Does the vent and chimney area need to be fire brick?

[browny]

Hi folks,

I'm playing around with ideas at the moment and thought I'd seek some input on the chimney construction.

The basic form I am going for is an igloo with vent, stainless flue liner in a brick chimney and a decorative front facade that hopefully evokes an art deco feel.

At the moment my idea has the vent as a minimalist free standing structure out of firebrick, around which I have a decorative 'veneer' of nice face bricks. I was only going to butt these two together so the veneer acts as a buttress to the chimney arches but there is a little potential for the two to expand/contract individually.

The downside is that this starts to make the vent area deeper and it becomes a bit more fiddly to build.

So my question is whether this is overkill and could I simplify things by building the whole vent out of face brick (dry pressed Bowral Blue, Bricks Export - Bowral Bricks from AustralBricks). A bonus is this saves me some fire bricks which are relatively expensive and hard to find. This would give me a more monolithic structure rather than a liner + veneer.

Another idea is to use a few fire bricks only in the direct direct path of the hot gases as they exit and head up the chimney. Ie around the throat area. I'm not sure whether this will cause dramas with different expansion rates etc though?

I'd be interested to hear your ideas.

Thanks, Tim

[Les]

Re: Does the vent and chimney area need to be fire brick?

The gasses escaping the chamber are pretty hot - firebrick is recommended. You mentioned you are using a stainless flue liner so there s/b no issue. I would separate the brick from the flue a bit and slop some vermiculite / portland in between the two. Thats pretty much what I did but my flue was clay.

[cobblerdave]

Re: Does the vent and chimney area need to be fire brick?

G'day
Firebrick may be the recommended but you can certainly use commons like you pointed out in your link. My oven only the dome/hearth is built of firebrick, the entrance chimney and outer cover is just brick. They certainly look a lot better as firebrick are pretty bland ,and expensive sh%ts as well.
The clay flue as Les used is not used in Australia at least Ive not come across it
Regards Dave

[browny]

Re: Does the vent and chimney area need to be fire brick?

The gasses escaping the chamber are pretty hot - firebrick is recommended. You mentioned you are using a stainless flue liner so there s/b no issue. I would separate the brick from the flue a bit and slop some vermiculite / portland in between the two. Thats pretty much what I did but my flue was clay.

My idea is basically to leave an air gap to the bricks but come up with a way to allow the liner to float. So it can do it's own thing with expansion.

My oven only the dome/hearth is built of firebrick, the entrance chimney and outer cover is just brick.

The clay flue as Les used is not used in Australia at least Ive not come across it
Regards Dave

Yeah that was my basic idea but I'm happy to take advice on board if that will set me up for problems later on.

I haven't even bothered to look for clay liner here. Basically if it's not a shelf item at Bunnings then it's too hard.

[browny]

Re: Does the vent and chimney area need to be fire brick?

Eventually I've stumbled across this...

As a rule, any brick not exposed to direct flame do not need to be fire brick.

[Les]

Re: Does the vent and chimney area need to be fire brick?

I would error on the side of caution - the gasses rolling out of there are really, really, hot. It would be a real drag if the brick decided to spall.

It's just my opinion but I respect it

[browny]

Re: Does the vent and chimney area need to be fire brick?

I agree. I value my investment in time and effort too much to go and cut corners.

But by the same token I don't see any point in overbuilding just because I don't really understand what materials I actually need to use.

I am still interested if there could be some sort of a compromise where fire bricks are used sparingly for the hottest areas of the chimney and solid clay bricks for the rest.

[cobblerdave]

Re: Does the vent and chimney area need to be fire brick?

Gday
Use firebrick for the area above your oven mouth, then go commons for the rest.
My own oven has I row only above the oven mouth and the rest are all secound hand brick . It was in the plans and the money I saved on firebrick I spent on ceramic blanket. I'm sure that with firebrick over the $4 mark now that's a saving. My oven been in use for 4 years with no ill results
Regards dave

[GianniFocaccia]

Re: Does the vent and chimney area need to be fire brick?

Use firebrick for the area above your oven mouth, then go commons for the rest

I second this. You may also want to use firebrick for the oven-side of your brick vent.

I suspended my SS flue and sealed it to my firebrick vent with refractory caulk.

[ocafra]

Re: Does the vent and chimney area need to be fire brick?

I saw this post in Forno and wanted to follow up. I am at the point of connecting my SS Anchor plate to the Oven. I built out the opening, but trying to figure out what the final layer to attach the SS Anchor plate "should be." Seems like some attached it directly to the firebrick, but others have mentioned possibly installing a layer of insulation (Vermiculite/Cement, Ceramic Insulation board, etc) between the firebrick and SS Anchor plate....thoughts on a standard way of doing this? Since, the firebrick absorbs heat, was concerned that the firebrick would heat up over time and cause problems with the Anchor Plate if not separated by some kind of insulation.

[UtahBeehiver]

Re: Does the vent and chimney area need to be fire brick?

You will need something of substance to attach the anchor plate to. Fire brick is what you will anchor to. Vcrete or CaSi does not give you the structure to anchor too. What they are talking about in the thread is the whether to insulate the vent stack, especially a single wall vent pipe. I anchored to the fire brick and ran a bead of high temp caulking (2000 F plus rating) under plate for sealing the plate.

[ocafra]

Re: Does the vent and chimney area need to be fire brick?

Thank you for the quick response. When you say firebrick, are you talking the insulating type (light bricks) or internal oven type (heavy bricks)?

[UtahBeehiver]

Re: Does the vent and chimney area need to be fire brick?

IFB no strength, oven type (heavy) yes

[checker1965]

Re: Does the vent and chimney area need to be fire brick?

Hi Utah, can I ask u a question about your comment that u wrote?
"I anchored to the fire brick and ran a bead of high temp caulking (2000 F plus rating) under plate for sealing the plate."

This is what I want to do, what kind of anchors did u use? I am so afraid to crack my bricks. I also am leaning towards using the hi temp caulking, can I or should I use that abundantly to insure a good seal? Any advice??
Thank you sir!
Checker

[ocafra]

Re: Does the vent and chimney area need to be fire brick?

I used simple 1.25" cement screws w/ stainless steel washers, and predrilled the bricks. Worked great. Two generous lines worked for me. I actually went back later to extend chimney up, and when I removed the base I could see it was sealed more than adequate.