Firebrick and castable refractory for the BrickWood Box

I have more questions about materials.

I have found that the standard concrete block around here is 8x8x16 (BTW is it the same as cinderblock?). That size will completely mess up the design, which is for 6x8x16. Still looking for the right size. Is 6 the High or width?

FireBrick: It seems easier to find the 9 x 4 x 2 1/4. Is it ok to replace it or do I continue to look? I am just starting to make measurements for the hearth slab.

The instructions says the hearth slab will need 3.5cf of castable refractory, but I do not see where, unless it refers to the cinderblock.

I also want to verify:

The BrickBox Subbase/hearth slab calls for:

  • High Strength concrete mix (12x60lb bags or 9x80lb)
  • It also has 3-cinderblocks with insulation mix inside and possibly a couple small ones

Refractory Slab insulation Panel

  • stainless steel fibers
  • Castable refractory
  • Insulation (Cement and Perlite)

Quantities: Materials state High Temperature Mortar 110 lbs, and page 44 show 100 lbs. I imagine the 110 includes 10%?
Is castable refractory mortar the same as refractory mortar?

I found this product:

but I have no idea.

Okay, I’ll take the ones I know and a few are @BrickWood topics.

Cinderblock is an older form of concrete block. Functionally they’re the same thing, and I’ve taken “cinderblock” out of my personal vocabulary. The standard 8x8x16 will make an 8-inch thick wall, and throw off all the design dimensions. You might want to keep looking.

The firebrick seldom can be found in the nominal dimension shown in the book. You simply recalculate runs based on the brick you actually have.

Do not substitute refractory mortar for the castable refractory called for. There is a discussion on that topic in the instruction book. The 10% allowance is a good guess.

Good luck!

Thank you for your response. The problem with the firebrick is the thickness. It is 1/4 inch less, and I am afraid it will be too thin and will throw the walls off (Page 107, Step G8). The step talks about exact measurements inside the walls and whatnot. The Grill will not be the correct size when put in because the walls are wider. A solution would be to fill it with Additional mortar.

I don’t want to say “yes” to that myself, though it’s definitely the solution for other types of BrickWood ovens. I’ve put out a call to get a response to that specific question.

I also want to observe that, in general, masonry work is a combination of science and art. The mortar, for instance, is at heart a chemistry combination. You can’t substitute other ingredients, or other types of mortar, and expect the oven to perform as designed. But masons work with the materials they can get. As long as your materials meet technical specs (in this case, low- or medium-duty firebrick), you will be applying a little art to meet the dimensions specified in the drawings.

I do appreciate that you are thinking this through, because it will avoid major stumbles later.