I'm in full swing planning the details of my small stick-built construction project that is set to begin this spring and have now come to the chimney...
My father-in-law plans to build the chimney for us since he can get bricks cheaply and has the expertise. My question now is whether to settle for brick smoke channels or to install double-walled liner pipes from the start. Will the lifespan be increased, or should the lifespan be sufficient with just bricks? Can you have combustible material (wall) closer if you use liner pipes?
We will have a tiled stove, a wood-fired kitchen stove, and a fireplace, with only the tiled stove being used frequently, the fireplace occasionally, and the kitchen stove likely during power outages. Are three smoke channels needed, or could two suffice if done in a certain way?
If you build one shell around and have three liner pipes in it; can the three pipes be tightly against each other, or must there be spacing?
Hope someone has answers to my questions.
My father-in-law plans to build the chimney for us since he can get bricks cheaply and has the expertise. My question now is whether to settle for brick smoke channels or to install double-walled liner pipes from the start. Will the lifespan be increased, or should the lifespan be sufficient with just bricks? Can you have combustible material (wall) closer if you use liner pipes?
We will have a tiled stove, a wood-fired kitchen stove, and a fireplace, with only the tiled stove being used frequently, the fireplace occasionally, and the kitchen stove likely during power outages. Are three smoke channels needed, or could two suffice if done in a certain way?
If you build one shell around and have three liner pipes in it; can the three pipes be tightly against each other, or must there be spacing?
Hope someone has answers to my questions.
Google Leca chimney elements instead of bricks. Easy for your father-in-law to set up.
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The Builder
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The Builder
We have built a Skånelänga, and I have constructed 3 brick chimneys. One in the kitchen, one for the stove, and one for the wood boiler that we use to heat everything. A brick chimney lasts the longest, accumulates heat, and is the easiest to get a draft in. In our cast iron stove, it only takes an A4 paper to light up. The chimney sweep who inspected them was thrilled that a "real" brick chimney wasn't forgotten.
Lecamuraren
Lecamuraren
lecamuraren said:
No. It absolutely does not. Brick chimneys have yet to prove themselves as having the longest durability. On the contrary.
Brick for chimneys (full brick) is a masonry brick that is fired like red brick (at best), i.e., at a lower temperature than yellow. But it can also be a foreign brick of unknown manufacturing, where the clay is poorer in lime. (Even Swedish 'secondary brick' is sometimes sold as chimney brick.)
Red brick is not frost resistant. It therefore often freezes and breaks above the roof.
It is correct that brick stores more heat. This is due to the weight. But it has no check valve and thus releases as much heat and just as quickly. If you measure the temperature at the top and at the smoke inlet, you get a large difference. This causes condensation inside the smoke channel when the chimney cools. The moisture then becomes water that runs down the pipe. Especially in summer. An addition of sulfur from the flue gases causes the brick to corrode from the inside. Therefore, you have to re-line the pipe internally, but it is difficult to get the mortar to adhere to a greasy surface like soot.
If the pipe is built with refractory mortar (joint thickness a few millimeters), it can last longer.
Leca chimneys are not much worse as 'heat storers'. But they are better insulated and therefore do not have as much condensation. The channel is also completely smooth on the inside and well sealed with cement mortar. Joined together, stacked up, and therefore have no joint thickness. There is also a higher 'course height' on the elements (approx. 30 cm) compared to horizontal joints of 80 mm for brick (unless it is 20-/module brick with a course height of 115 mm).
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The Builder
I have built my chimneys the way they were made 100 years ago, the ones that still stand today.
I sourced massive stone from the 1930s, because it doesn't freeze and crack. Bricks from the 1960s and onwards can't be used for a chimney.
The chimney from the wood-burning stove, where I light fires twice a day, never gets cold, so no condensation forms there. Inside the house, the chimney functions as ventilation with constantly rising warm air, so no condensation forms there either.
A classic brick chimney should be soft (flexible), so it's built with lime mortar. Definitely not with refractory mortar, which becomes too hard. In an old house, with a roof truss that can move during a storm, the chimney needs to move with those movements.
Lecamuraren
I sourced massive stone from the 1930s, because it doesn't freeze and crack. Bricks from the 1960s and onwards can't be used for a chimney.
The chimney from the wood-burning stove, where I light fires twice a day, never gets cold, so no condensation forms there. Inside the house, the chimney functions as ventilation with constantly rising warm air, so no condensation forms there either.
A classic brick chimney should be soft (flexible), so it's built with lime mortar. Definitely not with refractory mortar, which becomes too hard. In an old house, with a roof truss that can move during a storm, the chimney needs to move with those movements.
