Two-Tiered Tumpang Pyramidal Roof Timber Framing in Balinese Wantilans

In the sacred landscape of Balinese Hinduism, the skyline of every temple complex (pura) and civic center is punctuated by towering, multi-tiered thatched roofs known as meru and tumpang. In sacred architecture, the number of tiers (which is always an uneven number—3, 5, 7, 9, or 11—for temple shrines) symbolizes the stepped ascension through the heavenly realms toward the summit of Mount Meru, the cosmic axis of the universe. In the civic architecture of the wantilan, master builders translated this sacred verticality into a pragmatic two-tiered (tumpang dua) or three-tiered (tumpang telu) pyramidal hipped roof.

This stepped geometry was an architectural necessity for public assembly halls. Spanning a cavernous open pavilion measuring twenty to thirty meters across with a single continuous pitched roof would produce an unmanageable, colossal structure with towering gable walls vulnerable to hurricane-force equatorial wind gusts. By fragmenting the monumental roof envelope into overlapping, telescoping pyramidal tiers, the master builder reduced the individual rafter lengths, lowered the center of aerodynamic drag, and created an imposing, floating architectural crown that visually anchored the village public realm.

The structural choreography of a two-tiered wantilan roof begins with the four central pillars, known as the saka guru. Sized with massive diameters of 30 to 45 centimeters, these primary columns demarcate the central sacred quadrant of the pavilion. At their upper terminus, the posts are joined by a heavy rectangular timber ring beam assembly called the lambang sari. The beams are joined to the columns using complex through-mortise connections, secured with wedged timber keys that pull the four columns into an ultra-rigid, self-bracing space frame.

Resting directly atop the lambang sari is the secondary timber structure that supports the upper roof tier. Short vertical king posts (saka tumpang) rise from the ring beams, carrying the upper collar ties and hip rafters that form the apex pyramid. Radiating outward from the base of the lambang sari, a secondary network of massive diagonal hip rafters descends at a shallower angle to meet the outer ring of perimeter columns. This clever structural redistribution ensures that the tremendous dead load of the upper tier is transferred straight down through the stout central saka guru columns, leaving the perimeter columns lightly loaded and permitting the outer perimeter to remain completely wall-free.

The layout of the radial rafter network (iga-iga and usuk) showcases the geometric mastery of the traditional Balinese carpenter (undagi). Because the roof is a four-sided pyramidal hip, the rafters do not lie in a simple parallel plane; instead, they converge from the rectangular perimeter toward the diagonal hip rafters and central ridge beams. Each rafter end must be hand-cut with a compound-angled bird's-mouth notch that beds perfectly over the curved timber wallplates without slipping.

Rather than using heavy sawn lumber for secondary roof battens, Balinese builders employ indigenous giant bamboo (Gigantochloa apus, known locally as tiing tali). Mature bamboo culms are harvested during the waning moon when sap levels are lowest to deter powder-post beetles, split lengthwise into flexible strips (reng), and soaked in flowing river water to leach out starches. These bamboo battens are lashed horizontally across the rafters at tight 100 mm intervals using wild split rattan cordage (tali rotan). This creates an exceptionally lightweight, springy, and flexible underlayment grid that moves harmoniously with the timber frame during wind storms without splitting or loosening.

While modest agricultural pavilions across Bali are thatched with common alang-alang grass, the monumental roof of a grand wantilan is clad exclusively in duk (or ijuk)—the coarse, jet-black natural fiber harvested from the trunk of the sugar palm (Arenga pinnata). As the sugar palm grows, its trunk naturally produces dense mats of thick, wire-like black fibers that protect the tree from torrential rains and tropical insects. When harvested, combed, and tied into thick bundles, duk represents one of the world's most durable natural roofing materials.

The thatching process is an intensive community ritual. Thousands of duk bundles are stitched to the bamboo battens starting from the eaves and progressing upward in overlapping courses, achieving a final thatch thickness of 150 to 250 millimeters. This dense, fibrous black thatch possesses remarkable architectural properties: it is completely waterproof, highly resistant to UV degradation and fungal decay, and provides supreme thermal insulation, keeping the pavilion interior ten to fifteen degrees cooler than the tropical ambient sun. Furthermore, during deafening equatorial downpours, the soft fiber matrix absorbs the acoustic energy of falling rain, allowing civic debates, gamelan performances, and community assemblies to continue in clear, peaceful acoustic comfort.