Solid Rock Masonry LLC builds custom stone fireplaces in Duluth, Minnesota, the North Shore, the Iron Range and northwest Wisconsin, within about 1.5 hours of Duluth. Owner Eric Moshier is a third-generation mason with 40+ years in the trade, a Certified Heater Mason, and a member of the MHA Technical Committee and the ASTM E1602 committee. We have completed more than 800 projects.
We build stone fireplaces in fieldstone, Lake Superior stone, granite, limestone, river rock and brick. Most are built around a hand-built Rosin curved-back firebox, the design behind the Prior Fire, and we also build Rumford and see-through fireplaces, outdoor fireplaces, cooking fireplaces and fireplace and bake oven combinations. In addition, a large share of our work is finishing gas fireplaces and wood-burning inserts, and we work in natural stone only.
Stone facing on a gas fireplace or insert typically runs $5,000 to $8,000. A custom all-masonry stone fireplace typically starts around $50,000. Either way, every one is built to the 2024 International Residential Code and your local code.
By Eric Moshier - Certified Heater Mason, Third-Generation Mason, MHA Technical Committee Member, ASTM E1602 Masonry Heater Group Member
What kinds of stone fireplaces do we build?
Most of our stone fireplaces are one-of-a-kind, because they are designed around the room, the stone and how the owners want to use the fire. Over the years that has included:
- Rosin curved-back fireplaces, built by hand on site, our standard firebox for masonry fireplaces
- Classic interior stone fireplaces in fieldstone, Lake Superior stone, granite ledgestone, limestone and river rock
- Natural stone facing on gas fireplaces and wood-burning inserts
- Rumford fireplaces, tall and shallow so they throw more heat into the room
- See-through and three-sided fireplaces for open floor plans
- Cooking fireplaces with forged crane arms, and fireplaces combined with a wood-fired oven
- Outdoor stone fireplaces and outdoor kitchens
- Refacing an existing fireplace in new stone, and rebuilding failed ones
Can you put natural stone on a gas fireplace or insert?
Yes, and it is a big part of what we do. In many homes the gas fireplace or wood-burning insert is installed by a hearth dealer or HVAC contractor, and we come in and finish it in natural stone, from a simple surround to a full floor-to-ceiling stone wall with a hearth and mantel.
However, we do not sell or install the units themselves. Instead, we build the stone around them and follow the clearances in the unit’s own installation manual. As a result, the finished wall looks like it was always there.
Stone facing on a gas fireplace or insert with an 8-foot wall typically runs about $5,000 to $8,000 in stonework, depending on the stone, the hearth and the mantel.
Why natural stone and not manufactured stone?
As a rule, we work in natural stone only. It holds its color, it can be cut, split and shaped to fit, and it carries the weight and character that makes a fireplace the center of a room.
Which stone is right for my fireplace?
In short, stone choice comes down to the look of the house and how the stone is laid. For example, round fieldstone and river rock give a cabin or lake-home look. Split granite and ledgestone read more tailored. Limestone and cut ashlar give crisp lines and clean joints.
Also, local stone is a big part of what we do. Lake Superior stone, Minnesota granite fieldstone and stone gathered from a client’s own land all show up in our work. If you have a pile of rock from clearing your lot, we can often build with it.
How do we build a stone fireplace that actually draws?
A beautiful stone fireplace that smokes into the room is a failed fireplace. What makes a fireplace work is hidden behind the stone: the firebox, the throat and damper, the smoke chamber and the flue.
I think about this the way the old samurai writers thought about rectitude. In Bushido: The Soul of Japan, Inazo Nitobe quotes an earlier writer who called it “the bone that gives firmness and stature.” Bone is not the part anyone admires, yet everything else hangs on it. A fireplace is the same. The stone is what people see. The firebox, smoke chamber and flue are the bone, so we build them as if someone will inspect every joint, even though no one ever will.
A fireplace is simpler than a masonry heater, but it still takes careful planning. Here is how we built one near Eau Claire, Wisconsin: a 36 x 36 inch Rosin fireplace in rustic limestone with a blacksmith-made cast iron cooking arm, in a home loosely based on Frank Lloyd Wright’s architecture.
1. Design and layout of the stone fireplace
First of all, every fireplace starts as a drawing. We lay out the firebox, the block around it, the insulation, the chimney and the stone veneer, so every dimension and clearance is settled before we arrive. By then the foundation is usually in.
