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Basements in small buildings such as single-family detached houses are rare in wet climates such as Great Britain and Ireland where flooding can be a problem, though they may be used on larger structures.
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However, basements are considered standard on all but the smallest new buildings in many places with temperate continental climates such as the American Midwest and the Canadian Prairies where a concrete foundation below the frost line is needed in any case, to prevent a building from shifting during the freeze-thaw cycle.
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: ~3 s9 V" l) I" j& L; s' TBasements are much easier to construct in areas with relatively soft soils, and may be foregone in places where the soil is too compact for easy excavation. Their use may be restricted in earthquake zones, because of the possibility of the upper floors collapsing into the basement; on the other hand, they may be required in tornado-prone areas as a shelter against violent winds. 8 K6 r3 U" Y3 X: R$ S: ?3 \
- m5 y7 z$ s7 B; HAdding a basement can also reduce heating and cooling costs as it is a form of earth sheltering, and a way to reduce a building's surface area-to-volume ratio. The housing density of an area may also influence whether or not a basement is considered necessary.3 y8 z5 R1 Y4 `/ Z8 ^
: g7 C _/ p: \ K$ O% SHistorically, basements have become much easier to build (in developed countries) since the industrialization of home building. Large powered excavation machines such as backhoes and front-end loaders have reduced the time and manpower needed to dig a basement dramatically as compared to digging by hand with a spade, although this method may still be used in the developing world.: M- S& b- }# |' b: h1 E
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楼主: 兔宝宝
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