It is very essential to determine the directions correctly. In absence of the correct demarcation of directions, positions of various rooms, and doors etc. will be faulty which will change the whole situation of the house. It may turn into situation against the principles of Vastu Shastra rendering the house inauspicious. Necessity of correct marketing of directions is also expressed in our scriptures:

Prasade Sadane alinde dware kunde visheshtah;

Dik moodhe kulnashah syatasmatsa shodhay eddishah.

i.e.; It is necessary to determine the directions correctly while constructing a temple, palace, house, gates, porch, pond etc. in proper direction.

Therefore as per instructions of Vaastu Shastra, a building construction should be started only after marking of the directions, east-west etc.

In ancient scriptures, methods  for determining the directions with the help of the shadow formed when a cone is placed in sun on the open plot, or by observing the pole-star or other constellations in the night.

Now a days, directions can easily be marked by the architects with the help of the compass. Direction and position of a room or gate etc. can be correctly decided only when the construction work is started after marking the directions properly. It can be noted that several magnificent buildings built without proper consideration of direction are being rectified under the expert guidance of learned architects and scholars or Vaastu Shastra. Therefore it is better to start the work after determining the directions so that the building is constructed according verandahs (balconies) and also the rooms are constructed in proper place and in proper direction, there remains no defect in the building, and inmates are blessed with all the happiness and good fortune.

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Just as it is necessary to think over the merits and demerits of the plot of land as mentioned in Vaastu Shastra, one has to be much more cautions in the construction of the building. A building constructed according to the basic principles given in Vaastu Shastra keeps the inmates happy and prosperous. In modern sense, to make the five basic materials, viz; earth, water, fire, air and space, fovourable to the house is the very essence of Vaastu Shastra. Therefore while constructing a house, rules or principles given in Vaastu Shastra regarding direction, shape, level should be taken into consideration. For example, south-east corner is the seat of the god of fire, Agnidev. So kitchen and any room for works related to fire/heat should be made in this corner, then only the house will be trouble free. Constructions against the laws of nature at one's own will may cause pollution, which gives rise to many other problems of health, fear etc. that will result in loss of wealth, property and life also.

Directions have very much significance in the construction of a building. The four directions have their own importance, where as the corners formed by the concurrence of two direction are much more important because effects of both the directions can be felt at the corners. The gods governing these directions are noted below:-

Directions                                 Name of God                              Effect
East                                          Indra                                        Progress&growth
South-East                                 Agni                                         Energy,Strenght&vigour
South                                        Yama                                       Death
South-West                                Nairut                                      Purity&Cleanliness
West                                         Varun                                       Water
North-West                                Vayu                                        Air\Winds
North                                       Kuber                                       Wealth\Prosperity
Vertically above                         Brahma                                    Spiritual knowledge
Below                                        Anant                                       Resurces,Worldly pleasures

These gods govern the directions and control the various areas as given above. For successful implementation of any plan, the concerned god is worshipped. Room or space in a particular direction should be used for a purpose suitable to the nature of the god and the material he controls in that area. That is how to avoid defects of Vaastu. The god controlling the area in the house is worshipped and offers made to please him, requesting for his blessings and peaceful happy life.