FB Brand Insulation

[james]

Re: FB Brand Insulation

I think dry and mortarless is fine when you are setting discrete bricks. Try 50/50. That should be good!
James

[blacknoir]

Re: FB Brand Insulation

James, would you recommend a sand/fireclay mix or a refractory mortar layer between the FB board and the firebrick? If sand/fireclay, what ratio would you recommend?

I just ordered my boards today from FB btw.. can't wait to get started laying brick!

-Shay

[splatgirl]

Re: FB Brand Insulation

Thanks so much for the replies.
Mfiore, I think using a DRY mixture of sand/fireclay is the ticket...just like laying patio pavers. Duh. I wish I had thought of/tried that before I wet down a whole bucketfull and tried to trowel it on.
Anyway, I ended up doing as I proposed above which worked pretty good. As you pointed out, James, the particle size of vermiculite is fairly large, and actually, I used perlite which was worse, but it worked great with a little dry sand/fireclay mixture dressing. Success on attempt #1 today! Cooking floor is in and my soldier course is set and ready to be mortared.

I put a tape measure on the boards I'm using before I started the do over just to make sure I wasn't being overly fussy. There was 1/2"+ variation in thickness from one piece to another measured at the exposed edges, plus I'd say I had another +1/4" high spot on one board and close to -1/4 low on another.

Again, I appreciate the comments and advice.

cheers
s.g.

[james]

Re: FB Brand Insulation

Hi guys,

I'm not quite sure what to say. FB Board is very typical (standard) for this type of insulating board, and we haven't heard of any problems with it -- until today. :-). A majority of the FB precast ovens are installed on FB Board, and we use a very large amount of it building the Primavera ovens -- where we mortar down the firebrick floor tiles with refractory mortar.

In terms of making it smooth enough for the cooking floor, vermiculite is very bumpy and the grains are much larger than the sand or sand/fireclay mixture that most builders use to get their cooking floor level. Vermiculite concrete is also very bumpy in texture -- much worse than FB Board. I guess I have always throught that the sand, sand/fireclay or refractory mortar layer between the cooking floor the FB Board provided the ability to smooth out any bumps or imperfections.

We will definitely talk with our producer and ask that they take better care with the finish surface and consistency on FB Board. They have made changes we have asked for in the past (including making FB Board more dense and rigid after seeing the first trial pieces).

I will let you know what they say.
James

[mfiore]

Re: FB Brand Insulation

Splatgirl,

I have no experience with vermiculite, so can't offer you advice.

Unfortunately, the FB board I purchased was also quite irregular. In spite claims otherwise, It was "warped", chipped, and had significant variance in thickness from one board to the other. I was able to use a mix of dry fireclay/sand to level out the bricks on top.

I've been really happy with the forum, and every other purchase from FB, but share your concern about lack of consistency with this product. Perhaps James will chime in.

[splatgirl]

Re: FB Brand Insulation

Hello. First post!
My hearth stand is complete and I'm working on getting my cooking floor set, but yikes is it turning out to be a pain in my butt!
I'm using the FB insulation board (on a hearth slab that I took great pains to get perfectly flat and level), but this stuff is so inconsistent in thickness that there is no possible way that just notch trowling on sand/brick mud would ever come close to allowing me to get those bricks laid nice and flat. There is a variation in thickness of close to an inch between the warped/high/thick spots on one piece of board and the low spots on the thinner sections of board.
So: A. I guess I'm annoyed since I forked over the $$ and chose this route vs. vermicrete because I thought it would be faster and easier.
and B. I get the impression other people haven't had this problem, and that my experience with this is quite a bit different than the experience of other folks who have used this product....? "Dead flat" is SO not what mine looks like.
Anyway, I've just given up on attempt #2 at laying the cooking floor using just sand/mud as a leveling material on top of the board. ARGH. Now I'm looking at sourcing some vermiculite so I can add an inch or so layer of vermicrete on top of the FB board to level it out. Does this sound like a reasonable plan? I'm certainly open to other suggestions at this point since I'm going to have to start over laying the floor again anyway.
Did I mention, argh?

[dmun]

Re: FB Brand Insulation

should i cut the the FB and fire brich so it fits on the inside of my walls?

No. Your oven should be entirely surrounded by the insulation: it's more than strong enough to withstand the weight of your oven. As to whether to cut your floor to fit inside your walls, or build your walls on top of your floor, this is builders choice.

[antonio cefalo]

Re: FB Brand Insulation

howe about problems with the FB sagging over time, also my plan was to put the fb down, place my firebrick on top of that and then begin the walls of the oven on top of that, so it is all on top of the FB. is this the correct approach? or should i cut the the FB and fire brich so it fits on the inside of my walls?
thx

[dmun]

Re: FB Brand Insulation

The blanket is thick and dense, and pretty much stays where you put it. What you do afterword depends on the kind of enclosure you're planning. I wrapped mine after the enclosure walls were higher than the dome, and then just dumped a bunch of perlite concrete around it. Obviously dome style enclosures need more attention to shape than that.

My firebricks were uniform in thickness, so when i laid them out on the insulation board the floor was dead flat. The fireclay/sand layer is just for leveling, no other purpose. When i was standing inside the oven to build the dome the bricks would shift and creak slightly, and I thought it was a problem at the time, but it's never been a problem with cooking.

[antonio cefalo]

Re: FB Brand Insulation

thanks Dmun, for the blanket would i just wrap the oven dry? or do a thin layer of the refrax and have it adhere to that? thanks.

also how would you lay the firebricks onto the fb board? just dry, how do you get a smooth even surface? thanks

[dmun]

Re: FB Brand Insulation

what are your thoughts of using a insulating refractory concrete for the base to insulate and then cover the dome with it?

The castable refractory insulation is expensive and hard to work with. Under the dome you're much better off with the insulation boards, which give you a flat surface for laying your floor. If you're spending the money anyway, you might as well have the best.

Above the dome, it can work. I know that canukjim used one such product in one of his installations. You have to decide: If you're spending the money for professional insulation, why not get the blanket, which is easy to use?

[james]

Re: FB Brand Insulation

If you are looking to save cost, Perlite and vermiculite also work well and are a little less expensive.

If you are looking for professional level insulation and oven performance, the FB ceramic insulation is what they use in commercial ovens -- and it works great.

I have always thought that was the best trade-off.
James

[antonio cefalo]

Re: FB Brand Insulation

Thanks James. what are your thoughts of using a insulating refractory concrete for the base to insulate and then cover the dome with it?

[james]

Re: FB Brand Insulation

Ciao Antonio,

FB Board is definitely rigid enough to handle the weight of the Pompeii or FB precast oven -- a really large number have been installed that way. You can either set your bricks on sand, or on a bed of sand and fireclay (mix it with water and set it with a notched trowel). You tap your bricks to level with a rubber mallet either way.

2" will do it, though you can add a second layer if you would like.

Here is the FB Board pdf brochure.

Good luck!
James

[antonio cefalo]

Re: FB Brand Insulation

Hello James,
Love the Fire board as a floor insulation in lieu of vermiculite. would it be ok to use 4" of the Fire board? my concern is that the stats indicate a 10% shrinkage, so that means a 2" board would shrink by 1/4". is this ok with the heavy oven on it? also, should sand or anything be put on the fireboard before you set the firebricks? thanks!