2. Build the Rosin firebox by hand
We build the firebox in firebrick and refractory mortar. Its shape is what makes it draw. The sides angle out, the back curves forward, and the throat narrows smoothly into the smoke chamber with no sharp ledges to trip the airflow. As a result, smoke and hot gases follow that curve up and out instead of rolling back into the room, while the curved back throws heat out at floor level.
3. Insulate the whole unit
Next, the entire firebox is wrapped in at least 2 inches of ceramic insulation, with more added as the build goes up. Insulation keeps the firebox hot. Consequently, the fire burns cleaner and drafts harder.
4. Smoke chamber, damper and chimney
Above the firebox goes our Solid Rock stainless steel smoke chamber. It connects to an insulated Class A chimney, sized to the firebox opening, and every masonry fireplace we build is topped with a Lock-Top II damper on top of the chimney or with one of our Solid Rock stainless steel butterfly dampers with a chimney adapter. In addition, this job has a second flue for a fireplace in the basement.
5. Block and steel
Then the concrete block goes up around the firebox and smoke chamber, with a steel lintel over the opening and wall ties set for the stone. That way, the block meets code and carries the weight.
6. The stone fireplace facing
Finally, the stone goes on. Here it is a rustic limestone with a single-stone lintel and a flagstone hearth. In other words, the only part anyone will see is the last thing we do.
When a fireplace we did not build is smoking, the cause is usually one of those hidden parts. Our stone chimney and fireplace restoration guide walks through how we diagnose it.
What does the building code require for a masonry fireplace?
We build to the 2024 International Residential Code (IRC), Chapter 10, and to whatever your local inspector enforces where that is stricter. Minnesota’s current residential code is based on an earlier IRC edition. Meanwhile, Wisconsin uses its own state code. Therefore, the inspector’s code always governs the permit. The main requirements a masonry fireplace has to meet:
- Firebox depth (R1001.6): at least 20 inches deep, with the throat at least 8 inches above the opening. Rumford fireplaces have their own exception: at least 12 inches deep and at least one-third of the opening width. Our hand-built Rosin fireboxes are typically 18 inches deep plus 4-1/2 inches to the face of the opening, about 22-1/2 inches in all before the hearth.
- Firebox walls (R1001.5): 8 inches of solid masonry at the back and sides, including a firebrick lining at least 2 inches thick laid in refractory mortar.
- Damper (R1001.7.1): a ferrous metal damper at least 8 inches above the top of the opening, operable from the room.
- Smoke chamber (R1001.8): solid masonry walls, parged smooth inside with refractory mortar, and no taller than the fireplace opening is wide.
What are the hearth, clearance and chimney rules?
- Hearth and hearth extension (R1001.9 and R1001.10): a 4-inch-thick hearth and a hearth extension at least 2 inches thick, reaching 16 inches in front of and 8 inches past each side of the opening. If the opening is 6 square feet or larger, that grows to 20 inches in front and 12 inches to each side.
- Clearance to combustibles (R1001.11): wood framing kept at least 2 inches from the front and sides of the fireplace and 4 inches from the back. A wood mantel stays at least 6 inches from the opening, with limits on how far it projects within 12 inches.
- Chimney height (R1003.9): at least 3 feet above where it passes through the roof, and at least 2 feet higher than any part of the building within 10 feet.
- Chimney cap (R1003.9.1): a sloped concrete, metal or stone cap with a drip edge and a caulked bond break around the flue liners.
What code applies to a gas fireplace or insert?
Gas fireplaces and factory-built wood units are different. Under R1004 they are installed according to their listing, so when we finish one in stone, the manufacturer’s installation manual sets the clearances and hearth requirements we build to.
What is a Rosin fireplace, and why do we build them?
Most of the masonry fireplaces we build use the PriorFire Rosin style firebox, a curved-back design based on Rosin’s work and developed by Chris Prior of Adirondack Chimney Company in New York. It is his design, not ours. Chris Prior and John Meredith hold U.S. patents on it (US 11,713,882 and US 12,535,217). We build it by hand on site from firebrick and refractory mortar, not from a kit. Unless a client or architect specifies a Rumford, this is the firebox we build.
We build Rosin fireboxes because they are more efficient. A 36 x 36 inch Rosin firebox runs on a 9-inch round flue, about 64 square inches, depending on chimney height. A Rumford with the same 36 x 36 inch opening needs a round flue of about 16 inches, roughly 200 square inches. That is about a third of the flue area. In any open fireplace, most of the fire’s heat goes straight up the chimney, along with warm air pulled from the room. A smaller flue sends far less of both up and out, and that is where much of the Rosin’s efficiency comes from.
Where does the Rosin stone fireplace design come from?
