Masonary heater on timber framing with oven and cooktop?

If you haven't finished your bowl of popcorn yet and are looking for an excuse to munch on a few more morsels of savory corn puffs then I have a video for your entertainment...

I'm planning to take a crack at making a masonry heater for a small 230 sqft wood frame apartment. It's for the "second story" where the total available height for both floors is 14' so the first and second floors will be 6'11" and 6'3" respectively. Good for a shorty like me but a noggin bumper for those of you that were blessed with a more active tall gene. I've never built a rocket mass heater or a masonry heater so this could end up being just a learning experience but I figure there are worse things in life than learning through some trial and error. Who knows maybe it'll even work with versions 2, 3, 4...?

By uploading, the hope is that obvious problem(s) to an experienced person might be pointed out and fixed before the first version is constructed.  

I'm also hoping that some pointers will lead to a better masonry heater for other people's future projects and maybe encourage more of us that want to get in there and make something with our hands. Even if it doesn't work the first time

Thanks for posting such a complete plan for the experts here to look at!  This really helps for those that can give you detailed advice.

My input is this:  you're building your combustion chamber on a steel plate base covered with just under 2" of fire brick. While this will keep your wooden floor from turning into charcoal, you may find that just under 2" of fire brick on top of a steel plate will leak too much heat.

My own plan on a wooden floor had to be revised to include a metal plate....since I didn't have much overhead to raise the barrel, I used just a steel plate (know it would oxidize out) at the bottom of my J tube.  What I found to my surprise is that my steel plate leaked too much heat and the top of my barrel temperature dropped 100F.

....so while you're not burning directly on a steel plate, you may find your max temp would be different or higher if you used a thicker layer of insulating firebrick (yes, there is firebrick which is designed not to insulate but to transmit heat), on top of your steel plate.

...I maybe mistaken, Donkey has methods of checking this but he may not be interested in your particular design.

I make no comment on the rest of the design, I prefer the rocket mass heater and tend to put blinders on when it comes to other designs the permies community hasn't tested.  I would suggest you build your burn chamber outside and test it before mortaring it into place. You'll be able to make changes this way if you're not content with the highest temp. If you can't get your burn chamber to fire correctly, you can reconsider the base design too.

good luck!

Very clever video!
I am only just trying to get my head around these riser less deigns so I can’t say how well your design will work but it sure looks good.

Hi Glen,  As mentioned, the wooden floor is an area that needs to be protected well as its not something that can be fixed without an entire teardown. Providing air flow has always been suggested when dealing with wooden floors. A few links regarding this:

Materials-Free-Standing-Wood-Stove
perlite-RMH-cob-bench

This video shows the air channels briefly on a build over a wooden floor. Check out the other clips on this build too. Very nice!
RMH 1 Intro from the DVD Rocket Mass Heaters with Ernie and Erica

I agree Fox, the riserless core is a bit of a head scratcher for me too!

Also, the base of the stove (the wood storage area) can probably be just the same brick your using for the bell as it won't experience any real high temperatures.

The firebox dimensions 9" x 5.25". Seems rather narrow. Are you going off another design?
Looks somewhat like the DSR 2 but with a sidewinder twist with no port. Not sure how the afterburn or secondary air is utilized in your design.

I'm assuming the core is made out of insulated firebrick?

The space where the exhaust comes out of the firebox and hits the bottom of the oven seems cramped and that it may be a high friction area.
Just not sure how the stove will draft properly before it even gets into the second bench bell.

There is a lot of elements here that I don't have direct experience with but just going with similar experiences that may apply so take what I say with a grain of salt. I love to experiment too and stretching boundaries is a part of it.

Definitely keep us posted if this makes its way into production!

Hi Orin,
Thanks for taking a look and for the suggestion. I'll take your advice and increase the burn floor thickness from 1” to 2.5”. Makes sense to me and it doesn't seem like it could hurt to do so.


Hi Gerry,
Thanks for the link to Ernie and Erica's video intro. That's very helpful to see how they vented under the mass and stove. It might be a challenge for me to do the same with this bell housing meanwhile keeping the bench at a comfortable height to sit on. I'll tinker with the plans.

I'm not following a design in particular and at the same time yeah, I'm trying to follow what seems to work well with what others have done. I went with 9” x 5.25” (47.25sqin) since the square area is somewhere in between a 6” and 8”. Mr. Walker of WalkerStoves has some beautiful low rise stoves and his stoves are an inspiration. He has much, much more experience than I do so I've just resolved to learn as I go. Worse comes to worse I can give up and someone local might get some bricks on the cheap.

“Not sure how the afterburn or secondary air is utilized in your design. “ That's a good question. I was planning on adding in secondary air with some rectangular steel tube welded into an L shape but I accidentally deleted that part of the design somewhere along the many versions of the stove. I just forgot about it and never added it back in. I'm pretty sure that a secondary air supply is going to be critical to get a clean burn so I'll see if I can figure out a way to add it back in.

Yep, the core is firebrick for the floor and the walls of the burn tunnel. The roof of the burn tunnel is Ceramic Fiber Insulation Board.

“Just not sure how the stove will draft properly before it even gets into the second bench bell.”  My wager is that the 14' rise within the flue will pull the air into the burn tunnel. So unlike a rocket stove where the low pressure and draft is created by the nearby riser, this one will be pulling from much further away in the chimney.

Glen Yoshida wrote:Worse comes to worse I can give up and someone local might get some bricks on the cheap.

If it ever gets to that point, instead of scraping the whole project altogether, have you considered building something that is a lot simpler (and maybe smaller) in design like a basic J tube, get a season or so of experience with that, then if still so inclined move to a more advanced build?

From your video, I can see your Sketchup skills are very good, but I don't know your build skills so its hard to know whether to encourage you down a path that's going to be long and probably full of unexpected results or full of joy and happiness even if it all goes south. Of course its your decision, but a good time to do this rather than later as you've mentioned. Either way, lots of good people here willing to help out in whatever way we can....or at least to watch your build and learn from you!