Plaster on uninsulated outdoor pizza oven

[David Gunnarsson 82]

I have built a pizza oven with firebrick and used Finja fireproof mortar in between.
There is no insulation on it, so it is "raw."
I have test-fired and made pizza in it and it works excellently, but I would like to put a nice render on it and make it weather-resistant for the winter. Should I just use fireproof mortar as render and then concrete paint on it, or are there other better options?
If I use regular render, I assume it will crack when I fire it?

 

[sturnus]

Det bästa verkar vara clay with an admixture of sand and linseed oil.

 

[David Gunnarsson 82]

The best seems to be clay with an admixture of sand and linseed oil.

Would that be a particular clay or sand? Will that hold both heat from the fire and the cold and not freeze in the winter?

 

[InsidersUnited]

Is already nice as it is with exposed brick, instead plaster your lecablock it stands on, and make a nice shelf in oak.

 

[David Gunnarsson 82]

It's already nice as it is with exposed brick, just plaster the lecablocks it's standing on instead, and make a nice shelf in oak.

What I'm afraid of is if the firebrick won't withstand the winter. It absorbs water like sponges and if it then freezes I assume it could crack.

 

[InsidersUnited]

Can't you brush it with water glass? Then the surface and joints get protection.

 

[Dan_Johansson]

What I'm afraid of is if the firebrick doesn't hold up during the winter. It soaks up water like a sponge and if it then freezes, I assume it can crack.

You definitely need to protect it from rain, both to reduce the risk of frost damage, and to avoid having to slowly fire it for a few days to drive out the moisture before each season (or each time you use it)...

The simplest thing to do is just throw a tarpaulin over it...

Edit; it's worth thinking about that you also need to protect the opening, if it rains in there, it doesn't matter how the rest of the coverage looks...

 

[David Gunnarsson 82]

You definitely need to protect it from rain, both to reduce the risk of frost damage and to avoid having to burn slowly for a few days to drive out the moisture before each season (or each time you use it)...

The easiest thing is just to throw a tarp over it...

Edit; it's worth considering that you need to protect the opening too, if it rains in there, it doesn't matter how the rest is covered...

I will probably combine the tarp at the end of the season, but it's not something I want to take on and off every time if possible.

 

[Dan_Johansson]

If you want it watertight, you must have a valve that can release overpressure.

Personally, I would go for insulation, then a layer of plaster, and then a protective roof on top.

But at the same time, since the opening is as high as the roof of the oven (that's what it looks like to me?), you will use up a lot of wood to keep the temperature up, even with insulation...

Edit: leca can't handle "pizza temperatures" in the long run, so make sure it's reasonably easy to take down and rebuild the oven when that happens...

 

[David Gunnarsson 82]

If you want it watertight, you need a vent that can release overpressure..

Personally, I would go for insulation and then a layer of plaster, and then a protective roof over it..

But at the same time, since the opening is as high as the oven roof (that's how it seems to me?), you will use up a lot of wood to keep the temperature up, even with insulation...

Edit: leca can't handle "pizza temperatures" in the long run, so make sure it's reasonably easy to take down and reconstruct the oven when that happens...

If you want it watertight, you need a vent that can release overpressure..

Personally, I would go for insulation and then a layer of plaster, and then a protective roof over it..

But at the same time, since the opening is as high as the oven roof (that's how it seems to me?), you will use up a lot of wood to keep the temperature up, even with insulation...

Edit: leca can't handle "pizza temperatures" in the long run, so make sure it's reasonably easy to take down and reconstruct the oven when that happens...

Yes, as it is now at least, the opening is as large as the rest of the oven, it's like straight back. The idea is a door that can be opened at the bottom for air intake so the heat stays in better.
It works well to make pizza in it already now but it could of course be more energy efficient and use less wood.
The difficult thing with insulation is that it adds a lot to the thickness and then it has nothing to rest on. If I had thought about it from the beginning, it would have been just a matter of moving the building blocks outwards a few cm on each side. If I were to do it now, I would have to build on the width in some way.

 

[Dan_Johansson]

Feel free to post more pictures, it's fun to see how others have done it!

I have built my oven into a small "house" so I first have 50-100 mm ceramic fiber, and then 200 mm "regular" mineral wool ...

If you want to add on, you can always cast a shelf in concrete, it can probably be attached to the LECA edge .. But otherwise, it's certainly possible to "hang" the insulation over, 25-50 mm ceramic fiber makes a big difference, and then you can plaster on it ..

 

[David Gunnarsson 82]

Feel free to upload more pictures, it's fun to see how others have done it!

I have built my oven into a small "house" so I first have 50-100 mm ceramic fiber, and then 200 mm "regular" stone wool ...

If you want to expand, you can always cast a shelf in concrete, it can surely be attached to the LECA edge ..
But otherwise, you can probably "hang" the insulation over, 25-50 mm ceramic fiber makes a big difference, and then you can plaster on it ..

Some miscellaneous unordered pictures, also from the construction.

 

[David Gunnarsson 82]

If you want it watertight you need a valve that can release pressure..

Personally, I would opt for insulation and then a layer of plaster, and then a protective roof over it..

But at the same time, since the opening is as high as the oven's roof (I think it looks like?) you will use a lot of wood to keep the temperature up, even with insulation...

Edit: leca doesn't handle "pizza temperatures" in the long run, so make sure that it is relatively easy to take down and reset the oven when that happens...

I guess I'll have to hope that the leca blocks withstand the heat, simply because the stones at the bottom are cemented against them. When I've used it so far, the underside of the blocks hasn't even become lukewarm...

 

[David Gunnarsson 82]

I guess I'll have to hope that the lecablock can withstand the heat simply because the stones at the bottom are cemented to them. When I've used it so far, it hasn't even gotten lukewarm on the underside of the blocks...

I ended up adding 2.5cm insulation and then plaster.

 

[Jesper Kvarnefält]

What material did you use for insulation? I need to insulate my oven myself.