Study on development and application of factory production methods
for profit structure improvement of light frame wood structure industry.
Department of Forest Products and Technology, Graduate School
Chungnam National University
(Supervised by Professor Sang-Sik Jang)
* A dissertation submitted to the committee of Graduate School, Chungnam National University in a partial fulfillment of the requirements for the degree of Doctor of Philosophy conferred in August 2014.
Most of the framework of light frame wood structure in Korea has been subcontracted by framework master teams. Framework master team construct building with simple floor plan and elevation plan which have not details of frame. So, framework team directors bear responsibility about size, angle and fabrication of lumbers. Because of this methods, wooden houses is made defect by a shortage of framework teams and mobilization of unskilled labor in busy season. And marketability of wood construction can be declined by fall in the consumer confidence.
The light frame wood structure industry need not expensive equipments and factories. And because finish work and equipment work are subcontracted with specialty contractors, carpenters learning wood structure and woodwork can easily contract with clients without the business registration. Quality and prices of wooden houses have been fallen by imprudent increases of companies and carpenters by the wrong market structure. In order to resolve this problem, some companies conduct high-quality strategy, exaggerated internet advertisements. But, Because these solutions are temporary method, the ultimate solution should be to raise quality over the maintenance of prices or cut prices over the maintenance of quality.
The factory production is one of important methods in order to resolve this problem. And this method would rather on-site construction method with precut materials than prefabrication method by road conditions and dwelling house size. Because the factory production must have to has factories and labor force for factories, profits of the factory production should be very higher than common on-site production.
This study took to make exclusive framework drawing, precut materials in factory and construct house. Then, made a comparison between the factory production and common on-site production.
In the results, the percentage of profits was forecasted about 30%(labor cost) and 13%(material cost). It is thought that additional profits can be caused by the reduction of labor cost under factory automation and the increase of profits under proficiency of labor.
Today, many clients demand modern design. The shed roof of modern design would rather trusses than rafter system, but, rafter system is generally used in Korea. In this study, trusses were manufactured by using oriented strand board (OSB) gusset plates. Then, trusses tested under the bending load and constructed on-site. In this results, although the allowable strength of OSB gusset trusses was measured less than metal gusset trusses, 6m span roof with OSB gusset trusses is sufficient for use in construction. The percentage of profits was forecasted about 24%.
It is thought that the domestic industry of wooden houses will change common on-site production into factory production. To activate the factory production in Korea, Constructors and framework teams should admit the outdated conventional site system and deal with changes. By this study, It is expected to help the domestic wood structure industry to replace the common site production with the factory production.