Located at Lake Chuzenji in Nikko city, the On the water project replaces a 5-story corporate retreat facility with a new, summer guesthouse for a private client. This two-story building is located on a sloping site that has a level difference of 7m, from the road down to the lakeside. Access from the road is at the 2nd floor level and circulation is orchestrated through a welcoming dining space and through a spiral configuration of spaces finally to the guest bedrooms on the 1st floor. The 1st floor plan brings in the lake water to an inner garden by removing the shoreline protection work that existed between the lake and the previous building. The scenery of the lake is framed by a large floor slab spanning 20m, which extends over the garden area.

The porch area on the 2nd floor continues to the dining space covered with a steel frame cantilevered roof. The sofisticated structural design prevents the roof from deformingunder heavy snow load, as suspension tension becomescountered by thesnow load. By managing the deflection of the roof against snow load, it becomes possible to utilize large-scale sashless glazing to maximize the vistas to the lake.

To guarantee the best panoramic view, a BIM model was utilizedto study the topography and find the ideal location. The use of the Bim model was also essential to balance the scale of each room, together with the shape and height of the openings,with the visual sequence and circulation inside the building.It also simulatedtechnical performance including roof deflection under snow fall, the natural ventilation, and the thermal environment resulting from the heat of the fireplace in the lounge; as well as helping to define finishing materials and placement of furniture.

This guesthouse was designed as a continuous spiral space flowing from the approach to the bedrooms. Each step taken deeper inside the building reveals a changing lakefront view. The various lakeside environments, including the sound of ripples, light reflecting from the water surface, the humidity and thermal radiation, are also carried on into the spiral, but in a non-uniform distribution due to changes in physical distance from the water surface. Since the whole structure is an interconnected space with different elevations, there is no homogeneous environment— with various areas presentinga range of differing thermal conditions.

Located in a natural environment that requires heating in the building even during the summer nights, guests are able to wander around, discovering and enjoying spots they find comfortable. Some may find joy in the warmth near the fireplace, while others may relish the area’s tranquility and cool characteristics in other spaces. The building is put to sleep during the harsh winter season to prevent wasteful use of energy.

Material Used :
1. Structural system: reinforced concrete
2. Major materials: exposed concrete, glass, stainless galvanized steel plate / exterior exposed concrete, wood flooring, plaster finish / interior
3. LIXIL: System kitchen
4. GROHE: Toilet bowl, water faucet
5. JAXON: Bathtub
6. AGC Glass Building Material: Glass
7. METAL ARCHITECT KIKUKAWA: Stainless steel sash

Exterior Finishes
1. Roof: Hot-dipped Zinc Galvanized Stainless Steel Sheet
2. Eaves: Resilient Resin Spray Coating 
3. Exterior Walls: Fair-faced Concrete Finish, Wooden Board Clad
4. External Floor: Crushed Stone Paving, Fair-faced Concrete, Bush-Hammered Finish
5. External Fittings: Stainless Steel, Black Nickel Galvanized

Interior Finishes
1. Ceiling: Resilient Resin Spray Coating (Limited to interior ceiling which is continuous from External Ceiling.), Other than this area: Plastered Ceiling
2. Walls: Fair-faced Concrete Finish, Wooden Board Clad, Plastered Wall, Melted-Metal Spray Finish
3. Floor: Fair-faced Concrete, Bush-Hammered Finish, Wooden Flooring