Nowadays, when we imagine enclosed spaces, concrete slab roofs often come to mind. However, the use of concrete in construction now raises concerns due to its documented contributions to climate change and environmental harm. In response, it is necessary to incorporate vernacular and traditional techniques into our architectural toolkit. In this context, natural coverings emerge as an excellent solution. Despite their alignment with numerous desirable project attributes, these materials, which have sheltered humans for centuries, are still underutilized in contemporary construction. Natural roofs offer biodegradable materials, making them a more sustainable option with an aesthetic appeal and enhanced thermal comfort.
One of the most common natural coverings is thatch, a traditional method that utilizes dried vegetation such as piassava, sape, and santa-fé grass (Panicum prionitis) to create sheltered structures. Thatch assembly typically starts from the bottom and progresses upward, with special attention needed at the top due to its vulnerability to water infiltration during both construction and future maintenance. The steepness of the roof slope plays a crucial role in preventing potential leakage issues, as it facilitates faster water drainage. Thatch coverings are typically installed on wooden or bamboo frameworks, and their flexibility allows architects to explore creative possibilities, including complex organic shapes.
When adopting this solution, it is worth paying attention to the different types of thatch available in the market to decide which one should be used in your project. As mentioned earlier, the most common ones are:
- Piassava: Due to its superior flexibility, piassava has the finest fibers, causing its ends to drape over the roof's edges. Depending on factors such as maintenance and local conditions, piassava coverings can have an average durability of around 8 years;
- Thatch: Unlike piassava, it has a more rigid appearance and lends itself to finishing coverings with straight lines. However, it typically has a shorter lifespan, lasting approximately 5 years;
- Santa-fé Grass: Among these materials, it is the most rigid, displaying a solid block-like appearance. Thanks to its exceptional durability and robustness, it can endure for roughly 20 years, making it a highly versatile option for various construction applications.
All these materials are highly flammable and require fire protection treatment. It's also crucial to verify the material's source for trustworthiness and ensure that purchased materials are free from pests that could harm both the covering and the building. Besides the significant sustainability factor, this solution offers benefits such as excellent thermal insulation and aesthetic qualities that foster a continuous connection with nature.
Another significant choice for natural coverings, while less common in tropical regions, has a strong presence in vernacular constructions worldwide: seaweed. Designer Kathryn Larsen has demonstrated their resistance to decay and fire, their absence of toxic elements, and their insulation properties that rival those of mineral wool.
