I’m looking to build a large brick smoker/grill unit soon. It will contain an area for burning down the wood into coals, as well. As I’ve checked with some BBQ websites to explore the topic, it has come to my attention that one doesn’t just use regular mortar when dealing with intense heat. It was stated by one man that Portland cement should be used in conjuction with a type of clay compound findable at the local brickyard in order to prevent “exploding” upon first fire. Now I’ve seen cracked units before and have noted that heat must have been the cause, but “exploding” seemed like a strong word to use.
In any event, if an additive should be used — I’ll be looking for an alternative. I live in Bolivia (that’s in South America, in case your HS geography class has failed you) and the availability of these items is basically non-existent. Our area is a brick-producing zone, so that type of clay is readily available if one owns a shovel.
Does anyone have experience in this area? Is straight Portland with sand going to work fine? “Season” the unit before taking it up to full heat? Additive of some kind?
I’d sure appreciate any and all comments.
Here’s to smoke in yer eyes…
Dan
Replies
I don't think many fireplace folk frequent this site so I'll give you my two bits.
I researched the possibility of building a masonry stoveheater a couple years back and found a 'refractory mortar' was used in high heat areas. A web search should eventually lead you to the precise data needed.
Half of good living is staying out of bad situations.
Forget the primal scream, just Roar!
My mason just finished building a "Masonry heater" fireplace for my house. Temperatures in the fire box can reach 1200 deg. F. All the firebrick was lightly mortared using a refractory mortar as mentioned in an earlier post. I will try to find the manufacturer when I get home. Good Luck.
Tim
Ideally, you should use fire brick and fire clay mortar. Fire brick are usually made from fire clay and they are yellow/biege in color. Fire clay has fewer impurities and oxides than the surface clays and shale that regular brick are made of. This allows fire clay to withstand higher temperatures without softening or cracking. Fire brick and fire clay mortar are also called refractory brick and refractory mortar.
Although fire brick and fire clay mortar are ideal, I've seen many fireplaces made with red brick, especially in older houses. Fire clay mortar (made with one-third fire clay, one-third portland cement and one-third sand) has gone in and out of the code where I live. At this point, it is difficult to find because it is no longer required. Regular masonry mortar is the norm for fore boxes in this area. Inspectors generally require fire brick in the fire box here but the IRC does not require them. (See R1003.5 Fireplace walls). I recommend using fire brick and refractory mortar. If you can't get these materials, however, I would not lose sleep over using regular brick and mortar. They should work fine and I don't think they'll explode.
The explosions happen when you build a hot fire before all the moisture in the mortar has either reacted with the cement or evaporated. You need to give the mortar a few weeks to gain strength and then build small fires to start with, to gradually warm and dry the brick mass.