It’s all about imaginative placing
May be the act of designing is all about exploring and discovering the hidden potential. Perforated filler roofs fit perfectly into this theory.
The design profession is strange. Often it does not take a project context as a mere fact, but loves to fantasise it. Designers play around the building form and attempt different combinations only to explore the options available, where some good options actually never get built!
Instead of using materials in their basic and simplest form, people try exploring the myriad ways of using them to get a variety of effects from the very same stuff. May be the act of designing is all about exploring and discovering the hidden potential.
Perforated roofs are a perfect fit to the above story line. As the sun moves across the sky, the sun’s rays move across the room, as if the roof acts like a cloak.
This idea started with architects placing coloured waste glass bottles within the roofs, randomly or in a design, creating a picturesque interior. Despite the attraction, issues such as water leakage, breaking of bottles, and shifting during concreting halted the popularity of this idea.
Jaali roofs on steel frames are an extended version and comparable beauty to watch, but appear weak in areas of high security threats.
Replacing steel frame by RCC and embedding the jaali blocks into the slab gives us the normal secure concrete roof, but with the playful small void, each acting like a small pinhole camera.
Adhere well with concrete
The half-cut hollow clay blocks are by far the easiest materials to embed in the roof, though other locally available options could also be employed. Reinforcement rods are placed as per structural design, which should be based on the block sizes. Upon the normal shuttering, hollow blocks are placed with holes up facing skywards with reinforcement rods in between to get the chosen design format.
Structurally, this system acts like a filler slab; hence the blocks adhere very well with concrete, avoiding water seepage possibilities. These blocks can be patterned on any geometry, as long as the steel rods are in position as desired. The normal concreting is preferred more than the ready mix, to ensure the holes are kept clean.
Placing a piece of glass on top ensures rain protection.
Also as skylights
The perforated roofs also act like skylights, though with much lesser direct light.
In hot dry regions where light comes with high glare and sky brightness, it is climatically difficult to have large clear glass skylights, hence this design idea with small holes becomes a good fit that filters in soft light.
Incidentally, in hot regions such as Rajasthan, even the large window openings are replaced by jaalis of small voids!
The challenge is to increase the daylight factor, without increasing glare and sharp shadows. However, there would be increased indoor heat gain; hence roof bottom ventilation is a necessary provision.
The perforated RCC roof does not become lighter than the normal filler roofs, but visually appears lighter.
Besides the eco and aesthetic benefits, the major attraction for perforated roofs could be that it’s a do-able alternative idea, which demands no extra construction skills.