Thickness of vermiculite concrete

[alexi82]

Hi everyone,

Aside from losing some insulation properties, do you think a 2 inch layer of vermiculite concrete will have enough compressive strength to support the oven etc... Made a minor height calculation error and don't want to go too high. And am trying not to spend 300 bucks on insulating board which is 2 inches thick.

I figure if it's going to hold, then I don't mind losing a bit of insulation. Can also put some sisulation under and maybe even in it to add extra insulation properties?

Thoughts?

[cobblerdave]

Re: Thickness of vermiculite concrete

G'day
It's not its compressive strength that any is problem. 100 mm/4ins of pearlite cement is worth 50mm/2 ins of ceramic board or blanket in its insulation value.
Above all insulated. Find the extra 50 mm/ 2 ins pearlite cement if you can
Regards dave

[deejayoh]

Re: Thickness of vermiculite concrete

2 inches of vermiculite is not near enough insulation. Buy the CF board. With all the work you are going to put into the dome, the cover, etc - You will regret not spending the $300 later when your floor and oven will not stay hot for very long.

[Les]

Re: Thickness of vermiculite concrete

Increase your insulation and raise your floor to correct the error. You do not want to cut this corner. You can skimp on the dome insulation but the hearth is a massive heat sink.

[alexi82]

Re: Thickness of vermiculite concrete

might have to be board then...50mm board will be sufficient insulation then? dont want to go 100mm of vermiculite concrete so i guess board it is...dang!

[david s]

Re: Thickness of vermiculite concrete

Sisalation sitting against a conductive material like concrete renders it pretty much useless. It has to have plenty of air around it to work. embedding a layer in the vermicrete slab would be better, but it will then act as a vapour barrier and make drying the vermicrete really difficult. i'm with the others either more vermicrete and or some calsil board.

[alexi82]

Re: Thickness of vermiculite concrete

Sisalation sitting against a conductive material like concrete renders it pretty much useless. It has to have plenty of air around it to work. embedding a layer in the vermicrete slab would be better, but it will then act as a vapour barrier and make drying the vermicrete really difficult. i'm with the others either more vermicrete and or some calsil board.

thanks for that david...was more of a crazy idea as i have a heap of it lying around. won't bother. will just fork out for the board i reckon.

although, anothe question. Ive had one guy at a refractory tell me that his calcium silicate board would need to be 50mm (2 inches), where as another refractory that makes ceramic fiber board says 25mm (1 inch) will be suffice and is the equivalent of the 50mm in calsil...

thoughts?

[cobblerdave]

Re: Thickness of vermiculite concrete

G'day
The question I ask is not really why you need that level of insulation under the hearth.
It's really Why is is 4 ins of pearlcrete such a problem?
Regards dave

[alexi82]

Re: Thickness of vermiculite concrete

Because i have made an error with the height of the wall already, so adding 4 inches of vermiculite concrete, and then the hearth will make it too high....hence I am hoping to get the same effect with 25mm of board...i know its only 50/75mm difference but its enough to make it visually too high...imho...

so if 25mm ceramic fibre board will do the same as 50mm calsil board then sweet...

[alexi82]

Re: Thickness of vermiculite concrete

just noticed i keep switching from metric to imperial inches to mm...

[Greenman]

Re: Thickness of vermiculite concrete

just noticed i keep switching from metric to imperial inches to mm...

It is a skill you need when the world is using different systems. Some of us who started pre metric have an advantage and measuring tapes in both metric and imperial are very handy. With metric you cannot get four fifths of five eights of ....... anything!

[cobblerdave]

Re: Thickness of vermiculite concrete

G'day
Question "visually to high" is that the finished oven top is too high?
Or you final hearth height to high?
What's the perfect hearth height?
A work bench is perfect about 2ins /50 mm below elbow height.
But this is looking down and working down on a task.
Oven height is different. You want too see the back off your oven.. Without bendding down.
And without having your elbows in line with your shoulders ooh! When handling you oven tools.
Perfect is what you find in-between.
Sorry can't be more perfect
Regards dave

[alexi82]

Re: Thickness of vermiculite concrete

inclusive of benchtops etc, the hearth of the oven will be too high...

[cobblerdave]

Re: Thickness of vermiculite concrete

G'day
Are you sure?
Get yourself a stick of pine mark off the heights and prove it to yourself ( not me Im a short shit anyhow).
Regards
nazi Dave

[alexi82]

Re: Thickness of vermiculite concrete

haha yea im sure...

im 6'4"...and its too high for me...which means it's too high! haha...

i hear what you're saying though. i'll have another look at it with fresh eyes in the morning...