Bamboo Roofing

Bamboo roofing uses the hollow, fast-growing stems (culms) of bamboo either as the roof covering itself or as the structural frame for another covering such as thatch, tiles or sheets. It is traditional in many parts of South and South-east Asia, East Asia and Latin America.

As a covering

The simplest bamboo covering uses culms split lengthways into half-round channels. One row is laid concave side up, running from ridge to eaves, and a second row is laid convex side up over the joints, in the same pan-and-cover principle as Roman or mission clay tiles. In the Philippines, halved bamboo sections used this way on the traditional bahay kubo house are called kalaka. The natural flexibility of bamboo can also give rooflines a gentle curve, a feature associated with some East and South-east Asian architecture.

As a structure

Bamboo poles are widely used as rafters, purlins and battens under palm, grass or metal coverings. Colombia is noted for advances in engineered structural bamboo, and bamboo frames are also common in Indonesia, Vietnam and Ecuador.

Durability

Durability is the main limitation. Untreated bamboo is attacked by beetles, termites and fungal rot, and its internal life is commonly given as only about 2-6 years, and less than a year when it is exposed to water. Because the culm walls are thin, even small amounts of decay greatly reduce strength.

Treatment and design

• Boron treatment, usually a mix of borax and boric acid, is the most common protection against insects. It does not protect against rot and leaches out when wet, so it must be combined with design that keeps the bamboo dry.
• Copper azole is an alternative, though less tested on bamboo and more hazardous to handle.
• Design measures include generous roof overhangs, drip details, raising the structure off the ground and protective coatings.
• Traditional soaking and smoking give only limited protection.

Harvesting

Culms mature over about 5-7 years. Practitioners generally prefer to harvest a few months before the wet season; harvest timing also depends on species.