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    I have questions regarding insulating board under the oven floor? I have heard that it tends to disintarate slightly if it gets wet. I plan on trying to keep it as dry as possible & I was thinking of wrapping it in aluminum foil. Any thoughts? Good idea or bad? Also, is fireclay the mortar that I should use? Thanks.

  • #2
    Re: Questions

    I can't answer your first question but I think fireclay is not really a mortar. Its kind of like a fire brick in powder form if I understand it right....wayne
    see below for my oven album of progress to date


    • #3
      Re: Questions

      Despite my best efforts, my InsBlock has gotten pretty wet. It didn't get rained on, thank goodness, but mortaring is a wet business, involving buckets of water and hoses with a mist nozzle, or a Windex bottle, rags, sponges, etc.

      I have spilled buckets onto my hearth which surely seeped under the board for lasting effect. I have also constantly wetted things down from the top, most severely not from mortaring but from rag-cleaning mortar the next day to clean out the grout lines and make everything look nice and sharp on the surfaces that will be visible. Bottom line, the whole oven is going to get wet over and over before you ever fire it up for the first time. Different kinds of insulation vary in their tolerance to water, but from what I've read of other people's experiences, and from what I can report of my own, InsBlock will take a heck of a lot of aquatic abuse and bounce back dry and strong later on. With a two-thirds built oven pressing several hundred pounds down onto my insulation, I can confidently say that my three-layer InsBlock hasn't sunk a millimeter.

      What kind of insulating board are you using?

      WFO Webpage:


      • #4
        Re: Questions

        I used the FB Board, and it got moist on occasion from keeping the mortar moist. I've noticed no degradation of the board.

        Member WFOAMBA Wood Fired Oven Amatueur Masons Builders America

        My thread: