Design Performance Evaluation

Sumitomo Forestry is actively promoting the use of Japan's Housing Performance Indication System*¹ to ensure the safety and security of customers and enhance the value of their property. In fiscal 2025, under this system, the implementation rate*² of Design Performance Evaluation reached 99.9%, and the implementation rate of Construction Performance Evaluation reached 99.7%. The acquisition rate of Long-life Quality Housing Certification was 97.4%.

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

*2The 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, 2025 - December 31, 2025) in the Housing Division

Long-life Quality Housing Certification

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

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

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

*The higher the rated level, the better the evaluation result

Framework for Product Safety and Quality Control

Product Development

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

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 one and a half 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 offers free-of-charge regular inspection service to the owners of Sumitomo Forestry homes for 10 years after the completion of the homes. The owners can extend the free-of-charge regular inspection service period until the 60th year, on the precondition that they pay for the repair service provided by the company based on a maintenance plan and thereby extend the warranty period for the building. We offer 60 years of support for the longevity of Sumitomo Forestry homes. (Details of the support service may vary depending upon the timing and details of the contract.)
• Sumitomo Forestry has developed a 60-Year Maintenance Program to offer renovation and maintenance proposals and manages maintenance records, thereby supporting owners of Sumitomo Forestry homes.

Renovation

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

Seismic Resistant Housing

Major earthquakes causing extensive damage have occurred across Japan, including the Great Hanshin-Awaji Earthquake (Hyogo Prefecture Southern Earthquake), the Great East Japan Earthquake (Tohoku Pacific Ocean Earthquake), the Kumamoto Earthquake, and the Noto Peninsula Earthquake on January 1, 2024. In addition, because the probability of a Nankai Trough earthquake within the next 30 years has been raised from " around 80%" to "up to around 90%," there has been growing demand in recent years for seismic retrofitting of wooden houses.

In response to customers' needs for seismic retrofitting, Sumitomo Forestry Home Tech has developed original methods to easily reinforce the seismic performance of buildings without compromising the building's insulation performance, including using load-bearing walls that can be installed without dismantling existing floors or ceilings.

Development of Corner Brace Panels and the Sumirin Hyper Panel Construction Method

For the corner brace panels, we use 24 mm-thick structural plywood, and the panels are designed to accommodate 75 mm-thick glass-wool insulation inside. The panel is easy to install because the materials are light, and it has undergone technological evaluation by the Japan Building Disaster Prevention Association (6.0KN/m standard bearing wall).

The Sumirin Hyper Panel construction method is intended to enhance seismic resistance by combining rigid gypsum boards, metal fittings, and structural plywood. In addition, the existing floors and ceilings do not need to be dismantled, and workability is improved by dividing the rigid gypsum boards, which are nearly twice the weight of standard gypsum boards, into three parts before attaching them to the walls. The method also received a technological evaluation by the Japan Building Disaster Prevention Association (6.9 KN/m standard bearing wall).

In the future, we plan to develop new seismic and vibration control methods that will help minimize the damage that may be caused to buildings during major earthquakes.

Big-Frame (BF) Construction Method

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

Wooden Beam Rahmen Structure

Sumitomo Forestry’s proprietary BF Construction Method 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 helps meet a wider range of design requirements by the application of a variety of original joining technologies. The Twin Bolt Column, composed of two rows of metal connectors, and the Double Column, comprising two large columns placed side by side, enhance the flexibility of floor plans and create a more sense of openness even on sites with many constraints. The pre-stressed timber beams, which allow for a maximum opening width of up to 7.1 meters, increase the design flexibility for a built-in garage for parking multiple vehicles, large open living rooms, and mixed-use houses.

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 withstood the maximum acceleration of 2,699 gal, equivalent to that recorded at the time of 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 that of the Great East Japan Earthquake and 20 of which at a magnitude equal to that of the Great Hanshin-Awaji Earthquake. Furthermore, assuming repeated strong aftershocks, we have confirmed that the seismic resistance of the structural framework will 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 diverse needs of customers with powerful structures to bring security as well as flexible designs able to provide comfortably spacious spaces.

Promotion of Universal Design

In addition, we are committed to creating safe and secure homes and developing products that support the healthy growth of children, such as “Mannaka Kodomo BASE," where children can play while feeling the presence of their family, and the PRIME AIR Original Air Conditioning System for whole house ventilation and humidity control, which provides a healthy room environment for children.

In addition, we are committed to creating safe and secure homes and developing products that support the healthy growth of children, such as “Mannaka Kodomo BASE," where children can play while feeling the presence of their family, and the PRIME AIR Original Air Conditioning System for whole house ventilation and humidity control, which provides a healthy room environment for children.

First Class Architects in the Housing Division

The Housing Division has 898 first class architects on staff (as of April 1, 2025), representing 20.4% of the division's total workforce. This is one of the highest rates among housing manufacturers, and is the reason for the high construction quality of Sumitomo Forestry homes.

Maintain and Improve Construction Quality

The Housing Division strives to properly manage the supply chain to maintain and improve the construction quality of Sumitomo Forestry homes. In order to continue appropriate transactions with suppliers, we make maximum use of "factory audits" and "supplier evaluation" by component.

Factory Audit

The purpose of a factory audit is to ascertain the production process, quality control status, raw material procurement status, etc., for the parts and materials to be purchased.

Based on the Quality Audit Program & Implementation Plan, we target 126 supplier factories nationwide to ascertain their actual conditions through interviews with relevant personnel and visual inspections at the suppliers’ factories. In addition, corrective actions are requested during factory audits if there are items to be improved.

Supplier Evaluation

The supplier evaluation includes a comprehensive assessment of the supplier's factory audit results, financial condition, quality control status, delivery time, costs, and BCP measures. We will check whether or not the manufacturer/product is up to the standard required by Sumitomo Forestry and provide feedback on the results to encourage the suppliers to make improvements as required.