The design comes from Professor Paul Otto Rosin, a German engineer who moved to London in 1936 and studied how combustion gases flow through a fireplace. Using scale models, he refined Count Rumford’s shallow, angled firebox into the shape with the least turbulence. He presented the work to the Institute of Fuel in February 1939 as “The Aerodynamics of Domestic Open Fires”, published that year in the Journal of the Institute of Fuel, Vol. 12.
However, the key difference is the back wall. For instance, a Rumford has a straight fireback. A Rosin back curves forward, with a hump about a quarter of the way up that turns heat out into the room at floor level, where people sit, instead of letting it rise up the chimney. The firebox is shallow with widely splayed sides, so the fire sits close to the room, and the smooth throat carries smoke cleanly up the flue.
What does a Rosin firebox look like inside?
The photos below show the inside of one before any stone goes on. This Prior Fire Rosin firebox, on a job near Bemidji, Minnesota, has its smoke chamber corbeled in firebrick instead of our stainless steel chamber. Either way, it narrows smoothly so the gases keep moving up the flue.
The Luhrsen and Anderson fireplaces in our project list below are both Rosin fireplaces.
What is a Rumford fireplace, and should I build one?
A Rumford fireplace is tall and shallow, with widely angled sides and a streamlined throat. Count Rumford published the design in the 1790s. Even so, it is still one of the best-drawing, best-heating open fireplace designs there is. The Buckley Rumford Company has a good history of the design.
We build a Rumford when a client asks for one or the project calls for it. We also build them with cooking cranes and paired with wood-fired ovens, and we fabricate custom fireplace doors to fit them.
Do you build see-through and three-sided stone fireplaces?
Yes. Above all, a see-through or three-sided fireplace lets one fire serve two rooms or anchor an open floor plan. However, they take more care in design. Because they are open on more than one side, the firebox and smoke chamber have to be built for it.
Do you build outdoor stone fireplaces?
Outdoor fireplaces and outdoor kitchens are a big part of our summer work around Duluth and the lakes. We also build them with the same firebox and chimney detail as an indoor fireplace. In addition, they get caps and flashing that stand up to northern freeze-thaw. We also build simple Scandinavian-style outdoor fireplaces, like the one on the deck at the Scenic Cafe north of Duluth. For steps, pillars and patios around them, see our entryways and outdoor stonework.
Can you reface or restore an existing fireplace?
Yes. For one thing, a dated brick fireplace can be refaced in natural stone, and a failing one can be rebuilt, from a new firebox to a new chimney crown. On older homes, for example, we match the original stone and mortar. That way the repair does not damage the masonry around it. Our masonry restoration page covers that work.
One example: a 1938 granite fireplace from the old Sullivan’s Lodge near the Sucker River. The owners saved and numbered the stones, and we rebuilt the fireplace by hand on their new covered patio with a new firebox and smoke chamber. Lake Superior Magazine wrote about the project.
Should I build a masonry fireplace or a masonry heater?
First of all, an open stone fireplace is mostly about the fire you can see. If your goal is to heat the house, a masonry heater is the most efficient fireplace you can build: a radiant heat storage appliance that burns hot for 2 to 3 hours and releases that heat into the house over 12 to 24 hours.
How efficient is an open stone fireplace?
Not very. Traditional open fireplaces generally run around 10 percent efficient, according to University of Illinois Extension. Canada Mortgage and Housing Corporation’s A Guide to Residential Wood Heating goes further: tests have shown that conventional fireplaces “can actually produce a negative energy efficiency,” because the warm room air they pull up the chimney is replaced by cold outside air.
How efficient is a masonry heater?
A masonry heater, by comparison, is built to burn wood completely and keep the heat. Norbert Senf of Lopez Labs has tested masonry heaters for decades. He puts combustion efficiency at “typically around 96 - 99%” for good masonry heaters. He also calls about 75 percent overall “a very good real world number” (Senf, Short Course on Masonry Heating Systems). The ceiling for any wood appliance that does not condense its exhaust is only about 80 percent. In other words, a good heater gets close to the limit.
Field and lab tests back that up. Natural Resources Canada tested a Heat-Kit masonry heater in an Ottawa-area home. It measured 94.1 percent combustion efficiency and 68.5 percent overall (Zaloum and Senf, NRCan, 2007). At Lopez Labs, a 2019 burn on the Masonry Heater Association research heater reached 99.2 percent combustion efficiency. That same run was 76.2 percent overall (Lopez Labs test results, run MHA-1911).
You still see the fire. A masonry heater always has a glass door, and the firebox can be up to 32 inches wide, so it reads like a fireplace in the room. We build both, and the same stone can face either one.
