Blog Entry

Nagano, Japan: Stucco Contraflow Masonry Stove

August 11, 2013 by , under Fire Works Masonry News.

Fire Works Masonry’s latest job was an outstanding opportunity to build a masonry stove for our friend and Masonry Heater Association colleague Aki Yoshimizu in his lake cottage in Nagano, Japan. Aki is a builder in Japan and is the owner of Peak Home Builders. The photo below shows the functioning, almost complete heater.

Aki Japan Masonry Heater

The heater was designed by and built with MHA founding member Norbert Senf of Masonry Stove Builders from Quebec, Canada. Norbert also posted a detailed photo report of the entire project on the MHA News E-zine.

The energy efficient fireplace is a Finnish contraflow core based on the Masonry Heater Association’s Heater Plan Portfolio. The fireplace is faced with dense brick pavers. The rough stucco coat will be finished in a local Japanese clay plaster. The photo below shows the first small curing fire burning in the firebox.

Japan Masonry Stove Complete Facing 0922b

The lakeside cottage is located in a beautiful rural setting. Like many homes in Japan, the home is not well insulated and can be a challenge to heat in the winter. The mountainous area regularly gets heavy snow falls and temperatures as low as 0F. Aki became interested in the possibilities to heat efficiently and cleanly with locally available firewood.

Japan Fireplace Cottage 0431

The photo below shows the great view of the quiet lake from our workroom door.

Japan Masonry Heater Lake 0805

The heater starts with the layout. The masonry stove will have a very unique heat exchanger design for the upper bedrooms designed by Norbert.

Japan Masonry Heater Core Layout 0766

Once we establish the layout, the base courses of the fireplace begin. The photo below shows a new layout design for the contraflow base designed by MHA member Eric Moshier.

Japan Masonry Stove Core Base Courses 0818

Aki hosted the build as a workshop and several interested and adept volunteers attended. The photo below shows Norbert Senf, Mamoro Ooishi, Yuuichi Kada, and Takeo Onozawa.
Mamoro is a chimney sweep and woodstove salesman from Hokkaidou. Yuuichi is a mason and garden craftsworker
from Aichi, about four hours away, and Takeo (Ono) is a chimney sweep from Nagano. They met while doing volunteer
work after the Tsunami.

Japan Energy Efficient Fireplace Work Crew 0887

With so many helping hands, the build goes quickly.  The photo below shows the completed firebox and the start of the throat behind the white oven.

Japan Masonry Heater Core Bake Oven 0857

The white oven slabs are installed. Aki is a carpenter and builder. He made excellent forms and castings for the high temperature concrete slabs.

Japan Energy Efficient Fireplace Bake Oven 0881

The final courses and secondary combustion chamber are completed above the bake-oven.

Japan Energy Efficient Masonry Fireplace Core 0899

The two side downdraft channels can be built next.

Japan Masonry Heater Core Side Channel 0916

Once the side channels are complete the crew installs the heavy high temperature capping slabs.

Japan Masonry Heater Core Capping Slabs 0009

With the core completed, the crew enjoyed a great evening campfire and cookout.

Japan Masonry Heater Full Moon 0294

Japan Masonry Stove Campfire 0196

The masonry stove work begins again the next morning. Locally available dense, red brick pavers will face the core.

Japan Masonry Fireplace Face Bricks 0947

The bricks are delivered to the jobsite. The local hardware store allows customers to borrow this small pickup for 90 minutes with no charge. These useful small pick-up trucks are everywhere in Japan. The truck gets about 50mpg, carries over 700lbs and costs under $9,000.

Japan Masonry Heater Delivery Truck 0873

The photo below shows the start of the face brick, chimney connection, and small heated bench.

Japan Brick Fireplace Facing and Chimney Start 0146

The heater installation is in a seismic zone. Threaded rods are drilled and epoxied into the base concrete slab. The rods will be buried in the mortar slush between the core and facing. A steel plate on top of the heater will bond the masonry and rods together.

Japan Masonry Heater Facing and Seismic 0268b

The brick facing is about halfway complete after a long day. The jack arch spanning the door openings is the next step.

Japan Masonry Stove Brick Facing 0308

Norbert inserts the keystone into the jack-arch. The jack-arch is left proud from the brick facing for a design element.

Japan Masonry Stove Jack Arch 0353

The brick facing progresses. The photo below shows the closing keystone for the second jack-arch above the bake-oven door.

Japan Masonry Stove Bake Oven Brick Arch 0481

Norbert’s heater design also includes a unique curved brick wall surrounding the chimney connection. The curved section is seen in the photo below.

Japan Clean Burning Fireplace Curved Chimney Design 0517

The final brick courses are nearly complete in the photo below. One of the threaded rods for the seismic reinforcing can be seen above the brick to the right.

Japan Masonry Heater Brick Face0535

With the brickwork completed, the stucco plaster coat begins. Aki looks admiringly at the brick face while he holds a fiberglass mesh in place to reinforce the plaster facing.

Japan Masonry Stove Plaster Coat 0564b

Later that evening the crew burns the first small curing fire around the completed rough coat heater.

Japan Stucco Masonry Fireplace First Fire 0702

With the rough plaster coat completed, the doors are installed into the brick facing.

Japan Masonry Stove Wood Fired Oven Door Installation 0732b

The photo below shows the nearly completed, clean burning, energy efficient fireplace with another small curing fire. The heater still needs the final plate for the seismic reinforcement, a small top for the heated bench, and a final decorative plaster coating. Aki will most likely use a local, traditional clay or lime plaster.

Japan Masonry Stove Complete Facing 0922b

 

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