carol othdac

So sand/clay has no adhesion. This is what I found out. Had not read that anywhere in years of searching these topics. I was working under the assumption that the $50 bag or fireclay was a moderate version of refractory cement, when in reality, the free clay in the yard would likely have performed similarly.

The other realization that compounded my problem, is that the stability was further compromised by laying all the bricks on edge/soldier style. That is rickety. I did that because I want to keep the heater narrow and as small as possible because it is a small work space. Also the reason I'd like some rigidity to it as it will likely take a hit from a stray piece of lumber etc. So it sounds like I can get some refractory cement and use it alone? and no need for sand/clay as their properties may likely be negated entirely once the cement is used?

I'd  like to get confirmation on that point because if sand'clay still do something, I'd use them, as they are paid for and on site....additionally I was planning and still will double up the bricks on the feed and burn tunnel regardless...thanks

regarding mortar mixes. Searching has not revealed much about this; but the idea of mixing in a portion of high temp cement with a mix is the idea I am considering.

Maybe a 1:1: 1 sand/fireclay/refractory cement

There may be a good reason why I havent discovered much of anything on such a mortar (such as the possibility that adding any percentage of high temp cement into the mix negates the flexibilty or other qualities of the sand/clay ?)....., but perhaps it just hasn't been tried. But if you'all have ideas as to why that may or may not work, I'd be interested in hearing, so that I don't waste too much $ and time on high temp cement additives, but if it is a possible idea, it may be worth the risk.

so that is laying them 'on edge'. Which is how I originally built it and how i was planning to rebuild it.

I still need to find out why high temp cement is not viable. If it is because it cracks, why is that a dealbreaker since that is not much worse than a dry stack at that point, plus the leaks are still contained within the insulation and/or the bell. So the piece of mind of having a factor of strength to the core may be worth the potential cracks. This is my current assumption. If that proves to be innacurate and there is no other menthod/mortar, then I will have to refine the sand/clay method as outlined in the early post of mine regarding ratio, sifting sand, temp etc

I have a thread started for the build, but I took it apart to redo later. But i've dry stacked to test various cores with minimal smoking and realize that not much strength is needed if the idea is just to create a burn tunnel and riser that keeps most of the smoke out....but shouldn't a core do more than that? or is that delicateness an inherent part of all cores?

plus, the bricks have been used and have some wear and tear, so are not pristine. I will need some good mortar solution for those parts if nothing else. Plus I'd like some inherent stiffness/structure for at least the burn box and tunnel, as this may end up as a single skin with no protective outer shell.

i let it sit for 3 days and when i went to finish the top section of the riser it just came apart...it was 30-40 degrees for these days. that is the only reason i can think? but i've never used this 'mortar' so dont know if the sand was wrong or what? but in general it seems like a precarious mortar  and i dont know how others get it to work.

the joints where 3/16" 'ish  or smaller, and the sand I used was general construction sand with silica. I knew quickly it had larger sized particles in it than desired and if i try again, it will be sifted finer...the clay was commercial fireclay

maybe if I build it in 50+ temps, sift the sand, and use a 1:1 or 2:1 ratio resulting in less joint size, I could get it to 'work'. Meaning maybe it would hold together while I wrap it with insulation and then when the bell is built over it, the strength of teh core is not an issue? as it will never be 'touched' ? that is the only thing I can think as to how people get it to work. The core must be precarious by nature and the next outer layer of brick is what protects it?  but no one ever seems to mention this? unless im missing something....

recently tried to mortar together a  core with firebrick and 3:1 sand:fireclay with no success. It fell right apart.  In any case, got me wondering about ceramic cores. Have been looking into masonry heaters for 20 yrs and only recently began a first RMH build. Chose firebrick and the mortar that is light and allows for expansion/contraction. Almost all other research on more stiff mortars such as high temp cement etc seem to be passed over because they crack. Correct me if this is incorrect, as I'd like to use this as a solution to my build.  But it started me thinking that these RMH are possibly run too hot and is why they crack? the high temp refractory cements are rated for 2000F and yet they seem insufficient?  Is the switch to ceramic cores a solution to this high temp RMH? and is another solution to run them a bit less 'efficiently', maybe with less insulation around the cores, so that high temp cement is a viable solution?

or is there other info that I have not come across as a good mortar for brick builds?

thank you. The sand I have is 'construction sand with silica'. It seems course to me. So wonder if I can do a 2 to 1 ratio instead so that it is a little more mangageble and might even stick a bit compared to 3 to 1....is 2 to 1 enough to still allow for contraction expansion. If in fact that is the purpose/benefit of the sand?

hello. I am starting a small heater and have fireclay and builders sand(it has some silica).  Also have some basic builders cement.

Just laid the foundation layer of firebrick with 3 to 1 of the sand to fireclay and it went well. But in working with it, it doesnt seem like it would be an ideal mortar for the rest of the build . Due to it not having much 'adhesion and leaves a larger mortar line than ideal I suspect.

So, am wondering if I can alter the mortar for the other TWO parts. I see the burn tunnel and heat riser as the Hot portion and would settle on one mix, and the later ends of the bell and bench the cooler portion with a potentially different mix

After searches and thinking the best idea I have is
for the hot portion:
1- either straight fireclay (slip or thicker variation of a slip)
2- a 1 to 1 of sand to fireclay (the thinking is the sand helps with expantion and contraction?)
3-a 1 to 1 to 1 of sand to fireclay to cement (the thinking here is a bit of 'glue'/cement would help the tall riser hold together but still allow for some dissasembly later?

for the cool portion:
1- 1 to 1 of cement to sand
2- 1 to 1 of cement to fireclay
3- 1 to 1 to 1 of cement/fireclay/sand


or should the basic 3 to1 or 2 to 1 sand to fireclay just be used throughout?


Any ideas as to which (if any of these mixes would work?  thanks much

i see. 6x6 or some suggest adding another 1.5  (7.5) by laying a layer of brick on their face to accomodate for ash buildup but Im not certain on that or if I have enough fire bricks.  Also, I now see the horizontal burn tunnel is much shorter than I was thinking, as its measure of 18" includes the 6" inside the burn tower.

Today got the fireclay, sand, and some ceramic fiber. So am comfortable to start with that diagram. Will put a 3 to 1 mix of sand to fierclay as the minimal insulation layer on the concrete slab, then a layer of firebricks as the floor, and then build up and wrap the riser with ceramic, and the short horizontal tunnel top and sides. Thanks for all the help. The material cost for this little heater is around $650 if anyone is wondering. More than I thought it would be but then again, everything is 2 to 3x the cost these days.

firebrick $375
clay brick $100
fireclay 50 lb $50
Sand $25
Ceramic $50
Stove pipe $50

temperatures these days are around 40-50 F during the day and 25-30 at night. From searches, concrete is barely able to set at 40 but I dont know about sand/fireclay. Would like to build this now as opposed to spring however so am hoping that mix sets up. The natural temp in this little shop probably adds another 5-15 degrees from sun absorption as well during the day but that disappears at night.

the current cost of vermiculite and ceramic insulation is skyhigh like everything. I havent found any cheap insulation options yet..