Dannos Limey Build (Suffolk UK)

[UtahBeehiver]

Re: Dannos Limey Build (Suffolk UK)

Hey Bookem,

Nice work on the vcrete. Very smooth and consistent shape, ummm.....has me thinking about adding a vcrete layer over the my CF insulation.

[Bookemdanno]

Re: Dannos Limey Build (Suffolk UK)

Thanks Russell.

My insulation of choice was very soft, much softer than CF, so i'm glad that i decided to set a Vermicrete layer. It'll provide a good intermediate layer for the final render, or Stucco, as you call it over there. I'm just worried about wayward footballs leaving meteor strikes in the dome.

Just read the last posts from you and Nat too. I'm so happy we have the Gulf Stream effect over here, you're talking about the impending snows and the leaves are still green on the trees over here!

[Laurentius]

Re: Dannos Limey Build (Suffolk UK)

Thanks Russell.

My insulation of choice was very soft, much softer than CF, so i'm glad that i decided to set a Vermicrete layer. It'll provide a good intermediate layer for the final render, or Stucco, as you call it over there. I'm just worried about wayward footballs leaving meteor strikes in the dome.

Just read the last posts from you and Nat too. I'm so happy we have the Gulf Stream effect over here, you're talking about the impending snows and the leaves are still green on the trees over here!

Curious, what was your insulation?

[Bookemdanno]

Re: Dannos Limey Build (Suffolk UK)

I used an initial layer of 20mm Ceramic Blanket which i had from an old kiln, then a layer of high temperature mineral wool which is Rockwool Fire Barrier. A mineral wool based blanket roll to provide a fire stop of 30-60 minutes in roof voids, etc. The temperature rating (up to 600c continuous and 1000c peak once) of the Fire Barrier is much closer to what is expected at the brick face, hence the layer of Ceramic Blanket first. I was told that the Rockwool has better insulation properties than CB, but the downside is its lesser tolerance of heat. CB is much more dense and rigid material also, with the Rockwool more like sheeps wool.
My decisions were also based on the fact that my oven had budget restraints, and the oven dome was not a full firebrick version either. I also wanted to prove that a lower grade of oven could be built, for minimal cost, but still have a high enough performance to give results. Inbetween a Cob Oven and a Firebrick Oven.
If more money were available, i'd not have taken the route i had and if i had a paying customer, they'd be steered towards Firebrick and CB unless they understood the compromises.

[Bookemdanno]

Re: Dannos Limey Build (Suffolk UK)

Final push for the line!
Day off today and a nice weather afternoon, so i got out there and set the first scratch coat of Hydarulic Lime Render...



weather permitting i'll get the final waterproofed coat on tomorrow!

[Laku]

Re: Dannos Limey Build (Suffolk UK)

Shouldn't you wait until the vermicrete is dry? ( I'm assuming you finished it when you posted the pictures)

[Gulf]

Re: Dannos Limey Build (Suffolk UK)

Danno,
There is a lot of water in vcrete. It takes a long time to dry it out. I waited, per headings of the experienced members of the forum, to stucco over the vcrete. I also added a vent at the top, just in case I had not waited long enough. I call mine the standard size vent .


If it were me I would, at the very least drill, a hole in the apex of the dome through the stucco to the fiber insulation layer. This may help keep your shell from cracking while releasing all that steam pressure which is inevitable when you fire it up to cooking temps again. You can always fill the vent in when you are sure that the vcrete is dry.

Just sayin

[Laurentius]

Re: Dannos Limey Build (Suffolk UK)

By no means, drill a hole in your stucco! Yes, its steam, but it's being dispensed over a wide surface area as a gas, its not confined to a small space under tremendous pressure. Don't risk causing additional problems by overreacting.

[Gulf]

Re: Dannos Limey Build (Suffolk UK)

By no means, drill a hole in your stucco! Yes, its steam, but it's being dispensed over a wide surface area as a gas, its not confined to a small space under tremendous pressure. Don't risk causing additional problems by overreacting.

OOPs

But, I still stand by my advice or, at the very least, I suggest being very methodical, slow, and careful when bringing her back up to temp. It's not my experience that I am relaying. It is just the advice that I have read and trust about not trapping lots of water in side the shell.

Again, Just sayin

[david s]

Re: Dannos Limey Build (Suffolk UK)

Yes, I believe you need to dry the vermicrete layer, then do the curing fires, before proceeding to do the stucco. Also you should cover the stucco as soon as it's done to retain the moisture in that layer to make it stronger. I find wrapping the whole dome in clingwrap and leaving it for a week works well.

[deejayoh]

Re: Dannos Limey Build (Suffolk UK)

Drilling a hole as Gulf suggests that goes through the vcrete to the rockwool makes sense to me. Water vapor can pass inward through the insulating blanket (which is quite permeable) and exit through the hole. Drilling through the stucco to the vcrete layer would not make sense as it runs into the issue Laurentius raises - there is no way for vapor to get to the hole.

[Gulf]

Re: Dannos Limey Build (Suffolk UK)

I am referring to post #50 of this thread. Where it appears that the scratch coat has already been applied to what I assume is wet vcrete.

Steam is a funny thing. It will develope at 212 degrees at sea level. It might not develope at 220 degrees at sea level if it is confined to a space which exerts enough pressure to confine it like in a pressure cooker. But, finally given a weak spot to get to freedom it will rapidly expand many times the minute water droplets origional size. The expansion will be violent . I say either dry it up first, give it some where to go, or take it damn slow .

[david s]

Re: Dannos Limey Build (Suffolk UK)

The accompanying experiment details how much water is in vermicrete and how long it can take to dry out. Although the results refer to a 5:1 vermicrete slab, it still contains the same amount of water by proportion. Remember that every litre of water creates 1000 litres of steam. Do not be in a rush.

[Laurentius]

Re: Dannos Limey Build (Suffolk UK)

Hi Gulf,

Think of stucco as you would plaster of paris, as a membrane rather than a barrier. In my younger days, if someone broke an arm or leg, they would have been encased in a plaster of paris cast, which allowed air and moisture pass so you wouldn't rot, but you would itch like hell. So in time the moisture trapped in your dome would dry up. One of the weakness of stucco is, if develops cracks or fissions that allows water to penetrate it will be destroyed, which is way more costly than patience. My advice to someone currently building is to dry your dome before you insulate and if you are insulating with vcrete, dry again. Prevention is the best cure.

[Bookemdanno]

Re: Dannos Limey Build (Suffolk UK)

Vermicrete has been applied for a week, and is only about 2 inches thick.
The moisture is a worry, as i rushed the seasoning of my oven and cracked up.

I think its always going to be a battle over here in UK as each winter the oven is going to soak up a load of moisture, and that'll need driving out. My outer layers are lime based, which is able to pass moisture back and forth much more than cement based layers. I'm going to set a 500w halogen lamp inside to run for most of a week first, and monitor the temps. Then set some small fires after that. Thanks for your concern chaps, wish me luck!