Lecamuraren
lecamuraren said:
I must object to three of your claims.
"I picked out solid stone from the 1930s, because it doesn't freeze and crack."
It can indeed freeze and crack. It's not about the age of the brick, but how the brick is made and fired.
Freezing risk in brick only exists where there is water left in the stone. Water can be encapsulated in two ways: centrally in the middle or in the outer layer.
Brick in the past (green brick before firing) was hand-molded in form. Therefore, it wasn't particularly homogeneous. It was then air-dried outside initially on the ground in the sunshine and could therefore contain water in the middle. It was later stacked on 'rin' (wooden lath) for further drying under cover with a roof.
Modern brick is machine-made in a continuous extrusion process. As a result, it is always homogeneous. It's dried in a kiln, which reduces crack formation. Water usually remains in the outer layer but evaporates mostly during cooling before being stacked on tunnel kiln carts.
"Bricks from the 1960s onwards, can't be used for a chimney."
Again, it's not about the age but whether it is whole bricks, how it is fired, and where in the kiln it was located.
The firing is associated with how the kiln was designed at different times. Earlier (1930) there were kilns (beehive kilns) that were 'loaded' with bricks (stacked inside, closed, heated up, opened, bricks taken out, all by hand). Bricks in the middle of the kiln were therefore less hardened than those on the outer ends since the entire kiln was almost completely filled with numerous cubic meters of bricks. However, since no person could go inside and remove the burnt bricks until the kiln had cooled sufficiently, heat equalization occurred so that even the stones inside were better burned but not as hard as the outer ones.
In later kilns (tunnel kilns), bricks are placed on carts (holding fewer bricks/piece than a beehive kiln) that pass through the kiln, slowly passing several burners in the kiln's sides and roof until the carts come out the other end. The bricks then stand and cool before being transferred to pallets. The outer heat thus doesn't fully affect the interior bricks. Hence, outer bricks are harder fired than those in the center of the cart.
The difference is that temperature in a beehive kiln cannot be monitored as precisely as in a tunnel kiln. The outer layer can, therefore, be so hard that bricks have substantial cracks, while those in the middle barely reach their proper firing temperature. As a result, incompletely fired bricks might have undergone a second firing.
In the tunnel kiln, temperature can be controlled and adjusted in two ways: by increasing the heat or slowing down or speeding up the carts. Therefore, the firing is more homogeneous, scrap rates for exterior bricks are lower, and color (on facing bricks) more uniform. Additionally, capacity was increased. All manual work (loading/unloading) takes place outside the kiln.
The fact that firing temperature can be precisely controlled from the outside means brick from a tunnel kiln has better properties than those from a beehive kiln. If the brick is over-fired, it becomes brittle and rings like glass when struck. It's completely unsuitable for bricklaying. It's possible to do, but there is a significant risk of cracking if exposed to more heat. Therefore, it's entirely unsuitable to build chimneys with.
"A classic brick chimney should be soft (flexible), so it's mortared with lime mortar. Absolutely not with refractory mortar, which becomes too hard. In an old house, with a roof truss that can move during a storm, the chimney must follow the movements."
Not even tall factory chimneys of 25 meters or more are particularly flexible at the top. But they bend due to wind power causing cracks in the joints. It doesn't matter if it's built with K-mortar or KC-mortar. The mortar is not elastic.
Chimneys for smaller houses are not exposed to wind forces in the same way and therefore do not need to be (and should not be) flexible. If the roof truss moves due to the wind, it does not affect the chimney unless improperly constructed. According to building codes (from 1944 onward), there should be an air gap of 50 mm around the chimney as fire protection. No combustible part of the roof truss may be closer than 50 mm from the outside of the chimney, and such movements in the roof truss do not exist in a low house unless it is very poorly constructed. The roof panel, however, may be in direct contact with the chimney's exterior. It can hardly affect the chimney's vertical alignment more than the last meter. Therefore, no reason in an old house to build a new chimney with lime mortar to make it flexible. If the chimney is exposed to bending force, the fire risk increases as sparks can escape through the cracked joints and ignite the roof truss.
Regarding refractory mortar, it's hardly suitable for use further from the hearth than one (1) meter. Already there, the temperature has dropped below the temperature (about 1100 degrees C) at which the brick is fired. If the brick is made of limestone-rich clay (yellow brick), the firing temperature is a bit higher (between 1200-1300 degrees C). (And even better frost protected.)
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Byggaren
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