Philippine Vernacular architecture - traditional post and lintel construction makes use of building materials that are abundant and immediately available. Local timber, bamboo, and even palm fronds. This helps create a light structure suitable for the tropics. Another concept often used is that of a central space around which a house might be arranged and subsequently be expanded. The roof is regarded as an element in Filipino architecture with a steep slope for easily shedding rain, or a means for storing rainwater. The steep slope also helps keep hot indoor air flow upwards to the top of the roof and away from living areas. Overhangs protect the windows from sunlight and rain. Elements of Spanish-Colonial and American forms of architecture are very often inspirations to the designs.