Just a thought

[mikeye15]

OK I know this is not a WFO question. I am also planning a true BBQ pit next to the WFO. Would you use vermiculite morter mix to fill the masonry block cavity of the oven walls or is that overkill.

[nissanneill]

Mikeye15,
Vermiculite is an insulator and your cement blocks are a heat absorber (although cement is not recommended to get too hot as it will break up and self destruct over a short time).
You will be gaining little using vermiculite apart from a little weight. It is also not as strong as Portland concrete.

Neill

[mikeye15]

I get it. I would actually be hurting myself because I would insulate at the first half of the block. It is a low heat pit probably stay at around 250 F. I want it to hold the heat.
Thanks for the input

[Chef]

Mikeye:

We built a BBQ pit next to our WFO for the floor of the pit we used refactory cement. Just as an FYI make a cover for the BBQ so the cement does not get wet, after the sprinkler system wet ours and we used the BBQ the cement would "steam" so we now keep it dry with a wood cover.