Give examples to illustrate what factors restrict the folk customs of life.

Folk custom of folk houses is restricted by many factors, including natural factors and humanistic factors.

First of all, natural factors are the basis for the formation and development of folk customs. For example, caves in the Loess Plateau are formed due to local natural conditions such as thick loess soil layer, developed vertical joints and less precipitation. Some areas with abundant precipitation in the south, such as Guangxi and Guizhou, have lush vegetation and a wide variety of organisms. This way of living can be ventilated and moistureproof, and it can also prevent poisonous snakes and beasts.

Secondly, humanistic customs are also an important factor in the formation and development of folk customs. For example, in China, due to the philosophy of "the unity of heaven and man", geomantic omen plays an important role in folk customs. People will choose the location and orientation of building according to geomantic omen, so as to obtain the best living environment and fortune. In addition, the cultural background and socio-economic conditions of different regions and nationalities will also affect the formation and development of folk customs.

Finally, the national ethnic policy will also have an impact on folk customs. For example, China's policy of regional ethnic autonomy encourages all ethnic groups to carry out modernization on the basis of maintaining traditional culture, which also has an impact on the development of residential folk customs.

To sum up, the formation and development of folk customs of residential houses are restricted by many factors, such as natural factors, humanistic customs, national ethnic policies and so on.