Crafting Metal Roofs

With R Ravindrakumar & Suhasini Ayer, Auroville

In a world of tremendously paced technological advancements, technique often supersedes skill as technology replaces craft. While alternate modes of construction and production with higher efficiency and precision levels continue to influence the building industry, there exists a sustained effort to renew processes rooted in intuition and the idea of endurance. Suhasini Ayer, Principal Architect, Auroville Design Consultants and R Ravindrakumar, Principal, Ravindrakumar Roofing Technology, shed light on aspects of sustainability and construction methodology deployed in crafting the metal, respectively.

The term ‘sustainable’ building materials often gets used synonymously for low embodied energy and low carbon building materials. As a high embodied energy material, metal as a choice for roofing may seem like a rather counter intuitive choice for professionals especially seeking to build sustainably. All roofs are required to be resilient to the contextual weather conditions, to the geophysical, temporal and functional stress besides sheltering the building it sits on.

In areas of difficult soil conditions and zones with seismic activities, the low self-weight of metal roofs allows the foundations and framing structures to be considerably lighter when compared to the conventional RCC slabs and compression structures such as brick domes and vaults. This goes a long way in lowering the quantity of material required for foundations and superstructure, thus the overall cost of the buildings.

Metal roofs have reflective factors of 65% or more, reducing the heat gain in the building considerably and have emissivity ratings of .85 or greater, allowing the stored heat to be re-radiated up and away from their surfaces, rather than harboured and absorbed by the rest of the structure. This is desirable in lowering the heat island effect, lowering the cooling demand. In terms of resilience and longevity of metal roofs, if implemented with a skilled team- these roofs are good for five decades or more if there is no damage due to unforeseen factors.

Magnificent Copper Roofscape at the Kaviyoor Temple in Kerala [Cosmic Dance in Stone by Ramu Katakam, 2017]

The steep copper roof at Koodalmanikyam Koothambalam at Irinjalakuda, Kerala [Cosmic Dance in Stone by Ramu Katakam, 2017]

Historically, metal has been used for roofing for 2500 or more years, either as sheets or shingles of copper and alloys of copper, iron or steel coated with zinc and in aluminium since the 20th century. In Auroville, some of us have been designing and building aluminium (corrugated and non-corrugated sheets) roofing since the late 90s as we had a highly skilled resident metal roof craftsperson who trained a handful of local metal fabricators of grills and gates. The more enterprising of them have now branched out and undertake contracts for metal roofing in peninsular India, appreciated for their high quality of workmanship.

The design of the roof shape combines various aspects like the structure, function of the building, economy and timeline along with ascetics of form and proportion. As the heat transfer is high during the day, it is desirable to have good insulation that is adapted with the false ceiling. This also helps with the noise of the rain that can be quite deafening otherwise. In some parts of the world the metal roof is disconnected from the insulation by a maintaining a gap of 4-6 inches allowing for air flow as heat exchange. The anodized sheet develops a weathered patina within one seasonal cycle, making it less reflective to prevent reflected glare to the surrounding, and retaining enough reflectivity to prevent heat gain.

Metal roof edge detail

View from inside the Auroville Public Library; Auroville Design Consultants

View from outside the Auroville Public Library; Auroville Design Consultants

Auroville being in a hot humid zone, any spaces are avoided between the metal roof and the insulation to prevent condensation of the trapped air. Humidity in non-accessible areas poses a risk for fungal infestation, besides providing a protected habitat for the considerable biodiversity of insects in the tropics- where no amount of insect proofing works, and life always finds a way!

Crafting Metal Roofs

In a recent visit to Auroville in Tamil Nadu, [IN]SIDE documented the fundamental steps involved in the construction and laying of a metal roof, as demonstrated by R Ravindrakumar and his team.

Kumar was introduced to the craft by a Frenchman more than a decade ago and ever since, he has been experimenting independently as well as working on several projects alongside architects. Today, he has a team of 15-20 people, all of whom are trained in the various stages involved in the process of construction.

