Vemiculite Pad

[Balty Knowles]

I just poured a 3" pad yesterdayon top of 7" of structural concrete, perfectly level but.. as the pad dried some loose vermiculite kind of floated to the top & now I have some voids on the surface. they're around theedges of the pad & dont matter structurally but I worry about some hot spots when I lay the floor. Should I patch themwith more verniculite concrete, they're about 1/4" deep? Should I skim a veneer of refrax mortar over the top to make it flat again? Or should I just forget about it

[CanuckJim]

Balty,

Personally, I'd skim coat it with refrax. The major reason is to have a really flat, level surface on which to lay your floor. It's the small problems like this one that add up as you go. Take the time to repair it now; it'll save time down the road.

Jim

[james]

One thought would be if you put together a bed of knotched trowel coated sand and fireclay paste thick enough, you could still lay the floor level. That way you would not have to add a layer of set mortar or concrete, but rather use the sand/fireplace to level out the surface.

What do you think? Jim?

James

[CanuckJim]

James,

Sure, that would work, too. I was mainly thinking of ease and speed. If he has Refrax available, it would be a simple matter to mix up a farily sloppy batch and use that. The whole exercise is about making a flat, solid base on which to lay the floor. Other than that, I don't think the materials matter all that much, so long as the mix is refractory.

Jim

[Balty Knowles]

Thanks Guys It'll be a couple of weeks before I get to it. I travel a lot & limited to weekends for the project. I need to get refrax to assemble the oven anyway but I like the sand/fireclay mix. What is the correct mix?

[jahysea]

Hi. I used 1:1 Sand/Fireclay mix per the original plans. I would think it would have leveled your situation out, not certain.

[Balty Knowles]

I just down loaded the Pompei plans, wish I'd done it a week ago. I'm a little worried about my insulated pad, now 1 week old.
First I used a mixer rather than mixing by hand, although I was careful not to over mix, I read that may reduce the themal properties. Secondly it is only 3" thick.

I was thinking of increasing the thickness by laying an Island of split firebrick surrounded by some more vermiculite concrete. (as on p 22) The oven floor is going to be a little high as it is (approx) 46" this would raise it to 48"

I like the idea of some more thermal mass in the floor but what do you guys think? Will the island add a little to the isulating properies of the 3" pad underneath or will it actually do the opposite?

Hate soggy bottoms

[Balty Knowles]

Big weekend for me. I solved my insulation issue by adding another 3 " of vermiculite concrete. I inset a sub floor with split fire brick then skimmed over with a veneer of high temp mortar before laying the floor. I found that the bricks were neither straight, square or dimensionally similar & ended up shaving 1/4 " of the dimension to get the floor to fit with minimal gaps. Over 500 cuts on the saw, which I also discovered is not square either. I'll lay a bed of sand/fireclay under the floor & sand it flat next weekend.

[james]

Hard work but well worth it. It looks great.
James