gravel to allow a half-width RC ring beam under the wide walls. Forming the house A roof can be formed by gradually sloping the walls inward to construct a dome. Vaulted roofs can be built on forms. Or a bond beam is used under a traditional roof type. Hip roofs, gable-type trusses or vigas may be needed to reduce outward stress on earthen walls. Earth domes are inexpensive to build, but waterproofing them is complex or expensive in humid regions. Windows and doors can be formed with a traditional masonry lintel or with corbeling or brick-arch techniques, on temporary forms. Light may also be brought in by skylights, glass-capped pipes, or bottles placed between bag courses during construction. Finishing Cover the wall to prevent damage to the bags from UV rays or moisture with cement-based stucco, or lime or earthen plaster. If walls are 'raw' earth, an infill plaster of earth with straw is used to fill the nooks between bags or courses. A finish plaster is applied on top. Roof overhangs are helpful to reduce plaster waterproofing requirements, although plaster on lower walls may be stronger and more water-resistant than plaster on upper walls. Some buildings use a planted-earth "living roof" ("green-roof") to top the structure, while others use a more conventional framing and roof placed atop earth-bag walls. Environmental friendliness Earthbag construction uses very little energy compared to other durable construction methods. Unlike concrete, brick or wood, no energy is needed to produce the earthen fill other than gathering soil. If on-site soil is used, little energy is needed for transportation. Unlike rammed earth construction, only human labor energy is required to tamp the soil lightly. The energy-intensive materials that used – plastic (for bags & twine), steel wire, and perhaps the outer shell of plaster or stucco – are used in relatively small quantities compared to other types of construction, often totaling less than 5% of the building materials. Buildings last a long time when maintained. However, if "raw" or unstabilized soil is used as fill, when the building is no longer useful the earthen fill can be recycled into either garden areas, backfill, or new earthen buildings. Use in disaster areas Earthbag building techniques were also explored in Sri Lanka after the 2004 tsunami. Multiple earthbag construction projects have been completed in Haiti, most of these after the earthquake. First Steps Himalaya and other charities had