Insulating hearth pour & outskirts of oven footprint?

[waynebergman]

Pour for stand and stuctural part of the hearth went well yesterday. No pun intended. I plan to hand mix the insulating part of hearth on the weekend. As you can see from attachment I have an outer ring 4" thick that will contain my insulating pour. I am not sure if I should go the full distance of the 64" diameter cavity or just say a little past the outer footprint of oven and hearth? I plan to line the inner lip of the outside ring with some eighth inch foam in case of any differences in expansion between the expposed aggragate pour and the insulating cement....any body got any thoughts?

This outer ring should be close to the top height of the oven firebrick floor so if I continue the firebrick at the floor level al the way out to the outer ring perimeter it should give me a nice clean look, but not sure if heat will transfer outbound from cooking floor through all the fire brick and burn fingers and things on the outer edges past the stuco and what not on the top of the open hearth area. Hope this all makes sense it is kind of hard to explain what Iam concerned about. Any suggestions very much appreciated.....Wayne Bergman Garden BC Canada

[Ken524]

Originally Posted by waynebergman

Pour for stand and stuctural part of the hearth went well yesterday.

Hi Wayne,

Do you have more pics of the forms and pour? Your stand design is awesome. I'm curious about the exposed aggregate. It seems like that would be very tricky on a formed project. If you take the forms off too soon, the whole thing slumps, too late and you can't hose off the top layer to expose the aggregate, right?

Your oven will be gorgeous on that stand!

Ken

[Unofornaio]

First of all that looks very nice. I wouldn't worry about the insulating slab expanding on contracting enough to effect the base. If you want to put something in there I would just put standard expansion board. Id be hesitant to put any foam or other low melt temp material anywhere near this area.

As far as heat transfer you can bet those bricks on the outer edge will be very warm or possibly hot to the touch. If you want to have them continue to the edges you could at the point after the thickness of the dome insulation and stucco layer create a thermal break by leaving a 1" gap between where this ends and the next brick starts.

What I'm picturing is an Igloo enclosure with room to spare all the way around the oven correct? But why use the fire brick all the way to the edge?

What would look really sweet is brick cantilevered over the base edge 1" all the way around that becomes the oven landing/loading area.

[Carl]

That looks fantastic. How on earth do you do exposed aggregate when pouring into a frame like this? I'm baffled (but then I frequently am ).

Great work - you should be very proud of the progress so far!

[RTflorida]

Very cool, looks like the exposed aggregate finish in my pool. I know how they did my pool, but I'm with Ken and Carl - how is it achieved in formed concrete???

Enquiring minds need to know, THANKS!

RT

[waynebergman]

Rob the concrete fellow in the crew had sprayed the inside of the form with a retardent of some kind. We were very carefull when shovelling concrete into forms we did not let the concrete scrape the outer wall on the way down so as not to disturb the spray retardent. And you are right the timing of when to stop the pour and let things sit was important. Forinstance after the foundation was poured we had to wait for things to set up so we could take apart the intetrnal stakes that were temporatally holding the iner forms to the right height and level. After things set up the stackes were removed and walls were then poured. Lid for hearth support was screwed on and the 3.5" of stuctural pour. Then the 64" by 6" giant styrofoam puck went in to creat the ring. Now the 4" ring was poured on the very top. All very trick and I think you need to be a concrete specialist or something to tackle this. The ring on top and the overall look was mine but my concreate guys made this all happen. I wouldn't have a clue how to do this on my own......hope this answere some of your questions....below is a link to some photos I have on photo bucket....I will try to add weekly to show progress.Wayne Garden Bay BC Canada

waynebergman - Photobucket - Video and Image Hosting

[nissanneill]

Great job Wayne,
keep it up and all of interested onlookers envious. You have me thinking along similar lines for a base for my daughters oven. Using a section of a large diameter concrete drainage pipe stood on end and rendered with exposed agate/pebbles. Very quick and easy, even to cut an access hole in for storage!

Neill

[waynebergman]

thanks for the help UNOFORNAIO. The 1" break is interesting. The height of the top of the cook floor is going to go straight out to meet the top of exposed aggragate ring. This is the plan to give a clean look. Good point on why fire brick all the way though, I am still in the planning stage so not really sure what I will use. Maybee slate after about 4" outbound from the outer edges of oven footprint. If I had a one inch break what would I fill it in with to stop the heat transfer to the other builing brick or slate. I am still not real clear on how all the heat transfers but I plan on not pouring or laying anything on top of the height of the fire brick floor inside the oven. AT least this was my plan to just have a clean edge going up to but not over the top of the outside exposed agragate edge......Sugestions appretiated....thanks wayne

Originally Posted by Unofornaio

First of all that looks very nice. I wouldn't worry about the insulating slab expanding on contracting enough to effect the base. If you want to put something in there I would just put standard expansion board. Id be hesitant to put any foam or other low melt temp material anywhere near this area.

As far as heat transfer you can bet those bricks on the outer edge will be very warm or possibly hot to the touch. If you want to have them continue to the edges you could at the point after the thickness of the dome insulation and stucco layer create a thermal break by leaving a 1" gap between where this ends and the next brick starts.

What I'm picturing is an Igloo enclosure with room to spare all the way around the oven correct? But why use the fire brick all the way to the edge?

What would look really sweet is brick cantilevered over the base edge 1" all the way around that becomes the oven landing/loading area.

[Unofornaio]

Just a real quick comment on the "Howd they do that?" I don't know if they did it or not, probably, but you also have to use a special mix with a much higher rock content. You can also not use the retardant and go back the next day with a pressure washer. Or do like the new fad and wait a week and sand blast it. This actually works for flat work (sidewalks, patios, etc.) because if any of you have exposed agg at your home you know when it gets wet..watch out its slippery.
Wane-I will get back to your questions later I just got home and Ive been laying block all day in 105 weather I'm BEAT.