On with ny build, a couple more questions?

[vincentvega_uk]

A while ago I asked for some advice regarding my oven build which I had plans to start.
Well, now I have managed to get this thing started and have just poured my suspended slab to form my hearth.
Before I begin building the oven chamber I was hoping to run a couple more questions by the knowledge of the pro's on here!!

I now plan on poring a vermiculite concrete slab, on which I will have calcium sil board then my firebricks.
How long should I leave the vermiculite concrete before starting the brickwork? (will be covered up)

Do I need to install any kind of fire break between the inner entrance arch, which will be formed out of fire brick, and the outer entrance arch?

I have read that when using fire cement, the joint with should be tight, i.e less than 5mm.
When I build the chains of the dome what is best practice to do with the outside of the dome where the joint width will be larger, (I don't plan on cutting each brick with a taper!)?

Many thanks in advance again.
I will get some photos up of the build when done!

Cheers

Allan

[tusr18a]

Re: On with ny build, a couple more questions?

How long should I leave the vermiculite concrete before starting the brickwork? (will be covered up)

The cement should be set and ready for ceramic fiber board and hearth bricks in 48 hours or less.

Do I need to install any kind of fire break between the inner entrance arch, which will be formed out of fire brick, and the outer entrance arch?

No fire break is necessary

When I build the chains of the dome what is best practice to do with the outside of the dome where the joint width will be larger, (I don't plan on cutting each brick with a taper!)?

I did not taper my bricks either. With that said, I spent a lot of money on high temp mortar to fill the voids between the bricks. If you are using a home brew, this is less of an issue. Otherwise, be prepared to spend more money on high temp mortar than you expected. This is one of the reasons my wife called this my $150 a weekend 3 year project.

[david s]

Re: On with ny build, a couple more questions?

Hi Alan,
on allowing the vermicrete slab to dry the attached doc might be useful to you, although using the weather in the UK to dry it may be problematic. You could cast a block of the stuff the same thickness as your slab and then weigh it periodically to test the dryness.
You do not have to create a firebreak to insulate the outer arch, but I believe it is a good idea. Some place it between the dome and the arch entry, some between the arch entry and the outer decorative arch. Apart from reducing conduction and therefore heat loss, it can also act as an expansion joint to allow the inner parts of the oven expand without placing undue stress on the colder outer bits. To do this you do need to make it from something that will take compression though.
Many builders have used the homebrew mix and reported that it performs better than proprietary high temperature mortars. It will do the job well for you. You can jamb some broken brick bits into the larger gaps on the outside to fill them.

[vincentvega_uk]

Re: On with ny build, a couple more questions?

Thanks for the advice guys.
I have looked into the homebrew mix in more depth and as you state, it looks better for the job with having wedge shaped joints, I will go with that!

Still undecided on a fire break though!

Also, any advice on securing the fire blanket around the dome? I was thinking of using chicken wire?

Thanks Again

Allan

[deejayoh]

Re: On with ny build, a couple more questions?

Using HS50 or other high temp mortar probably costs more than buying a cheap saw at HF and selling on Craigslist at the end + using home brew. It's at least close.

I think I paid $60 or something for a single bag of HS50 and guesstimate it would have taken 3-4 to finish the oven (first one lasted maybe 3 courses). I netted out at about $150 for my saw (after resale) and spent maybe $25 for homebrew components.

Rebar tie wire works great to secure the insulation around the dome. Flexible, strong, and cheap.

[david s]

Re: On with ny build, a couple more questions?

If you set a few wire loops into those gaps in the bricks on the outside then it provides something to anchor the chicken wire to.

[vincentvega_uk]

Re: On with ny build, a couple more questions?

Thanks for all the advice.
Hoping to make more progress this weekend!


Cheers

Allan