#1  
Old 07-27-2008, 05:03 PM
Serf
 
Join Date: Jun 2008
Location: Toronto, Canada
Posts: 4
Default concrete blocks on top of vermiculite/concrete hearth

Hi all,

a quick question about the size and strength of the insulating hearth. I have poured the 4 inch vermiculite/concrete mix on top of 4 inch structural slab for hearth and the hearth extends to the outside of the concrete block stand.

My question is related to constructing the oven enclosure: can i build the walls of the enclosure (which will serve as the support of my roof and all the stone material i plan to clad the oven with) with 4 inch concrete blocks or will this be too much weight for the "cork-like" hearth material to bear? ie. will it compress under the weight and cause structural issues for the oven enclosure, roof, and cladding construction?

Thanks in advance,

CR
Reply With Quote
  #2  
Old 07-27-2008, 08:56 PM
dmun's Avatar
Moderator
 
Join Date: Jul 2005
Location: New Jersey USA
Posts: 4,216
Default Re: concrete blocks on top of vermiculite/concrete hearth

Yes you can build your 4 inch block structure on top of your vermiculite concrete pad. It has tremendous compressive strength. You will want to consider some kind of exterior coating to keep it dry. It's not something you want exposed to the weather.
__________________
My geodesic oven project:
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
,
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #3  
Old 07-28-2008, 12:33 AM
Apprentice
 
Join Date: Jul 2008
Location: Norway
Posts: 120
Default Re: concrete blocks on top of vermiculite/concrete hearth

Quote:
Originally Posted by dmun View Post
Yes you can build your 4 inch block structure on top of your vermiculite concrete pad. It has tremendous compressive strength. You will want to consider some kind of exterior coating to keep it dry. It's not something you want exposed to the weather.
I have no experience with Vermiculite, but I have just installed a 2" layer of cement/perlite as a top-layer under my oven-to-be (underway). This is not something I would recommend to build upon. Certainly the oven itself is heavy, but it fortunately distributes its weight over a fairly large area. To me the cement/perlite layer looks (and feels) suspicious and I would not have installed it if I knew the properties of it.
But Vermiculite may be different (better). I did not have access to it and the perlite was mentioned in the FB instruction as an alternative.

regards from karl
Reply With Quote
  #4  
Old 07-28-2008, 05:04 AM
dmun's Avatar
Moderator
 
Join Date: Jul 2005
Location: New Jersey USA
Posts: 4,216
Default Re: concrete blocks on top of vermiculite/concrete hearth

No, vermiculite and perlite behave almost exactly the same. It looks weird, and you can easily stick a pointed object into it, but it does have high compressive strength.

Is it the best thing to build on? Maybe not, but you can certainly build on it.
__________________
My geodesic oven project:
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
,
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #5  
Old 07-28-2008, 05:06 AM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,855
Default Re: concrete blocks on top of vermiculite/concrete hearth

Could you trim off 4" of the insulation and then build off the concrete supporting slab ? The insulating vermicrete/perlcrete is easy to chip away or cut neatly with an angle grinder.
Reply With Quote
  #6  
Old 07-28-2008, 06:27 AM
Serf
 
Join Date: Jun 2008
Location: Toronto, Canada
Posts: 4
Default Re: concrete blocks on top of vermiculite/concrete hearth

Thanks for the replies.

I was actually considering cutting a section of it out in order to build the blocks on top. The blocks don't concern me as much as the hip roof design constructed of granite stones that i am planning to build on top of it.

i read in another thread that the vermicrete layer has very high compressive strength (as dmum states) and was satisfied by that. Any ideas on what type of mortar I should use to bond the blocks to the vermicrete - refractory or regular? Thanks.
Reply With Quote
  #7  
Old 07-28-2008, 08:08 AM
egalecki's Avatar
Il Pizzaiolo
 
Join Date: Mar 2008
Location: Virginia
Posts: 1,049
Default Re: concrete blocks on top of vermiculite/concrete hearth

I'd use regular. If it doesn't need to heat up, (and I'd say you wouldn't want it to) don't use refractory.

Are you planning to have perlite or vermiculite between your insulating blanket layer and the block enclosure? That would ensure no heat transfer to the outside of your enclosure.
__________________
Elizabeth


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #8  
Old 07-29-2008, 08:00 AM
Serf
 
Join Date: Jun 2008
Location: Toronto, Canada
Posts: 4
Default Re: concrete blocks on top of vermiculite/concrete hearth

Would a 4-5 inch layer of vermicrete be sufficient or should i definitely use the ceramic blanket and if so, does anyone know where to buy some in the Toronto area - shipping from FB was very expensive.
Reply With Quote
  #9  
Old 07-29-2008, 10:08 AM
egalecki's Avatar
Il Pizzaiolo
 
Join Date: Mar 2008
Location: Virginia
Posts: 1,049
Default Re: concrete blocks on top of vermiculite/concrete hearth

I'm using both. It's overkill, but I want to keep as much heat in as possible. I googled "ceramic blanket" and checked ebay for the same, and found out that for me, at least, it was either pay shipping or pay more for the blanket. I ended up spending it on shipping (yes, I think it was a little bit more than it might otherwise have been) to support James and the Forno Bravo community he's set up.

So, I'm going to have 2 layers of blanket and a couple of inches of vermicrete. The vermicrete will basically serve to give me a surface to do finish work. If you aren't going with an igloo, you can get by with just blanket, and maybe some loose perlite or vermiculite around that for safety's sake on the heat transfer to the outside of your enclosure.

I don't know for sure how many inches of vermicrete you'd need without blanket, but I think the plans call for 6 inches if you don't use blanket.
__________________
Elizabeth


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #10  
Old 07-31-2008, 05:35 AM
Apprentice
 
Join Date: Jul 2005
Location: Toronto
Posts: 106
Default Re: concrete blocks on top of vermiculite/concrete hearth

Project1, call Elvis at Alphatherm in Concord, Ontario. He sells a blanket.

Regards, Tony.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Insulation below or above concrete base for Oven Hearth tdibratt Pompeii Oven Construction 5 07-07-2008 05:03 AM
Thermalite aerocrete blocks for hearth insulation? Carl Getting Started 8 04-25-2008 04:51 PM
Poured hearth, questions about concrete and insulation... Frances Getting Started 9 09-14-2007 09:59 PM
Hearth Questions El Puaco Introductions 12 11-25-2006 12:55 PM
Spanning the wood storage below the Hearth slab. Marcel Getting Started 0 08-22-2005 10:13 PM


All times are GMT -7. The time now is 03:48 AM.

Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
2006/10 Forno Bravo, LLC