Design Performance Evaluation

The Company is actively promoting the use of the Japan's Housing Performance Indication System*¹ for customer peace of mind and safety as well as enhancing the value of property. In fiscal 2023, under this system, implementation rate^*2 of Design Performance Evaluation reached 99.8%, Implementation of Construction Performance Evaluation reached 99.7%, and the acquisition of Long-life Quality Housing Certification reached 95.9%.

*1 Third-party evaluation system for design performance at the time of design and of construction performance upon completion so that customers can objectively assess the quality and performance of a house

*2 The ratio of the number of applications against the total number of detached houses constructed, including extensions and/or alterations (applications for design and construction performance evaluation, January 01, 2023 - December 31, 2023) in the Housing Division

*The aggregation period for fiscal 2021 and onwards is from January to December of each year, the aggregation period for fiscal 2020 is from April to December

Long-life Quality Housing Certification

Sumitomo Forestry sets the standard specifications for its Sumitomo Forestry Homes to exceed the highest level of Long-life Quality Housing^*1 certification conditions^*2 (applying the evaluation under the Japanese Housing Performance Indication System). From product development through to construction and after-service, the Company has established its framework for product safety and quality control in order to deliver high quality homes with superior overall balance.

*1 A life-long housing certification system of Ministry of Land, Infrastructure, Transport and Tourism which aims to popularize housing that will help realize a society that values its housing stock

*2 Detached housing is evaluated for durability, seismic resistance, ease of maintenance and energy efficiency in accordance with the Japanese Housing Performance Indication System

*The aggregation period for fiscal 2021 and onwards is from January to December of each year, the aggregation period for fiscal 2020 is from April to December

*The higher the rated level, the better evaluated

Framework for Product Safety and Quality Control

Product Development

• Undertaking development of housing products incorporating new technology, materials and lifestyle, based on consumer needs and owner surveys
• Housing Division and Tsukuba Research Institute are collaborating in experiments at validation facilities and testing of prototypes, promoting the creation of products that incorporate customer feedback, including even in the details of guarantees

Design

• Sumitomo Forestry uses a unique system to check design and structure at the time of contracting and through the final design stage

Materials Procurement

• The Materials Selection Subcommittee, which meets once every month to decide upon all materials, conducts design reviews. All materials are checked to ensure that they meet the acceptance and quality standards set by the Tsukuba Research Institute and the Materials Selection Subcommittee
• After approved by the Materials Selection Subcommittee, materials are subjected to a further design review after actual on-site use (approximately two years later) to confirm whether the planned quantity can be shipped and whether or not there are any quality defects

Construction

• Sumitomo Forestry centrally manages and shares up-to-date information on the construction, process management, quality control and safety management of each building through its own site management system
• Each on-site operator, contractor manager and construction manager during such stages as foundation, construction and completion, conducts inspections which are managed using a construction management record. Additionally, the Head Office inspection division checks the status of the inspection and management

After-sales Support

• Sumitomo Forestry includes free regular inspections with its homes. After the 10th year, owners can extend the building warranty by going through the paid maintenance constructions according to maintenance plans; then free regular inspections will continue after the 30th year until the 60th year. 60 years of support to ensure the longevity of your home (may vary due to the timing and details of the contract)
• Sumitomo Forestry has developed a 60-Year Maintenance Program that offers renovation and maintenance proposals and manages maintenance records in order to support home owners

Renovation

• The performance and reliability of Sumitomo Forestry's proprietary materials used in anti-seismic reinforcement and other applications are verified at the Tsukuba Research Institute. In addition, we are advocating seismic retrofitting by undergoing a technological evaluation of the Japan Building Disaster Prevention Association

Seismic Resistant Housing

The Great Hanshin-Awaji Earthquake and the Great East Japan Earthquake , the Kumamoto earthquake, and the most recent Noto Peninsula earthquake that struck on January 1, 2024 have been among the disasters that have wrought enormous damage in Japan. In addition, major earthquakes are forecast to occur in the Nankai Trough, resulting in year-by-year increase in demand for seismic resistance for wooden houses.

