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Low-Cost, Long-Span Fire-Resistant Wood Construction Technology: O・Mega Wood (FR)

In technical cooperation with Shelter Co, Ltd. (http://www.shelter.jp/en/about-en/company-en), Obayashi Corporation has developed O・Mega Wood (FR), a wood construction technology that allows the construction of fire-resistant long-span frames at low cost.

Using timber in construction has been encouraged since 2010 after the enactment of the Act for Promotion of the Use of Wood in Public Buildings. Obayashi has always worked on wood construction technologies, but with the enactment of the law, the company developed O・Mega Wood, which enables long-span wood frames to be built at low cost, and has completed many construction projects.
Timber supply is so abundant in Japan that it now exceeds local demand. Timber must be transported to and used in urban areas where construction demand is higher. In addition, people now prefer buildings designed with wood. There is an increasing demand for structures with wood that is visible, even in city centers.
The Building Standards Act requires buildings that are 100 m² or larger to be fire-resistant when constructed in fire prevention districts. Therefore, fire-resistant technology is necessary when building medium to large wooden structures in urban areas. However, there have been issues related to the cost of building long-span frames that are needed for medium to large structures, especially if they are fire-resistant and have wood on the surface. This is because of the complexity of producing the materials.
That is why Obayashi developed O・Mega Wood (FR) by adding a layer of combustible wood to quasi-fireproof O・Mega Wood, which contains fire-resistant gypsum board. O・Mega Wood (FR) provides three hours of fire resistance at low cost. It has a simple design with three layers of materials and the beautiful appearance of wood.

O・Mega Wood (FR)

The main features of O・Mega Wood (FR) are as follows:

  1. Provides up to three hours of fire resistance in wooden structures

    Previously available O・Mega Wood could be used for wooden structures that must be quasi-fireproof. With a fire-resistant layer and a combustible layer added to the surface of timber, O・Mega Wood (FR) provides up to three hours of fire resistance in wood structures. This makes it possible to build high-rise wooden structures with 15 floors or more, without the number of floors being restricted by the Building Standards Act. In addition, O・Mega Wood (FR) is also available in 1-hour and 2-hour fire-resistance specifications. Therefore, you can choose a cost-effective option depending on the fire-resistance performance required for the building.

  2. Provides the calming effect of wood

    O・Mega Wood (FR) has a combustible layer of wood on the surface. It provides the beautiful appearance and calming effect of wood. Any species of wood can be used as long as it meets certain criteria. You can choose specialty wood from a particular region, such as Japanese cypress from Kiso or Hiba (type of Japanese cypress) from Aomori for example, or whatever fits your design.

  3. Achieves fire-proof wood construction with long-span frames at low-cost

    Building long-span frames with wood requires pieces of timber with large cross-section width (thickness) and depth. In the past, it used to be necessary to take multiple pieces of laminated veneer lumber (LVL), which already have layers of veneers glued together, and join them with adhesives to make a thick plank. They tend to be expensive because they can only be produced at factories equipped with special machines and capabilities. O・Mega Wood is a technology that enables thick planks to be produced by integrating LVLs with fasteners such as screws without having to use secondary adhesives. It reduces cost and lead time by eliminating the secondary adhesion process at another plant.

The new O・Mega Wood (FR) has the above benefits but costs approximately 20% less than conventional large, cross-section wood construction technologies that require secondary adhesion. This is because it has a simple design with three layers of materials with a fire-resistant layer and an additional combustible layer. In addition, it does not require fireproof coating or finish unlike conventional steel construction. The overall cost could be about the same as for steel construction.

Components of O・Mega Wood (FR)

The new O・Mega Wood (FR) makes it possible to build fire-resistant wooden structures for a variety of uses, with wood that is visible and at low cost. These include buildings that must be fire-resistant such as educational facilities, medium to large offices, commercial buildings, and medical and welfare facilities.

Fire Resistance Test Under Load

Specimen before fire test
Inside the furnace during fire test
Specimen after fire test
Load-bearing material with the fire-resistant layer removed after fire test
(The material is in good condition with no burned area.)

Structural Load Test

O・Mega Wood Frame with CLT-wall
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