finally started the oven

[ericecon]

I'm planning on a 42" pompei (low dome).

I cut my first bricks today just to make sure the saw actually works since it's borrowed. I have all the bricks (I hope), 2" ceramic fiberboard, 3" of insulating blanket, and dry mortar (brickseal bond is on the metal pails-I think it's from the UK). I'm leaning toward the stainless double wall pipe for the chimney and stucco on the oven to finish it.

Before I actually start assembly I have some questions:

1) should I put plastic under the insulating boards? If so, do they cover the entire hearth or just under the boards?

2) I see some talk about using a wet mix of sand, fireclay, and water to level the bricks on the fiberboard and they say the board soaks up the moisture rapidly. Does the board getting wet affect the structural ability of the board? Does it still insulate if wet?

Thanks in advance

[david s]

Re: finally started the oven

I'm planning on a 42" pompei (low dome).

I cut my first bricks today just to make sure the saw actually works since it's borrowed. I have all the bricks (I hope), 2" ceramic fiberboard, 3" of insulating blanket, and dry mortar (brickseal bond is on the metal pails-I think it's from the UK). I'm leaning toward the stainless double wall pipe for the chimney and stucco on the oven to finish it.

Before I actually start assembly I have some questions:

1) should I put plastic under the insulating boards? If so, do they cover the entire hearth or just under the boards?

2) I see some talk about using a wet mix of sand, fireclay, and water to level the bricks on the fiberboard and they say the board soaks up the moisture rapidly. Does the board getting wet affect the structural ability of the board? Does it still insulate if wet?

Thanks in advance

1. The idea of plastic under the insulating board is to prevent water wicking up from the supporting slab. You could either cover the whole supporting slab or just the area under the floor, but as water would be wicking from the walls of the stand then one would presume that that is where you need the barrier. An alternative to sheet plastic is to create some kind of waterproof barrier or sealer between the top bricks of the stand and the supporting slab, or waterproof the whole of the supporting slab with an additive like xypex. I do the last option.

2.Yes the board will suck the moisture out of any mixture placed on it.No, I don't think it affects the structural integrity of the stuff, but some one recently posted that they were advised against using it because it can dissolve. This led me to conduct an experiment with my calsil board in which I soaked a small piece of it in a cup of water. After 3 days of complete immersion and some twice daily agitation the stuff had not dissolved in the slightest. Calsil board may vary from different manufacturers so can't say for sure if they would all behave this way. One member (Cobblerdave I think) came up with a great solution and that is to smear margarine all over the board to waterproof it before using the clay/sand floor brick levelling mix. You could also use an acrylic sealer to do the same job. Or you can make the mix up dry.

Any wet insulation will have its performance compromised if wet because the water in it will act to transfer the heat.

[boerwarrior]

Re: finally started the oven

I found that I did not need anything under my firebrick floor to 'level' it - the CalSil was close enough to flat. So I recommend trying this first!