Earthquake resistance, performance, cost｜FREEHOUSE NAVI

SJ Construction Method (Strong Joint Method)

The SJ construction method significantly reduces the portion of wood to be cut to 5% or less. Because this method uses hardware directly on the wood, it has excellent earthquake resistance and durability. Conventional construction methods remove a large 54% of the wood, making the most important joints thinner and less than half as weak.
It is strong enough to withstand an earthquake of intensity 7 class.

Joint strength: 1.7 times stronger
Pull-out strength: 3.1 times

DATA

4" hardware construction method is still about 1% of the total.
That is why it is attracting attention for its differences.

The number of pre-cut buildings is 3,920. Of these, 30 were built using the 4" metal hardware method, which is a very small percentage of the total.

Pre-cut results

3,920 buildings

4" metal hardware construction method

30 buildings

Adoption ratio

Approx. 1

Hardware construction method accounts for approx. 6% of the total. Conventional construction methods are still the mainstream.

The 4" metal hardware construction method is still a construction method with limited adoption among general specifications.
For this reason, it is one of the options worth comparing and considering for those who want to choose a home that is also structurally sound.

Construction Method Breakdown	Number of houses
4" metal hardware construction method	30 houses
3.5" metal construction method	190 houses
3.5" conventional construction method	3,600 buildings

*C.S. Lumber Co. results (April 1, 2025 - March 31, 2026, based on data provided)

Source: Tatsumi Corporation

■Ground investigation, solid foundation, and roof

Ground investigation strengthens the foundation (ground) on which the house is built. The solid foundation provides not only strength but also measures against moisture and termites.
To reduce the burden on the building, a roofing material that is half the weight of ordinary Japanese roof tiles is used as standard to reduce earthquake shaking.

■ Seismic dampers (MAMORY): Also used in Kumamoto Castle

By installing a seismic damper ( No.1 option in popularity ) that uses special rubber to "control" shaking, repeated earthquake countermeasures of earthquake resistance and seismic damping are possible.
*Since this is an optional feature, a separate cost will be incurred.

02. Housing Performance Evaluation

Beginning with new applications for detached houses for sale in December 2023, we have standardized* to obtain the highest grade in the three categories of the Housing Performance Indication System. We have obtained both a Design Performance Evaluation Certificate and a Construction Performance Evaluation Certificate after passing a rigorous review by a third-party organization accredited by the Ministry of Land, Infrastructure, Transport and Tourism. *This may not be applicable depending on the plan requirements of the property.

03. Cost

Although our homes are built for sale (for sale) at the lowest possible cost for the minimum necessary items, we offer quality better than custom-built homes, including freedom to choose the size and shape of the land, and the layout, specifications, and colors of the building.
In particular, we include all necessary items (such as exterior construction) in the cost estimate, so the price is several percentage points lower than other companies that deal mostly in custom-built housing.
Furthermore, we are able to offer our clients lower costs for infrastructure, ground reinforcement, and exterior work, etc., which are separate costs and separate contracts even for custom-built housing, by taking advantage of our know-how.

04. Technology

Free Housing has the technology to make full use of the space available on the site.
For example, we can build a house on a narrow lot with a total area of 35 m2 (10.5 tsubo) through planning and technology.
If there is a 25cm gap between the lot and the adjacent lot, we have the technology to put up a building wall there.
We also have the technology to construct lofts and stairwells by constructing the roof just short of the diagonal restrictions, even though most houses are built in the same direction and at the same angle.
We are convinced that this will maximize the effective use of your funds.

06. Total Proposal

At Jiyu Jutaku, the three departments of sales, planning, and construction management are in charge of the customer for the rest of his/her life.
The customer and these three persons are always on the same line to discuss interior coordination and original furniture to further enhance the customer's dream.
This remains the same even after the handover. For customers who are looking for a remodeling to accommodate lifestyle changes or for properties, we are able to quickly introduce unpublished information purchased by the sales company prior to settlement.
We can also provide consultation on various after-sales services, such as replacement of property, sale, and inheritance.

Earthquake resistance, performance and cost

Learn about free housing

Workmanship and Quality

01. earthquake resistant (1.6 to 1.7 times stronger)

4-sun pillar (12cm square)

SJ Construction Method (Strong Joint Method)

Reference: Tatsumi Corporation YouTube channel