The possibilities of metal roofs are many – aluminium, steel, and zinc- apart from copper, and each of these possess innately different properties. Based on their characteristic tensile strengths, the metals are normally rolled out into sheets for roofing and cladding purposes. Copper, being compatible with all kinds of metals is also used as an alloy in the form of a mix of other metals including bronze, brass, tin, zinc, and aluminium.

Although naturally resistant and not prone to decay, the workability of the metal for construction is not so simple to handle. Therefore, the importance of a skilled hand is critical to the construction- keeping a check on commonly encountered problems such as penetration of the metal surface, erosion of the metal, loose seams and flashings.

A well-fabricated metal roof can prove to be economical and a long-term solution- it is low-maintenance, requiring no painting or finishing and all of the metal is recyclable. The proposed structure of the roof is the pivotal starting point- the sheet size and the spanning between purlins is based on this. Metal Roofs, believes Kumar, unlike the conventional tile-roofing systems have the advantage of ease of customisation. They can be used as a sheeting in any odd corner of a building. Additionally, the sheet is recyclable as a material and the upkeep is minimal if assembled and insulated well enough.

First, on a metal under-structure of trusses, beams and purlins, the false ceiling is fixed

The edge sheet is held in place to anchor the gutter eventually

The edges are chamfered for a clean fold

The metal sheet for roofing is then cut to size

Using a special machine fabricated in Auroville, the metal sheets are folded into troughs

With self-fabricated “V” clamps the adjoining lip of the troughs is then crimped and twice folded, making the joint water-proof

Depending on the aesthetics, this fold is either left as is or could be batted down

The insulation is laid out to receive the metal sheets when using non-corrugated aluminium sheets

The metal sheet is folded twice, forming a trough-like formwork between the spacing

Anchoring the gutter section to the edge profile with brackets

The intent of ‘making’ evidently comes alive in the pursuit of a craft. The distinction between technique and skill is an important one to make when assessing the efficiency of employing ‘craft’ in architecture- while former trains in the ability to perform, the latter is critical to the quality of execution. In a land, as culturally diverse as India there exists a plethora of such distinct skill-sets that are refined over time and diligently passed on as a discipline. It is important to establish here that the idea of craft is not so much about a nostalgic connection to a tradition but what it ‘affords’. Endurance is at the core of most craft-based practices while their ability to constantly renew with time is embedded in the innate motivation to ‘make’.

Beyond the banal understanding of a ‘cause & effect’ idea of craftsmanship, there is a deep sense of affection associated with this art of manipulation- in the doing and undoing, the haste and slowness, even in the accuracy and inaccuracy. Today, several contemporary architecture practices have rediscovered the potential in the embodiment of craftsmanship- the idea of contamination of space with human touch. And it is here that architecture and the crafts find a common ground as a practice in the way it is understood as an extension of the body in the inhabited atmosphere and all that it encompasses- this is what ties us ♦

SUHASINI AYER is a graduate of ‘Delhi School of Planning and Architecture’; living in Auroville since 1985 and one of the co-founders of the Auroville Centre for Scientific Research; an organisation dedicated to research and experimentation in the field of appropriate building materials and technologies, water management, renewable energy and solar passive/ climatic architecture and sustainable urban planning.

As head of the Auroville Design Consultants, the Planning and Design wing of this organization, she has designed and implemented over 50+ projects in India in the last 25+ years. She was co-recipient of the Hassan Fathy Award for ‘Architecture for the Poor’ in 1992, co-nominated for the Aga Khan in 1992 and recipient of the Design Share Award for educational buildings in 2003 and 2005.

R RAVINDRAKUMAR is based out of Auroville, Tamil Nadu and has closely collaborated with several renowned architecture firms based out of Auroville over the years. He is the Principal and Founder of Ravindrakumar Roofing Technology that is actively engaged in training youth in the construction of metal roofs and successfully completing commissioned projects independently.

For any further queries on Metal Roofs, connect with R Ravindrakumar at +91 97867 23129