Under floor insulation

[Luke.Brod]

Hi Guys.

I have bought my oven along with some insulation. The underfloor insulation is Perlite and a cement fondu. It is a 100l bag of P15 Perlite.

My oven internal measurement is 850mm so the floor will be 1 meter diameter with a landing.

My questions are.

1) Is this enough insulation?
2)How thick will it be?
3)should I buy more and do a layer underneath what they have supplied?

Thanks in advance.

[david s]

I find a 100 litre bag is always less than 100 L and the mix will reduce in volume when mixed with cement and water. 100L is 1m x 1m x 10 cm (4") so you should have just enough. The insulating capacity is drastically reduced if too much ce,emt is used. If too little is used the slab is not strong enough. Most builders use a 5:1 mix for perlcrete.
Vermicrete insulating slab PDF.pdf

[Rosy]

Hi Guys.

I have bought my oven along with some insulation. The underfloor insulation is Perlite and a cement fondu. It is a 100l bag of P15 Perlite.

My oven internal measurement is 850mm so the floor will be 1 meter diameter with a landing.

My questions are.

1) Is this enough insulation?
2)How thick will it be?
3)should I buy more and do a layer underneath what they have supplied?

Thanks in advance.

I used Vermiculite in my insulating layer. 5:1 ration of vermiculite to portland cement. You could also use ceramic fiberboard but it is really pricey. The rule of thumb is the thickness of the insulating layer with vermiculite/perilite should be twice what the thickness of ceramic board it. I used a 3" layer of vermiculite and portland cement for my insulating layer. It cannot be too thick as the insulation will help hold the heat.

[Pizzarotic]

It cannot be too thick as the insulation will help hold the heat.

Insulation is used to prevent heat transfer, if it is for holding heat then it is considered thermal mass not Insulation.

[Pizzarotic]

Hi Guys.

My questions are.

1) Is this enough insulation?
2)How thick will it be?
3)should I buy more and do a layer underneath what they have supplied?

Thanks in advance.

1. Probably not, the actual floor insulation should extend at least 50mm past the oven internal walls so you will need 100 litres minimum for the dome plus an allowance for the entry.
2. Minimum 100mm of 5:1 mix 3. Yes, you can pour in 2 batches if you want which will make it easier to gauge how much you will need to mix for the second batch.