By Eric Moshier – Certified Heater Mason, Third-Generation Mason, MHA Technical Committee Member, ASTM E1602 Masonry Heater Group Member
In March 2022, Solid Rock Masonry LLC of Duluth, Minnesota built a round, white glazed Swedish style tile stove, a kakelugn, in Stockholm, Wisconsin. It has a Russian bell core. Every tile on it was made by hand by Sharon Moen of Falconfire Pottery in Duluth. The stove burns a hot, fast fire for 2 to 3 hours and radiates heat back into the room for the next 12 to 24 hours. This is the whole build, in order, from the first sketch to the brass doors going on, photographed over four months and four days on site. Site-built masonry heaters like this one run $30,000 to $40,000.
Most project photos on a masonry website are the last photo. The stove is done, the room is clean, the light is good. That photo tells you nothing about how it was made.
This is the other kind. Every image here has a timestamp, and they are in the order they were taken.
16 November 2021: the drawing
The Schabels came to us with a photograph of an antique Swedish tile stove. A round white column, a stepped base, a brass door. They did not want that exact stove. They wanted that form, in their house, in a curved alcove that had already been tiled sage green.
That is harder than importing an antique. An antique arrives as a crate of numbered tiles and a map for putting them back. This one had to be invented.
So it was drawn, and then modeled, before anyone touched clay. On a round stove the tile has to be manufactured to fit the heater, because you cannot cut your way out of a mistake on a cylinder. Get the radius wrong on one tile and it is wrong by a lot by the time you close the circle.
30 November 2021: Sharon makes the tile
Two weeks later, in a pottery studio in Duluth at eight o’clock at night, the first course was laid out on the floor to check the radius.
Every tile on this stove is a segment of a circle, curved to a specific radius, with a keyed back that locks into mortar. There is no supplier for this. Somebody has to make them, one at a time, over a mold.
Ours were made by Sharon Moen of Falconfire Pottery. She has been a studio potter for over twenty years and came to clay by way of a master’s degree in ecology, which tells you most of what you need to know about how she approaches a problem. She formed every tile, glazed it, fired it, and dry-fit the whole first course before committing.
Then the tile went on a shelf and waited three and a half months for the masons.
Day 1 – Monday 14 March 2022, 2:13 pm: the base
The alcove, before. Slate hearth set, sage green wall tile already in place, firebrick staged on the floor.
The first course goes down in a mortar bed and it has to be dead level and dead round, because everything above it inherits whatever you do here. By 4:24 pm the base ring was complete. By 6:22 pm the firebrick firebox floor was laid.
Nine hours in, and the stove is a ring on the floor.
Day 2 – Tuesday 15 March, 8:25 am: the firebox
The custom SR-13 steel firebox door and its brass surround get built into place as tile goes up around the door. Then the firebox walls: fireclay firebrick, laid tight, joints as thin as we can get them. The tile are set with a 3 part mason sand : 1 part hydrated type S lime : 1/4 part portland mortar mix. Which is softer than the fired tile.
Around the firebox goes ceramic fiber. It does two jobs. It insulates, and it gives the core somewhere to expand into. A masonry core moves when it heats. The tile shell does not. Bond them rigidly together and the tile cracks, and it cracks in the first winter. That gap is not sloppiness. It is the whole reason the stove survives.
Firebox masonry thicknesses and clearances to combustibles are set by ASTM E1602, referenced by IRC Section R1002. I sit on that committee. Those are the first numbers an inspector will measure. More on masonry heater building codes.
At 6:07 pm the throat was cut. That is the opening at the top of the firebox where hot gas leaves the fire and turns into the bell above.
Day 3 – Wednesday 16 March, 6:48 am: the bell
The biggest day of the build. The crew started before seven in the morning and worked until after five. This was the day the stove became a heater.
Why a Russian bell and not Swedish channeling
A traditional kakelugn uses a Swedish five-run channel system: flue gas led up and down through five narrow passages before it reaches the chimney. It works, and it has worked since 1767.
But a five-run system is, functionally, a series of small bells. In each run the hot gas rises, gives up its heat to the masonry, cools, falls, and moves on. That is bell behavior. The Swedish system is not a different principle from the Russian bell. It is the same principle, subdivided.
So we built one bell instead of five runs. Same physics. Fewer parts. And a single bell is far easier to clean and far harder to build wrong than five narrow channels stacked inside a cylinder. The stepped form of this heater, wide at the base and narrower above, gives you a generous bell chamber sitting exactly where you want one.
A Russian bell was not a compromise here. It was the simpler expression of what the Swedish stove was already doing.
At 7:13 am the refractory slab that separates firebox from bell was laid out with a template and marked by hand. Twenty-one inches. At 8:22 am it was set, with the throat cut through it. Everything above that slab is bell.
By 12:16 pm the clay flue liner was standing inside the bell. This is the part that surprises people: gas rises around the outside of that liner, gives up its heat to the surrounding masonry, cools, falls, and only then enters the liner and goes up the chimney. By the time it leaves, most of the energy that was in the wood is in the masonry, not in the sky.
That is why a masonry heater burns a fire for 2 to 3 hours and heats a house for 12 to 24.
From 2:49 pm the tile shell started climbing, each tile bedded in lime mortar and tied together with a wire clips made to tie each tile to the one next to it. The outer structural tile (kakel) is basically free floating though the tile ring is all connected. The kakel are separated from the core with the 2 layers of brown “ram board”. This allows for the firebrick core of the heater to move and expand up at a different rate than the outer kakel or tile. This helps to minimize cracking in the joints.
Day 4 – Thursday 17 March, 7:30 am: the mark
The first photograph of the last day is not of the stove. It is of the back of a tile.
When we rebuild an antique Swedish kakelugn, we routinely find the potter’s stamp pressed into the back of a two-hundred-year-old tile. It is the only signature on the entire stove, and nobody ever sees it except the mason who takes it apart.
Sharon’s mark is on the back of these. In two hundred years, somebody is going to take this stove apart and find it.
The top slab was parged around the flue collar by 8:13 am. The last course of tile went on at 9:38.
At 12:52 pm, the brass doors.
What it is
A Swedish style tile stove in every way that matters to the eye, and a Russian bell heater in every way that matters to the fire.
Four days on site. Three and a half months of tile before that. One drawing before that. And a maker’s mark on the back of a tile that nobody will see again for a very long time.
Frequently asked questions
Is this a real kakelugn?
It is a Swedish style tile stove built to the kakelugn form, with handmade curved tile and a stepped round column. The interior is a Russian bell rather than a Swedish five-run channel system. Both work on the same principle, and the client knew that from the first drawing.
How long did it take to build?
Four days on site, 14 to 17 March 2022. The tile was designed in November 2021 and made over the following weeks. The lead time on handmade tile is almost always the longest part of a project like this.
Who made the tile?
Sharon Moen of Falconfire Pottery in Duluth, Minnesota. Every tile was formed, glazed, and fired by hand for this one stove.
What does a stove like this cost?
Site-built masonry heaters run $30,000 to $40,000 depending on size, tile work, and site conditions. Handmade tile is a separate cost and depends entirely on the design.
Can you build one for me?
Yes. We build custom masonry heaters nationwide from Duluth, Minnesota, including Swedish style tile stoves, kachelofen, Finnish contraflow heaters, Russian bell heaters, and wood-fired bake ovens. Start with our planning process or read more about the kakelugn.
Solid Rock Masonry LLC
5347 Howard Gnesen Road, Duluth, MN 55803
218-343-2978
eric@solidrockmasonry.com