A heater is often the better buy, too. A big stone masonry heater typically runs around $30,000 to $35,000, while a large all-masonry fireplace starts around $50,000 and averages $80,000 to $90,000. That is why, when someone asks us for a fireplace to heat their home, we usually show them a heater first.
Stone fireplaces we have built
A few of our stone fireplace projects, each with its own write-up:
- Luhrsen Lake Superior stone fireplace, a 23-foot Rosin fireplace in Duluth Township featured in Lake Superior Magazine
- Luikart lodge fireplace, a 1938 granite fireplace from the old Sullivan’s Lodge on the North Shore, rebuilt on the owners’ patio and featured in Lake Superior Magazine
- Zerwas fireplace on Island Lake, north of Duluth, Montana ledgestone facing on a floor-to-ceiling gas fireplace with a built-in firewood niche, featured in Lake Superior Magazine, Volume 42, Issue 6
- Anderson 36 x 36 Rosin fireplace in Montana ledgestone
- Corinthian granite Rosin fireplace on Island Lake
- Rumford fireplace in Superior, WI, a 3 x 3 Rumford in St. Cloud granite with a 12 foot granite mantel and a 1 inch steel hearth
More of our work is in the project gallery.
Stone fireplace questions we hear most
What does a custom stone fireplace cost?
Natural stone facing on a gas fireplace or wood-burning insert, on a typical 8-foot wall, usually runs $5,000 to $8,000. A custom all-masonry stone fireplace usually starts around $50,000. A typical full build runs around $90,000: a 3 x 3 foot Rosin firebox, all masonry, about 25 feet tall with stone inside and out, all the chimney materials, a concrete cap with a metal crown, and a Lock-Top II damper. Every fireplace is priced from a written estimate after we see the site, because the stone, the size of the firebox, the chimney height and the hearth all change the number.
Do you install gas fireplaces and inserts?
No. Your hearth dealer or HVAC contractor installs the gas fireplace or insert, and we finish it in natural stone around it, following the clearances in the unit’s installation manual.
Do you use manufactured stone?
No. We work in natural stone only, including fieldstone, Lake Superior stone, granite, limestone and river rock.
What areas do you build stone fireplaces in?
We build stone fireplaces within about 1.5 hours of Duluth, including Superior, Hermantown, Cloquet, Two Harbors and the North Shore, the Iron Range, and northwest Wisconsin towns such as Cable, Hayward, Minong, Lake Nebagamon and Bayfield.
What kind of stone can you use?
Fieldstone, Lake Superior stone, split granite, granite ledgestone, Wolfeboro granite, limestone, river rock and brick are all in the photos on this page. We also build with stone gathered from your own land.
What is a Rosin fireplace?
A Rosin fireplace has a shallow firebox with a curved back wall, a design Professor Paul O. Rosin developed in the 1930s from Count Rumford’s work. The curve turns more heat out into the room at floor level. It is the firebox we build by hand in most of our masonry fireplaces.
What is a Rumford fireplace?
A Rumford is a tall, shallow fireplace with widely angled sides and a streamlined throat, a design Count Rumford published in the 1790s. The shape reflects more heat into the room and carries smoke up the chimney cleanly.
Can you reface or rebuild my existing fireplace?
Yes. We reface existing fireplaces in new stone and rebuild failing fireboxes, smoke chambers and chimneys. Restoration work is covered in detail on our stone chimney and fireplace restoration page.
Do you build outdoor fireplaces?
Yes. We build outdoor stone fireplaces, outdoor kitchens, cooking fireplaces and fireplace and oven combinations for patios, lake homes and cabins.
Is a fireplace or a masonry heater better for heating a house?
An open fireplace is mainly for the fire you can see. If heating the house is the goal, a masonry heater is the efficient alternative: it is a radiant heat storage appliance that burns hot for 2 to 3 hours and releases that heat over 12 to 24 hours.
Why does my fireplace smoke into the room?
The usual causes are the smoke chamber shape, a flue sized wrong for the firebox opening, a chimney that is too short, or a house too tight to supply makeup air. We diagnose it before quoting a fix.
Talk to a third-generation mason about your fireplace
We also provide fireplace design, consulting and construction drawings for designers and architects, for both PriorFire Rosin and Rumford fireplaces.
Send us a photo of the room, or of the fireplace you have now, and tell us what you want. We will tell you what it takes and give you a written estimate. Contact Solid Rock Masonry, call 218-343-2978, or email eric@solidrockmasonry.com.
