MADRAS TERRACE ROOF

This system involves masonry brickwork supported on closely spaced rafters. Thin bricks (or bricks laid on edge) are held together by lime mortar on timber rafters. The top layer of bricks is laid flat over the bottom layer, and is then topped by a layer of lime surkhi (lime concrete). The rafters usually rest on the load-bearing walls. This flat terrace method of roofing has been used in the gopura to form intermediate floors at the five stepped levels. As many as six layers of brick form part of the Madras terraces here 

CONSTRUCTION
Wooden beams, normally teak wood, are be first placed upon opposite walls across the width of the room, 18 to 24 inches apart.

High density clay bricks called Achikal, made to special thin size measuring 1”x3”x6”are used. Well matured lime mortar is used for bonding the bricks that are placed at an angle of 45 degrees to the wall, or diagonally across the room width.

These bricks, placed on the edge, ensure tensile strength.

The roof is cured for a minimum of one week and then a three-inch thick layer of a mixture of five parts of lime mortar, three parts brick, one part gravel and one part sand. This layer provides the compressive strength and load bearing capacity to the roof. This layer is well compacted, cured and levelled. The final layer would depend upon the slab being an intermediate one or the final roof. If intermediate, a floor finish like red oxide or lime mortar would be applied and if final, there would be courses of flat weather-proof tiles topped by thick mortar to slope. 

MATERIALS
Madras Terrace Roofing, being a vernacular architectural practice, native/local ingredients were used.

1. ‘Achikal’ Bricks
   High density and high strength clay bricks, made to special thin size measuring 1”x3”x6”.

2. Lime mortar

3. Wooden rafters

4. Brick Jelly

5. Lime Concrete
   Lime concrete is a composite mixture of lime as binding material, sand as fine aggregate, and gravel as coarse aggregate in appropriate proportions. Lime concrete mix ratio depends on the type of construction, but in general, it can be taken up to a 1:2:3 ratio for lime, sand, and coarse aggregate, respectively.

6. ‘Kaduka’ Fruit/Jaggery
   For 1000 sq. ft, 60g of Kaduka fruit (without seed) will be used.
   Jaggery is also used along with that, and they will be kept in a tank for 15 days for fermentation.

ADVANTAGES

• Madras terrace roofs have an astounding lifespan of about 150 to 200 years, much higher than the RCC slabs.

• Since a good amount of locally sourced materials are used, and the requirement of materials used for construction is less, the expenses for incurring and transporting the materials are less.

• The materials used provide a natural coolness to the place and reduce the temperature more than RCC slabs.

DISADVANTAGES

Debris and water must regularly be removed from the floor to avoid collapse and leaks.

• Laying of such traditional roofing requires skilled professionals.

• They are fairly heavy and so decent supporting rafters are required.