ERRA and NESPAK. • Galvanised steel straps added strength at joints between timber members. • The foundation and plinth bands were reinforced to NESPAK approved standard. SUSTAINABILITY Local materials were used throughout the construction. The masonry infill utilised stone reclaimed from the devastated areas. This effectively reduced the cost of transport, usually a highly restrictive factor in the Himalaya region. Local labour was used throughout the construction. This created jobs within the community and supported the local economy, and also taught locals the appropriate building and reinforcement techniques needed to help themselves better in their future work. Article 25 also led participative workshops that enabled local people to take part in the rebuilding projects. This created durability in the project by empowering the local community to continue the reconstruction efforts long after Article 25’s departure. THE END RESULT We were able to maximise the number of homes that could be built and the social benefit of the programme, constructing 82 houses with areas ranging from 41m² up to 67m². The cost of Article 25’s involvement in a project benefiting nearly 1,000 people was between £5-£10 per beneficiary. This minimal cost enabled close attention to detail and the effective mobilisation of traditional, local building methods. Sustainability, in its broadest sense, is the capacity to endure. This project will endure; these vital homes will resisit future earthquakes, the local economy will grow and prosper through the jobs that have been created and the legacy will endure, as the community is empowered with the skills and knowledge to continue building sustainable homes long into the future.