Vastu is a science of Time and Space, just as Jyotisa is also a science of Time. While the approach of Vastu Sastra is scientific, the goal is always spiritual. The Smrti texts and the Puranas extended the scope of Vastu to include not only residential buildings but all constructions for private and public utility. The Garuda-Purana, for instance, takes the word vastu in the sense of building houses, hamlets and mansions, formation of townships, lying out of parks and gardens, construction of commercial streets, forts, temples and monasteries.

The Arthasastra adds to this list the building of dams and digging of tanks. Both these sources include the land on which the buildings and gardens are raised in the definition of Vastu.

The references in the Puranas and in the texts like the Arthasastra and the Sukranlti suggest the existence of the art or the science of building houses, palaces, bridges, canals, forts, dams, tanks, roads and parks. This was known as Vastu-vidya or Vastu-karma or Vastu-sastra. Occasionally, this discipline was called just Vastu, as in the Garuda Purana. And, there are references to this art or science having been assiduously cultivated by a long line of wise sages and expert-engineers. The Matsya Purana, for instance, provides a long list of eighteen experts who handed down this art in a traditional manner. They are: Bhrigu, Atri, Vasistha, Visvakarma, Yama, Narada, Nagnajit, Visalaksa, Aniruddha, Sukra and Brihaspati. The text further says that Lord Vishnu in his first incarnation as Matsya delivered in brief this discipline to the first of mortals, Manu.

It may be noted that plans and measurements of buildings originated in the Sulba-sutras, which were supplementary treatises to the Kalpasutras. The Sulba-sutras pertain mainly to measurements and constructions of different kinds of altars. In the Vedic ideology, sacrificial altar is the representation in miniature of the entire universe; and is, therefore, extremely important. It must be properly planned, accurately measured and suitable located. Different sacrifices have their own appropriate altars.

Two very important aspects of Vastu Vidya are knowledge of the direction in which a building is oriented and also the determination of a direction which a building should face.

It remains to be mentioned that Vastu-vidya has not only a great antiquity but considerable literature. It is regrettable that despite a phenomenal increase of interest in Vastu of late, the study of the extant literature on the subject is sadly neglected, thus occasioning a rich harvest of charlatans. It is not often realized that Vastu-vidya is a comprehensive discipline, and all aspects thereof must be taken into account, before suggestions for Vastu alterations and planning are made. In fact Vastu is a collective expression.