Joints between Firebricks (a.k.a. There Is No Step 45)

What do we use to fill the gaps between firebricks? Or leave them be? Instructions for Grand Barille at step 7 says that step 45 will deal with this question but I don’t see any step 45. Someone suggested to use Silica sand to sweep into the gaps?

Welcome to the BrickWood forum!

You’ve run into an old glitch in the instructions—it’s not a trick, just a change that never got corrected at step 7. In short, there is no Step 45.

An early version of the Martone Braille instructions called for filling in the hearth firebrick joints. There was an organic food-safe material (actual food, and I won’t mention what it was) that was recommended.

@BrickWood changed the guidance on this because they found that in some cases the material itself was scorching and burning up, doing some not-nice things to the food you were actually baking on the hearth. The ashes from the burned wood are sufficient to fill in those gaps all on their own, and they are free.

The current advice is to leave the hearth gaps alone, as they will fill themselves.

DO NOT USE SILICA SAND OR ANY OTHER INORGANIC MATERIAL TO FILL THOSE GAPS! You will end up eating whatever you put in there. The wood ash won’t hurt your body; but many construction materials will.

Hope this helps clear things up, and I know that @BrickWood has this item on his list for a future revision.

Another quick question. Material list says to use chicken wire but instructions refer to lathe over the insulation. Chicken wire is thinner wire and wider gaps but the lathe is stiffer and has smaller gaps. Is it ok to use either or one is better then the other for stucco to adhere to?

Chicken wire can be understood as a form of lathe. In this case you’re looking for a flexible wire matrix that will conform to the barrel and become embedded in the first layer of stucco. The reasons BWO specifies chicken wire are:

  • It bends and is easily joined between sections.
  • It can be clipped at the ends with an ordinary pair of cutting pliers with virtually no effort (important when a “sproink” sticks out from under the finished stucco shell)
  • It’s dirt-cheap and widely available at home centers.

In general, I’ve learned to take @BrickWood seriously when he says that the BrickWood ovens are designed for “Johnny and Janie Homeowner” to build even if they have no prior background or knowledge about masonry technique. He goes out of his way to spec materials that an ordinary mortal (as opposed to a contractor) can find within 25 miles of their home.

Your questions are very welcome, of course, and let’s keep talking.

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