The roof is made of sloping palm trusses. Palm wood is used because it is locally available. On comparison, the density of 1 sqm of teak is 900 kg/m3 and the density of 1 sqm of Palmyra is 970 kg/m3. The high density of palm also makes it difficult for termites to chew through. Palmyra wood does not get infected by termites as soon as other woods do.

The treatment:

The middle portion of the Palmyra is a bit soft and is prone to termite infection. Thus only the outer part of the palm is used for trusses. In order to prevent the infection three coats of cashew nut oil is applied.

The design:

The roof was designed to exchange hot air effectively. The sloping roof attic is concieved as a hot box with false ceiling with holes. The air in the attic gets heated and thus creates a low pressure area. As the air below the false ceiling is cooler a pressure diffrence is created as a result of which air from lower floors move up towards the hot box through the holes in the false ceiling. The roof was designed in a manner that this rapid air exchange could happen.

The roof truss implemented is a couple-closed roof system where in notches provided at the feet of the rafters prevent them from spreading. If the span of the roof is increased or the loading on the truss is increased gradually, it will be found that at a certain stage the notch will be incapable of resisting the thrust at the end of the rafters and the roof will collapse. Thus, to prevent this, the feet of the rafters are joined by a tie, which by holding them in position, prevents them from spreading and thrusting out of the wall.

The roof trusses rest on a palm wooden runner beam that rests on the wall. The rafters sit on this beam.

The rafters are held by a tie beam (couple-closed roof truss).

For ventilation the top is left open and an additional truss system is laid on the couple-closed truss system.

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