Part 1: Masonry Heater

Added: 2026-05-11

[00:00:01]About 3 years ago, my parents' house burned down from an electrical fire.

[00:00:06]And they've been on this land for 30 years. They're totally committed to this land and to their homestead here.

[00:00:13]So, for them, there was no question about whether they wanted to move. They knew that they wanted to rebuild right here in the same spot.

[00:00:22]So, over the next 18 months, my family and I rebuilt their house.

[00:00:27]But, something that my parents were saying as their old house was burning down was, "Well, the rebuild will give us an opportunity to have a masonry heater in the new house."

[00:00:40]Now, we're not very familiar with masonry heaters here in the US, but they're very common in Europe.

[00:00:47]And especially in the northern European climates, almost everybody is going to have one.

[00:00:54]There are a number of benefits to masonry heaters compared to like an American metal wood burning stove.

[00:01:02]They're safer, they're some people say about 50% more efficient with their fuel use, and they actually put out a lot less exhaust gases. There's less CO, CO2.

[00:01:16]So, they're better in many ways.

[00:01:19]But, they're they are significant investment and they're very large.

[00:01:25]And so, where I'm sitting right now, we have a 8-in concrete slab that we built into the new house. It's supported by a big brick structure underneath me.

[00:01:37]And that's going to hold up the masonry heater that's going into this house.

[00:01:41]Now, there aren't very many of them here in the US. There are a handful of builders who make these, but fortunately, we happen to have a friend in Germany who has been building these for 30 years.

[00:01:55]Um he works mostly in Germany and Italy, but he has a ton of experience building these. So, we reached out to him and he has been just wonderful to work with. But, >> [clears throat] >> he was good enough to design a masonry heater for this house.

[00:02:13]So, that's what we're going to be working on now.

[00:02:18]So, this is an image from the masonry heater that we're going to be building, the computer model.

[00:02:23]And you can see there's a lot going on.

[00:02:25]So, right here is the main firebox that's going to power the heating side of this masonry heater. And so, there's going to be a large, very hot fire that burns in here.

[00:02:37]This entire masonry mass. And then that's going to go back through the main body of this heater, and there are a bunch of convoluted flues. And the flue gases run through those before exiting the chimney, which is right up here.

[00:02:52]The idea with a masonry heater is that you're burning a very hot fire, which is a a more efficient fire, but then you're also catching the majority of that heat. So, where we're often with metal stoves letting a lot of that heat escape up the chimney, these run it through a much longer, more convoluted set of flues that then trap much of that warmth, and it's retained inside the masonry mass, which then slowly emits it out into the room.

[00:03:25]The other side of this heater is the kitchen side. And so, over here, much smaller firebox, less efficient fire, but this is only going to be fired sometimes.

[00:03:38]Because this fire is less efficient, there's going to be more ash. It's going to be more like a normal wood burning stove that we're used to here.

[00:03:46]And so, we actually have an ash cleanout for this one modeled in.

[00:03:50]Then, there's a metal cooktop, like a little mini wood fired range right here.

[00:03:57]And that's going to be powered by this firebox.

[00:04:00]Then at that point, the flue gases run back through here into the masonry and power a little bake oven up here.

[00:04:08]Then they those, rather than going through the same convoluted flues, almost immediately exit through their own flue.

[00:04:19]Almost immediately exit through their own chimney flue, which is right up here. So, there are two separate flues that we've piped into the house. We've got an 8-in for the main heater side, and then a 6-in for the small kitchen side.

[00:04:34]This heater firebox, as I said, is it burns much hotter. Um typical operating temperatures for these masonry heaters are in the 12 to 1600 range.

[00:04:45]Compare that to an American wood stove where you're looking at more like 7 to 800°.

[00:04:51]Hence the much more efficient burn and the need for all of this masonry massing to absorb that really intense heat.

[00:05:00]Um an off a an add-on that's often added to these is that the flue gases will run to a bake oven.

[00:05:09]And so, here on this side, before they run through their convoluted flues, right away, the heat most of that heat is going up and powering this big bake oven, which should be suitable for bread, pizzas, and then slow cooking, too. Like you could put a cast iron Dutch oven in there and cook a roast.

[00:05:35]This side view shows the bake oven and then also shows some of the masonry detailing that's going on in the back.

[00:05:43]So, those flues run from that combustion chamber, up, power this oven, and then run down through here, and there are actually two sets stacked on top of each other before they pop out over here, and come up through a chimney, which then exits up on top.

[00:06:00]This is a bench on the back side, on the living room side. This is going to be warmed by the flue gases.

[00:06:07]Now, sometimes people run the flues all the way through the bench, and our friend suggested that we not do that.

[00:06:14]That instead, we allow conduction to warm the back of the bench, and then also to some extent, the seat. But, he said in his experience, the seats often get too hot if they are directly powered by the flues.

[00:06:30]Now, we have the other side view showing the kitchen range, and again, the masonry detailing and how it's massed out.

[00:06:41]And then this is starting to get into some of the schematics of the interior core. And so, all of this is the firebrick. These are the long convoluted flues, the red lines indicate changes in level. So, each one is a separate set of flues before they come up and exit.

[00:07:01]So, what we are going to start on today is building up a masonry base on top of the rough concrete that we have in place.

[00:07:09]And our friend suggested that for that, we could just use old bricks that we had lying around. None of this at this stage needs to be refractory mortar because it's not going to come in contact with the intense heat and the smoke of the heater.

[00:07:26]We had hundreds of old firebrick left over from demoing the old house when we tore it down.

[00:07:32]So, we're going to use those bricks to build up the base before we start with the new firebrick and the refractory mortar.

[00:07:39]So, in order to find out how many I need, I'm going to space them out with the mortar joint that I want, and then based on those dimensions, I'm going to generate a number for the entire base.

[00:07:53]So, I'm calculating that for this base, I'm going to need about 252 brick, plus or minus a few.

[00:08:00]So, we're going to go ahead and get some mortar.

[00:08:03]Now, at this stage, because nothing is going to be exposed to the intense heat of the heater or to the flue gases, we're able to just use a conventional mortar.

[00:08:13]So, normally I would mix it myself.

[00:08:16]Today, we're just going to get something off the shelf from a box store.

[00:08:21]So, I'll probably use a type S mortar. I like the Amerimix brand, and we'll get these laid up.

[00:08:30]So, we're now ready to actually start laying brick.

[00:08:33]So, I've put in a 1/2-in OSB spacer along the edge, and this is just to maintain an expansion joint for the wood floor.

[00:08:41]So, that's going to come out later when all the brick is in.

[00:08:45]Uh I'm going to be putting these brick in on edge rather than in the flat because that brings it up to the height we need for this heater base.

[00:08:55]So, I've got a mortar board set up and wet it down, bucket of water, mortar's mixed up, and then a stack of cleaned bricks. We went ahead and brushed them off, which I wouldn't normally do, but here I think it's going to be good.

[00:09:10]And then I also have a knee board. If you have a piece of rigid foam lying around, this will really help save your knees when you're doing work down low.