Designing and building three-story wooden apartment buildings has become more feasible thanks to relaxed standards. Properties that meet certain criteria are known as "Mokusan-kyo." This article explains the eligibility requirements for "Mokusan-kyo" and the benefits it offers investors.
What are the four requirements for "Mokusan-kyo"?
To qualify as Mokusan-kyo, a property must satisfy all four requirements related to fire-resistant construction, passage width, balconies, and fire protection equipment.
Fire-resistant construction requirement
The building must be a "one-hour quasi-fire-resistant building" capable of maintaining its structural integrity for one hour after a fire breaks out. Fire-resistant covering work is applied to walls, columns, beams, and the undersides of roof eaves. This requirement exists because evacuation takes longer in three-story apartment buildings.
Passages around the building
A passage at least 3 meters wide must be provided on the site. However, relief measures apply when an evacuation balcony is installed or when corridors and stairways are directly open to the outside air.
Balcony installation
A two-direction evacuation route using an evacuation balcony is required. However, a balcony is not required when the corridors and stairways leading from each unit to the ground are directly open to the outside air and equipped with fire protection equipment.
Fire protection equipment for exterior wall openings
In fire prevention districts and quasi-fire prevention districts, fire protection equipment is required for exterior wall openings in third-floor units. Relaxation may be possible through specified separation distances or the installation of projecting walls or eaves.
What are the benefits of investing in three-story wooden apartment buildings?
The biggest strengths of three-story wooden apartment buildings are lower construction costs and flexible design planning.
Construction costs can be reduced significantly
The market range per tsubo is 770,000 to 1,000,000 yen for wooden construction, compared with 800,000 to 1,200,000 yen for steel construction and 900,000 to 1,200,000 yen for RC construction. On a 50-tsubo comparison, a wooden building can in some cases cost up to 10 million yen less than a steel building and up to 15 million yen less than an RC building. Lower costs directly support faster capital recovery through rental income.
Unit count can be secured even on small or irregular lots
Wooden construction allows flexible design even on small or irregularly shaped sites where large heavy equipment is difficult to bring in. By going to three stories, it becomes possible to secure more units and increase floor area in ways that are difficult with a two-story building, helping maximize rental income.
Summary
The three-story wooden apartment building category known as "Mokusan-kyo" can deliver both lower construction costs and greater design flexibility when the eligibility requirements are met. Because it can also be used on small or irregular lots, it is a strong option for land utilization. When evaluating an investment, confirm the four requirements before moving forward with the plan.
Frequently Asked Questions (FAQ)
- Q. Which requirement matters most for qualifying as Mokusan-kyo?
- A. All four requirements are mandatory, but ensuring the one-hour quasi-fire-resistant structure has the greatest impact on design and cost in particular.
- Q. Is a three-story wooden building less durable than a steel-frame building?
- A. With proper maintenance, a wooden building can also remain serviceable for 50 to 60 years. Consider investment efficiency together with the advantage of lower initial costs.
- Q. Can Mokusan-kyo be built anywhere in Japan?
- A. Regulations differ in fire prevention districts and quasi-fire prevention districts, so confirm the zoning of the planned site and consult the local building authority.
