Cob or brick & cement? First time build in Winchester, UK

[bigdavenorcott]

Re: Cob or brick & cement? First time build in Winchester, UK

G'day
Your V-Crete once dry you can dent it with a fingernail , but it will support your oven, no probs. and insulate like a champion..
I have not used vermiculite board , but I've seen it said that it doesn't suite in open situations as it is not completely waterproof.
Just worth a check... If I were you
Regards dave

Ah thanks Dave that's a load off my mind.

I'm in two minds what to do next; I sort of intended to get CaSi board to go under the oven, but my budget is already disappearing over the horizon (I didn't *really* intend to spend anything when I started).

There's 20cm of V-crete on there now (covered up for the minute). What I'm wondering is:

A/ is that insulation enough to just build straight onto?
B/ does this stuff (v-crete) ever get waterproof, or am I going to have to cover the whole bleedin' lot watertight?

At a low oven-related ebb at the moment, seems to be an impossible amount still to do =D

[oblertone]

Re: Cob or brick & cement? First time build in Winchester, UK

Thanks a lot - will do so. Didn't realise you could get vermiculite boards; are they solid enough to build on? If cheaper I'm sold.

I've used them as an insulation layer underneath my oven floor bricks ( storage heater blocks) and it's fairly fragile stuff, almost like a crumbly softwood so I wouldn't use it as a base to build directly upon. My board was 47" x 52.5" x 1" and cost me ?80 if that helps.

[cobblerdave]

Re: Cob or brick & cement? First time build in Winchester, UK

G'day
Your V-Crete once dry you can dent it with a fingernail , but it will support your oven, no probs. and insulate like a champion..
I have not used vermiculite board , but I've seen it said that it doesn't suite in open situations as it is not completely waterproof.
Just worth a check... If I were you
Regards dave

[bigdavenorcott]

Re: Cob or brick & cement? First time build in Winchester, UK

There is an eBay vendor of vermiculite boards based very close to you; he did me a very good deal a couple of weeks ago when I wanted a base layer for my moveable Pompeii. If you're thinking of going down that route then look him up, his trading name is Dorset Stoves and I have no other connection to him other than as a customer.

Thanks a lot - will do so. Didn't realise you could get vermiculite boards; are they solid enough to build on? If cheaper I'm sold.

[oblertone]

Re: Cob or brick & cement? First time build in Winchester, UK

There is an eBay vendor of vermiculite boards based very close to you; he did me a very good deal a couple of weeks ago when I wanted a base layer for my moveable Pompeii. If you're thinking of going down that route then look him up, his trading name is Dorset Stoves and I have no other connection to him other than as a customer.

[UtahBeehiver]

Re: Cob or brick & cement? First time build in Winchester, UK

Some how I missed you thread. Check with Bookemdanno on this forum, he is from the UK and did a build out of solid red and I think heater tiles for the floor as well. He can help you with local advice and material sources. Good luck.

[bigdavenorcott]

Re: Cob or brick & cement? First time build in Winchester, UK

Heh - I knew this stuff was gonna be a pain to work with but it's bloody awful! Hard to believe it'll have the compressive strength to hold the oven, but we'll see...

[bigdavenorcott]

Re: Cob or brick & cement? First time build in Winchester, UK

Are you building an oven or a house? :wink: No, that thing isn't going anywhere... EVER!

Hehehe - part of the driver to finally getting around to it was the need to get rid of some of the huge slab of crappy old concrete outside our back door where the wife wants a patio...

[Archena]

Re: Cob or brick & cement? First time build in Winchester, UK

Are you building an oven or a house? :wink: No, that thing isn't going anywhere... EVER!

[bigdavenorcott]

Re: Cob or brick & cement? First time build in Winchester, UK

For want of any further progress so far (turns out I need to go to work rather than build my wfo), here's a couple of shots of the base in progress.

Bottom filled with closely stacked large concrete demo rubble, then topped off with rammed chalk subsoil.

I was going to pour a concrete slab over this then a layer of vermicrete, but I think instead I'm going to add a layer of precast concrete slabs I've got lying around then pour a thicker layer of vermicrete straight on top of that. Think the concrete slab is overkill - that base ain't going anywhere I don't think; happy to be corrected though!

[Archena]

Re: Cob or brick & cement? First time build in Winchester, UK

Don't mind me - just lurking...

[bigdavenorcott]

Re: Cob or brick & cement? First time build in Winchester, UK

I'm reading a lot of people have used straight vermicrete as an insulation later under the hearth. Do you guys have a view on whether that's enough? I could easily do 4-5" of that and put the firebricks straight on top.

EDIT: Nah I need something else don't I.... Now thinking lay 4" vermicrete over my normal conc slab, then for the sub-firebrick area a sheet of calcium silicate board. That should do it

[wotavidone]

Re: Cob or brick & cement? First time build in Winchester, UK

I've come to the same conclusion about the vermiculite! Am now planning to pour 3-4" of vermicrete over my slab layer, then (if I can find some affordably) 2" of that solid insulation sheet stuff underneath the cooking floor itself. Still trying to get quotes from a few places.

I'd be surprised if your aerated blocks aren't essentially the same thing. After a bit of googling, they're both aerated autoclaved concrete - think their U-values are pretty identical. Are they cheaper than pouring thermacrete?

Cheers

Dave

Probably more expensive but I think, if they don't degrade, that they are an excellent insulator. I helped my mate build an oven in January, and he bought a pallet of 24'x 8" x 6" blocks, for about 2 dollars each. His oven sits on a layer of them, and the enclosure is made from them as well. Certainly holds heat well.

[bigdavenorcott]

Re: Cob or brick & cement? First time build in Winchester, UK

It is worth getting dense firebricks for the oven floor. Some solid red bricks can't take it and will spall, there's probably no way for you to find out if they are suitable. They will probably be ok for the dome though.

Thanks - I'm keeping my eye out for some reasonably priced ones. Storage heater bricks look like they'll work well and are sometimes really cheap

[david s]

Re: Cob or brick & cement? First time build in Winchester, UK

It is worth getting dense firebricks for the oven floor. Some solid red bricks can't take it and will spall, there's probably no way for you to find out if they are suitable. They will probably be ok for the dome though.