This post is all about tips and tricks to creating a stellar masonry heater design.
We built our first masonry heater two years ago in the middle of winter (smart, I know.) We built it out of four 55 gallon steel drums in our 300 square foot tiny home. When we first fired it up it didn’t work. We figured out why and tried again, it worked better, but not great. We fixed that problem and another came up. Two years later and we are STILL perfecting our heater. Affectionately known as Mount Vesuvius, our masonry heater is still far from perfect, but we have learned a lot from building it. Here we have included the top tips we wish we had known when designing our masonry heater.
Quick Navigation
- Tip #1 Location, Location, Location
- Tip #2 Know Your Fuel
- Tip #3 Masonry Heater Design is Technical
- Tip #4 Correct Masonry Thickness
- Tip #5 Do Your Research
tip #1: LOCATION, LOCATION, LOCATION
Masonry heaters are almost permanent and aren’t cheap to move. Before you build one it is wise to spend considerable time thinking about where you are going to put it. Think on it for multiple days and consider it from all angles. Where are you going to put it? How will traffic and activity flow around this heater? (It is better to have your heater where you can utilize all that heat radiating out, usually the middle of the room/house.) DO you want to utilize it as a cooking surface or for any other purpose? Where is your chimney going to exit? How tall is your room? Is your masonry heater on the ground floor? If it is on the second story will you need to reinforce the floor? How large of a space are you trying to heat? Taller tends to be better with masonry heaters, how tall are you going to make it? Where are you storing fuel for your stove, where will you be bringing it in from? These are all good questions to think about when considering location.
Tip #2 : Know your Fuel
As part of your masonry heater design it is important that you know what kind of wood you will be burning, how often you will be reloading your heater, where you will get it and how you will store it.
At first with our masonry heater, I was unaware that you don’t load it like another wood stove. You load it in batches or charges. So instead of adding one piece of wood every hour, you will add six pieces of wood every six hours. It is important to decide how often you want to reload your stove and how long in between charges you want to go.
The kind of wood you are using will inform your loading frequency decision. Not all wood is created equal. Certain varieties have more energy, more heating capacity, more BTU’s per pound. This means that you can load the same weight of two different kinds of wood and get different amounts of heat. When you are planning your heater it is important to know what kind of wood you will be burning, as this will effect the dimensions of your firebox, chimney, and air intakes. There are wonderful resources online that cover the specifics of what woods have what BTUs. Here is a resource that I have found, but I would cross reference with others, as they all have something slightly different to say about it.
YOU NEED DRY WOOD. DRY SEASONED WOOD. This was the first mistake we made with our masonry heater. If you don’t have good fuel, your masonry heater will be more temperamental to run and won’t work as well as it would with dry seasoned wood. As part of your masonry heater design think of where you will find wood and where you will store wood.
Tip #3: Masonry Heater Design is Technical
If your like me you have a tendency to eyeball and guesstimate things. Your masonry heater design should not one of them. Calculate specifically how much wood and what kind of wood you plan on burning, in weight and in BTUs. Calculate specifically how long to you want your stove to run and how much space you want it to heat.
There is also a specific ratio of the weight of your fuel to the size of your fire box. For example the dimensions of your firebox are proportionate to how many kilograms of wood you intend to burn at one time. Take the charge weight in kilograms and times it by 900. That number is the number of square centimeters that the surface area of the floor, walls, and roof of your firebox, disregarding all doors and vents. So if you have 10 kilograms of wood and times that by 900 is 9,000. So the surface area of your firebox needs to be 9,000 square cm. That would mean your box would be a cube that is about 39 cm tall wide and deep. While you are running those calculations bear in mind that the area of the floor of your masonry heater must be at least 100 square centimeters per kilogram of wood.
Your air intake also has to be a certain size. It needs to be 10-12 sq cm per kilogram of wood. So for 10 kg of wood the area of the air intake needs to be 100-120 sq cm.
Do your research and don’t skip over the technical stuff, it’s important.
tip #4: Correct MASONRY Thickness
As part of your masonry heater design you will want to be intentional about the thickness of your masonry. If you want your heater to store heat for a long time, it needs to be thicker, but realize with it being thicker it will take longer to heat up. The heat will be a more mellow heat through a thicker surface. A thinner surface will heat up faster, will reach a higher surface temperature, but it doesn’t maintain heat for longer time.
Tip #5: Do your research
Before building your heater and as part of your masonry heater design phase, study up. They are pretty much permanent and when you take them out it isn’t easy. Take the time to do in depth research. Masonry Heaters: Designing, Building and Living with a Piece of the Sun, by Ken Matesz is great resource as is The Book of Masonry Stoves: Rediscovering an Old Way of Warming, by David Lyle. Rocket Mass Heaters: Supereffiecent Wood Stoves You Can Build, by Ianto Evans is also a must read. You can also check out our homesteading resource page for more resources.
Tips FOr Masonry Heater Design Conclusion
There you have it: 5 Tips for masonry heater design! My hope is that this will help you in creating your stellar masonry heater design.
Check out the homesteading resource page for more awesome books and resources on homesteading!