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Old 06-22-2013, 11:02 AM
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Default Drying out vermicrete hearth insulation slab

Hi, im just about ready for the vermicrete hearth insulation. Its sitting on a concrete slab and surrounded on 4 sides by blockwork. I'm wondering about letting it dry out in this climate(Wet!) Do I need to keep it covered, maybe build a flat roof out of ply over it or something? Obviously with normal concrete we just leave it exposed and it dries with time but from reading here I may need to keep this stuff covered and it needs a week of drying before i can sit the oven on it?
I'm also thinking for building the dome insulation that I may need to do the same?

Thanks

R
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Old 06-22-2013, 11:50 AM
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Default Re: Drying out vermicrete hearth insulation slab

Do keep it covered. Even after it is cured this stuff will soak up water like a sponge. You can cover it with a raised tarp to keep the rain out but allow air to circulate. A temporary ply wood lean-to would help. I started out with a tarp, then a tent and a tarp. I ended up building a permanent shed over my build.
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Its sitting on a concrete slab and surrounded on 4 sides by blockwork.
I'm a little intrigued by that statement. I think that you might need to include some weep holes at the base of those blocks to have another escape route for some of this and any future water problems. Now is also the time to think about a moisture barrier between the concrete hearth and the insulation.

Can you post a pic of what you have completed so far?
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Old 06-22-2013, 01:56 PM
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Default Re: Drying out vermicrete hearth insulation slab

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Originally Posted by Gulf View Post
Do keep it covered. Even after it is cured this stuff will soak up water like a sponge. You can cover it with a raised tarp to keep the rain out but allow air to circulate. A temporary ply wood lean-to would help. I started out with a tarp, then a tent and a tarp. I ended up building a permanent shed over my build.

I'm a little intrigued by that statement. I think that you might need to include some weep holes at the base of those blocks to have another escape route for some of this and any future water problems. Now is also the time to think about a moisture barrier between the concrete hearth and the insulation.

Can you post a pic of what you have completed so far?
I will Gulf. Im in the US as the moment but will be home on monday. I'll post a pic then. Hadnt considered weep holes or a moisture barrier.... I could drill vertically down through the slab in a few places I suppose. What would be the prupose of a moisture barrier at this point, wouldnt that just cause my vermicrete layer to retain any moisture? or is it against moisture wicking its way upwards? I did place a moisture barrier in the foundation of the base slab that the walls sit on.

Thanks

Richard
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Old 06-22-2013, 06:49 PM
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Default Re: Drying out vermicrete hearth insulation slab

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Originally Posted by RichC View Post
I will Gulf. Im in the US as the moment but will be home on monday. I'll post a pic then. Hadnt considered weep holes or a moisture barrier.... I could drill vertically down through the slab in a few places I suppose. What would be the prupose of a moisture barrier at this point, wouldnt that just cause my vermicrete layer to retain any moisture? or is it against moisture wicking its way upwards? I did place a moisture barrier in the foundation of the base slab that the walls sit on.

Thanks

Richard
Richard,
You nailed it. When building, we need to attempt to consider two future problems. Water wicking from the stand upward, the possibility of rain being blow in the door, or a failure of the render/cover.
That maybe actually three problems, but rednecks ain't expected to count correctly . The moisture barrier (plastic, paint etc.) is cheep insurance. The weep holes may be added like you suggested. Not knowing exactly what you have started and your finished build will be, I have to give you all of the negatives. The pics will help .
david s and cobblerdave like this.
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Old 06-24-2013, 12:52 PM
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Default Re: Drying out vermicrete hearth insulation slab

Hi Gulf,
Here's what I've done to date. The slab is only 50mm below top of the wall at the moment so I've to raise up the wall a little . I'm thinking of using red brick which will give me a total depth of about 120mm for vermicrete insulation. When the vermicrete is done ill build the oven on it and then after insulating the oven I intend pouring a concrete countertop around the whole thing which will be polished. After the countertop is poured ill put a weather proof render over the oven. I intend for the countertop to slope slightly away from the centre on all sides and to overhang the block work. What to you recommend or think if my plan?
Thanks
Richard
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Last edited by RichC; 06-24-2013 at 12:55 PM.
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Old 06-24-2013, 12:57 PM
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Default Re: Drying out vermicrete hearth insulation slab

In case you can't quite make it out, another photo
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Old 06-24-2013, 01:44 PM
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Default Re: Drying out vermicrete hearth insulation slab

[QUOTE=Gulf;155706]Richard,
You nailed it. When building, we need to attempt to consider two future problems. Water wicking from the stand upward, the possibility of rain being blow in the door, or a failure of the render/cover.
That maybe actually three problems, but rednecks ain't expected to count correctly . The moisture barrier (plastic, paint etc.) is cheep insurance. The weep holes may be added like you suggested. Not knowing exactly what you have started and your finished build will be, I have to give you all of the negatives. The pics will help .[/QUOTE

There is a fourth problem area for water intrusion if you have a flue pipe and that is where the outer shell meets the flue pipe. I guess also the chimney cap is another area. I know mine gets a bit of water in there when stormy weather drives rain horizontal. I also believe that dry porous refractory and thirsty vermicrete will take on moisture from 100% humidity if it's for a fair length of time. It never hurts to fire up your oven in these conditions, just to help dry it a little.
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Old 06-24-2013, 06:21 PM
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Default Re: Drying out vermicrete hearth insulation slab

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Hi Gulf,
Here's what I've done to date. The slab is only 50mm below top of the wall at the moment so I've to raise up the wall a little . I'm thinking of using red brick which will give me a total depth of about 120mm for vermicrete insulation. When the vermicrete is done ill build the oven on it and then after insulating the oven I intend pouring a concrete countertop around the whole thing which will be polished. After the countertop is poured ill put a weather proof render over the oven. I intend for the countertop to slope slightly away from the centre on all sides and to overhang the block work. What to you recommend or think if my plan?
Thanks
Richard
I like the term "weatherproof" . I assume that you are planning an Igloo? I love the Igloo look. An uncovered igloo can raise some problems though. Like the two that I mentioned, the third that I couldn't count ,. The fourth that David brought will be a problem no matter your finished oven style.
If you can keep your oven dry, through out the build, you may not need the weep holes. If not, adding a thin layer of concrete and forming a low spot where you can collect the water, and route it to the outside would help. A moisture barrier on top of this layer would be great! When considering "weather proof renders", you will definitely need to include some type of vent.
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Old 06-25-2013, 05:36 AM
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Default Re: Drying out vermicrete hearth insulation slab

Yes it's an igloo. How does the 'vent' work with this? Does that assume there's an airgap between the insulation and the external render? How is that achieved?

Thanks

Richard
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Old 06-25-2013, 04:05 PM
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Default Re: Drying out vermicrete hearth insulation slab

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Yes it's an igloo. How does the 'vent' work with this? Does that assume there's an airgap between the insulation and the external render? How is that achieved?

Thanks

Richard
The air spaces between the vermiculite grains provide the air space, but you must make the brew lean to achieve this. I use 10:1. Also don't compact it too much.
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