sand under firebricks?

[Dagored154]

Re: sand under firebricks?

Thank you so much Chip. I am going to order the FB board tomorrow morning and go with that design. not sure what to do with the soapstone I bought. maybe I will put it on the front face of the oven.....

[mrchipster]

Re: sand under firebricks?

You will go through lots of wood with no insulation under the floor.

Just because your friend builds them this way does not mean it is best practice, please research heat loss through the floor or insulation techniques on this site. I have 2.5 inches of vermicrete and 2 inches of FB board under my floor and can cook all week on one firing of the oven, pizza first night and ribs on day 6. With bread, roasts and casseroles in between.

Chip

[Dagored154]

Re: sand under firebricks?

an old acquaintance of mine has built dozen of home and commercial ovens. and has used them as well. He suggested the soapstone bricks underneath instead of the FB board. He sure seemed to know what he was talking about. I hear what you are saying so I will speak to him when he returns from Canada.

[mrchipster]

Re: sand under firebricks?

Do you mean soapstone or insulating fire brick? Soapstone is a great conductor of heat and not an insulator, FB Board is an insulator and your plan to use soapstone will be a serious mistake. You may not even be able to get your oven up to temp due to the thermal loss.

Insulating firebrick may be a useful choice but I think it would be quite expensive when compared to FB or some other ceramic insulating board.

Just my two cents.

Chip

[Dagored154]

Re: sand under firebricks?

I am using 3 1/2" soapstone bricks under the fire brick instead of the FB Board. can I just use sand underneath them and not mix it with fire clay? any thoughts.

[david s]

Re: sand under firebricks?

There has been plenty of discussion on using broken glass as an insulator if you do a thread search. It was used extensively prior to modern insulating materials. The air spaces created between the bits of broken glass are what gives you the insulation value. Curved glass is better than flat pieces because they create more air spaces.

[big dumb & stupid]

Re: sand under firebricks?

Just to confuse you have you thought of using broken glass under your hearth, loves heat and if broken to very small pieces it will tick all the boxes.
Sri Lanken bakers use this method and they have some very hot/even ovens

[cobblerdave]

Re: sand under firebricks?

Gudday
Just hoping for a few more pics on your progress to date

Regards Dave

[cobblerdave]

Re: sand under firebricks?

Gudday
Thanks for the the pics... ovens looking good!!!....your on the home stretch now...

Regards Dave

[Poetryart]

Re: sand under firebricks?

another view.
i hope.

[Poetryart]

Re: sand under firebricks?

yippee! It did, it did!
The perlite/portland cement has been drying for almost 24 hours. There's still a little "crumbly" surface on top, except where I dumped the slush from the bottom of the wheelbarrow - seriously wet stuff - it's now the firmest. Should I go back and put a layer of soupy portland on top to seal it? I do plan to put some tiles on for finish. This weekend we'll put the FB blanket on, and the layer of portland/perlite on top of that. We still need to decide exactly how to do the flue. We'll stucco for the dome finish.
Don't laugh at the shape of my dome, btw, I know it looks a bit like a big zit...but that will get covered up. I hope....

[Poetryart]

Re: sand under firebricks?

Test - did this photo come through? ~

[cobblerdave]

Re: sand under firebricks?

Gudday
Now...have I got this right? you have used perlite/cement to raise the outer to height?
I only mucked around with perlite/cement but didn't use i in my own oven due to it being built during the biggest "wet" we have had here in QLD so all my insulation was "dry".
The stuff uses and retains heaps of moisture so its going to have to have a considerble period to dry out....all that water you have added is trapped in the tiny holes that gives the stuff its geat insulation value.
I've mixed up a batch and let it cure... it first appears to be softer than cement but will from all accounts support a full blown oven!!! ther'se heaps on the forum!
I'm not sure what your local conditions are in regards to climatic conditions but I pretty sure that the portland cement in that mix doesn't like cold conditions I'm pretty sure that it retards it curing. (We have the opposite it has to be covered and kept wet lest it cracks)
So I'd be patient and see how it sets over time... its to be covered in tiles so this will protect its soft surface!
Hope this helps

Regards Dave
PS No more excuses.....some pics...please
If you had trouble uploading them just ask I'm a computer illiterate so I could probally explain in English

[Poetryart]

Re: sand under firebricks?

Hey Cobblerdave! Yep, back to oven building. I've got a question for you, though. I hope I didn't mess up...I put in 4 inches of insulating concrete this afternoon. I built the oven on the fb boards and fire brick and needed to raise the rest of the platform/ hearth to match the level of the oven floor minus the dimension of the mortar and tile I'll put in for finish out. The concrete stuff doesn't seem to be setting up at all. It's still kinda crumbly feeling. It's also still quite wet. I did it to the consistency of oatmeal, so I don't think I did it too wet. What should I expect of the concrete?
Thanks, glad to hear your hand is healing well. - Poetryart

[cobblerdave]

Re: sand under firebricks?

Gudday Poertyart
How things going? survived the winter? back to oven building yet?
Summer in Brisbane has again been wet.....soaking oven again ! waiting for winter cool and dry.... perfect for wood ovens in QLD Aust.
Hands on the mend....still gets sore....but out of bandages so I feel normal again


Regards Dave