Brick Layout

I've been reviewing the RMH layouts for quite some time.  
I have a decent supply of IFBs and I wondered if there is any advantage to laying them as stretchers vs shiners in the firebox.  
Also, instead of getting slabs for the ceiling, should (or can) I consider corbelling with the k28 IFBs?

Thanks to all.

Hi Randy;
Common rmh construction has been using shiners.   (Bricks stood on the long narrow side with the broad face exposed.)
I see no reason you could not lay them as stretchers, were you thinking soldier or sailor pattern? (Bricks laid flat with narrow side exposed)

For a long while, I thought batch boxes needed a flat roof.
Recently Peter said they do not.
So, I see no reason not to corbel the roof.

Be sure to take lots of pictures to share your build with us.

Thomas - Thank you so much for the quick reply.  

I am thinking along the lines of running bond stretcher.  I just wasn't sure if I would gain any efficiency (thicker wall = more heat retention?) or using few bricks (shiner/ on edge) was better for brick bell surround.

And if I understand it right, corbelling should be a third brick per course.

I plan to dry lay as much of the heater as I can - outdoors first.  Don't want to test fire it first try in the house.  But I won't be trying to mock up the 30' chimney that it will hook to in it's final position!

As far as pics, I'm going to try to work with a photographer buddy to set up time lapse for the real build.

Hey Randy;
Is the core itself completely inside the bell? I'm assuming it is.
Were you planning on using a mortar on the core?
Or were you thinking of dry stacking and making an external frame?
If your bell has the room and you have ample IFB then I think that a stretcher pattern might make a more stable assembly.

The bell bricks are best laid flat and mortared with clay or grout.

I have never corbeled a roof yet so I can't help you there.

Use some kind of chimney on your mockup or it will have draft issues.

A time-lapse build video will be awesome!

Yes, core will be entirely within the bell

I was hoping to go dry stack core with angle iron frame, octagonal riser

My thought is to build this just once - but I expect I should go with clay for bell assembly so I could, if necessary, make repairs

Guess I'll have to get some pipe for a temporary stack.

Plan calls for firebox 20" off the cellar floor, the riser will be as high as I can make it and topped with a white oven in the peak of the bell - on the main floor.

Measurement from base to bell top will be just about 8 feet.  Top of white oven bell will be standard counter height.

Man, I'm really glad I know an awesome photographer - and he's fascinated with the project!

I have corbeled a 6 1/2" batch box roof and a couple of bell roofs. The firebox will be easy if you lay the bricks flat and perpendicular to the wall, reaching 1/3 to 1/2 of a brick length in from each side. Unless you have a huge system, a single firebrick length can then span across those corbeled bricks.

For bells, the method of corbeling depends on the configuration of the walls. On a 26" square (inside) bell, I was able to lay out a corbel pattern with three steps of corbeling to reach the flat ceiling bricks. In the mockup on the floor, this pattern was fully self-stable without mortar. A larger version would be possible, but with more steps and less internally stable.

thomas rubino wrote:Hi Randy;
Common rmh construction has been using shiners.   (Bricks stood on the long narrow side with the broad face exposed.)
I see no reason you could not lay them as stretchers, were you thinking soldier or sailor pattern? (Bricks laid flat with narrow side exposed)

For a long while, I thought batch boxes needed a flat roof.
Recently Peter said they do not.
So, I see no reason not to corbel the roof.

Be sure to take lots of pictures to share your build with us.

There is a lot to this thread that I apparently don't understand the terms. I will list and comment but certainly will enjoy return comments:
1)  If bricks stood on the long narrow side,  then wouldn't the long narrow side be exposed? to the heat,  If you lay  flat, then the flat wide side would be exposed? ( much less bricks, but maybe the whole point was a thick bell top?
2) Perhaps I have always mis understood "corbel"  as I always thought that meant to Lay out from a vertical structure, but I am presuming we are meaning to lay in towards the center.  Is there a maximum  IN per layer?  Can this be done without a supporting structure? Even if it would take 2' or more to close in?
3) Perhaps I read this wrong, but at the top of the bell, we don't want Insulated fire brick? do we?  I think Peter always said from the top of the riser to the top of the bell should be fire brick as well.  Please correct if I am thinking wrong, as my standard bricks cost me $0.10 each and my fire brick about $1.25 each, so a pretty big difference.
4) Somewhere in here, I think the original poster said " I am going to make the riser as high as possible"  I always thought that was pretty important to follow the % HEIGHT of Riser- thus specked for each size of stove,  i.e. 5, 6 or all the way up to 10"

As you can see, I was not aware we could stray very dramatically from the specs for a given size stove, including the Inner Surface Area, of a single bell.

Inquiring minds want to know.

Hi Scott, thanks for the questions (I always like it when folks make me think through my process again - I kinda hope it helps me screw up less!)

As for the  Brick Layout , I just googled it.

Don't know if I used "corbelled" properly - I assumed it means shifting the bricks either in or out - like the decorative stuff at the top of many chimneys.

I think that the top of the bell has to be firebrick - it should be the hottest except for the riser itself.

Some time back, I contacted Peter about a maximum space between the top of the riser and the cap of the bell.  He had tested and found a minimum, but never found any upper limit.  Granted, he stopped somewhere but there didn't seem to be any practical maximum.  If that is the case, I can't see how going to 11xBase for riser height should be a problem (Peter's calcs recommend 8 to 10 times).

My reason for the extra tall bell is to keep the firebox on the lower level and the white oven at the apex of bell #1 in the kitchen on the main floor.

Corbels stick out from the wall below - inside or outside of an enclosure makes no difference. If you offset the bricks so they step in on one side and out on the other, they are "corbeled" on the overhanging side. I don't know of a specialized term for the step in on the other side.

Every orientation of a brick in a wall has a specialized name, as shown here.

Generally, the top third to half of the interior of a bell with a firebox riser in it needs to be firebrick. The International Building Code for masonry heaters requires all internal bell or flue channel surfaces to be firebrick. This is not related to the actual batch box riser height; there can be an effectively unlimited maximum spacing between top of riser and top of bell, but the riser should stick fairly close to the recommendations. Bell total internal surface area needs to stick close to the recommendations.

in a rectangular bell, you can corbel in pretty much as far as you want, like a dome, but there comes a point where there is thrust outward that will destabilize the walls below unless they are securely braced. A long bell with straight walls and more than around 16" internal width would need bracing every couple feet or so, as the corners of the structure are too distant to brace the corbeling.

Note that long stretches of repeated corbeling of a whole wall will become unstable, depending entirely on the strength of the mortar to stay intact. A corbeled opening in a solid wall can be much larger, since the rest of the bricks in the wall keep the corbeled bricks from sliding outward or falling down. Larger spans of a long bell will need to be vaulted rather than corbeled, so all the bricks have their joints oriented toward the center of the arch and in full compression rather than depending on friction to keep them from sliding outward.

You can increase the stability of corbeling by adding wall structure above the corbel layer; this is done in a similar manner in Gothic cathedrals, where the flying buttresses have tall heavy spires above the springing of the arch. This keeps the average or combined thrust more down than sideways so the buttress is not pushed over by the arch.