In response to customer need for seismic-resistant houses, Sumitomo Forestry Home Tech has developed original construction methods that enable heightened seismic resistance without diminishing high levels of the home's structural strength, workability or insulation efficiency, such as installation into existing floors and ceilings without any removal and disposal.

Development of K-shaped Corner Braces and Hyper Panels

K-shaped corner brace bearing walls use 24 mm thick structural plywood that is in order to store 75 mm thick glass-wool insulation inside. This method has great workability because the materials are light, and it underwent a technological evaluation by the Japan Building Disaster Prevention Association (6.0KN/m² standard bearing wall).

Hyper Panels reduce removal work by only having to remove the gypsum board between existing flooring and ceilings. Hyper Hard T (Yoshino Gypsum Co., Ltd.) improves workability by dividing a high-strength board into three pieces for installation so that each board can be applied. This three-piece design enhances the bending strength without the board breaking. The method also received a technological evaluation by the Japan Building Disaster Prevention Association (6.9 KN/m² bearing wall for the standard type).

Moving forward, we plan to develop new vibration dampers and approaches to seismic resistance that can reduce damage to buildings during major earthquakes to the greatest possible extent.

Construction Method (BF Construction Method)

Sumitomo Forestry started selling the Big-Frame Construction Method (BF Construction Method) for three-story building products in 2005 and expanded this method to two-story products in 2008 as well as to products with fire-resistant specifications in four-story buildings in 2015. Thereafter, as awareness of customers grew about disasters and other risks, the BF construction method that had further evolved to provide greater strength in high seismic resistance matched customer needs and is now one of Sumitomo Forestry's main products.

Wooden Beam Rahmen Structure

The proprietary BF construction method from Sumitomo Forestry is the first in Japan to realize the wooden beam Rahmen structure, which is used in high-rise buildings, in wooden houses.

The Rahmen structure is designed to stand up to horizontal forces such as earthquakes and wind through rigid-joints that unify the columns and beams with the fixings. The BF construction method uses big columns with a large cross-section of 560 mm, which is equivalent to roughly five standard 105 mm columns , and “Metal-Touch” joints fastened with hardware to achieve a robust Rahmen structure.

“Metal-Touch” (Metal-to-Metal) Joint

Special screw-shaped bolts are embedded in the big columns and beams, which are then joined with the special hardware on the big columns, beams, and foundations to ensure a strong fit. This "Metal-Touch" joint makes it possible to create both large spaces and large openings while ensuring earthquake resistance.

Introducing and Expanding Original Joining Technology

The BF construction method enables introducing and expanding a variety of original technologies and can support an even wider range of design requirements. Twin-bolt columns that doubles metal joints as well as double-large columns that layer two large columns provide freedom in floor plans and more spaciousness even on land with many restrictions. The pre-stressed timber beams, which allows for a maximum opening width of up to 7.1 meters, enable the design for built-in garages ready for parking multiple vehicles, large open living rooms, multi-dwelling homes in addition to a wide range of other purposes.

Confirmation of Performance by Full-Scale Vibration Test

Sumitomo Forestry conducted vibration testing using a full-scale test model of a 3-story building built with the BF construction method and the actual floorplan.

For this testing, the building with BF construction method withstood the maximum acceleration of 2,699 gal, equivalent to the Great East Japan Earthquake, proving its strength against major earthquakes. Our technology has been proven tough through a total of 22 harsh vibration tests; two of which were conducted at a magnitude of 7 equal to the Great East Japan Earthquake and 20 of which equal to the Great Hanshin-Awaji Earthquake. Furthermore, assuming repeated strong aftershocks, we have confirmed that the seismic resistance of the structural framework will continue to be maintained even after 224 repetitions of severe shaking of intensity 4 to 6, for a total of 246 repetitions of shaking.

In this way, the BF construction method responds to the needs of customers with powerful structures to bring security as well as flexible designs able to provide comfortably spacious spaces.