My first WFO design, any comments before I build?

[david s]

The insulating slab between the reinforced concrete supporting slab and the cooking floor bricks should be 4" thick if using a 5:1 perlite/cement mix, if it is to achieve adequate insulation value.

A timber stand is a poor choice if the oven is to be out in the weather. A masonry stand is permanent.

Commercial renders contain a waterproofing ingredient which makes them partially waterproof. This allows them to breathe while repelling most moisture. A mix you make yourself does not have this quality. although you can add a waterproof layer over it if you wish.Fully waterproofing the oven will keep moisture in as well as keeping it out.

[Mark1986]

The insulating slab between the reinforced concrete supporting slab and the cooking floor bricks should be 4" thick if using a 5:1 perlite/cement mix, if it is to achieve adequate insulation value.

Hi David,

Thanks I changed the thickness of the perlite concrete design and the wood accordingly.

A timber stand is a poor choice if the oven is to be out in the weather. A masonry stand is permanent.

My inlaws won't allow me to make a permanent foundation like that in the garden sadly..

I understand that masonry would be better, but why is wood that bad? It can easily last 10 to 15 years as I've read, and even more if you treat it. Are there others factors why wood is a bad choice?

Commercial renders contain a waterproofing ingredient which makes them partially waterproof. This allows them to breathe while repelling most moisture. A mix you make yourself does not have this quality. although you can add a waterproof layer over it if you wish.Fully waterproofing the oven will keep moisture in as well as keeping it out.

Thanks I will look for a commercial option!

[david s]

The oven should be there for generations as there's nothing to rust away. A timber stand will deteriorate and move in the weather setting up stresses that might cause cracks in the oven and ultimate collapse from the weight it supports. If it's your only option then I guess it will have to do.

[MarkJerling]

Hi David,

Thanks I changed the thickness of the perlite concrete design and the wood accordingly.



My inlaws won't allow me to make a permanent foundation like that in the garden sadly..

I understand that masonry would be better, but why is wood that bad? It can easily last 10 to 15 years as I've read, and even more if you treat it. Are there others factors why wood is a bad choice?



Thanks I will look for a commercial option!

It will, in large, come down to what type of wood you use and how you look after that wood. As example, I have an old jarrah (Eucalyptus marginata) telegraph pole in our garden. It will probably still be there 100 years from now.
Needs no maintenance and does not seem to rot.

But then, I have a macracarpa (Hesperocyparis macrocarpa) (also called a Monterey cypress) sign at our front gate. It is soft wood and will soon rot away if left untreated. But, even though I made that sign 18 years ago, it's still perfectly fine and all I do to it is give it a liberal coating of a 50/50 mix of mineral turpentine and boiled linseed oil, once very two years or so. It's almost black in colour now, but strucurally, it's perfectly good.

So, wood can work, provided you look after it or if it's the right type of wood.

[Mark1986]

The oven should be there for generations as there's nothing to rust away. A timber stand will deteriorate and move in the weather setting up stresses that might cause cracks in the oven and ultimate collapse from the weight it supports. If it's your only option then I guess it will have to do.

ok, that sounds reasonable! It will have to do for now, because of the choices I've made!

[Mark1986]

It will, in large, come down to what type of wood you use and how you look after that wood. As example, I have an old jarrah (Eucalyptus marginata) telegraph pole in our garden. It will probably still be there 100 years from now.
Needs no maintenance and does not seem to rot.

But then, I have a macracarpa (Hesperocyparis macrocarpa) (also called a Monterey cypress) sign at our front gate. It is soft wood and will soon rot away if left untreated. But, even though I made that sign 18 years ago, it's still perfectly fine and all I do to it is give it a liberal coating of a 50/50 mix of mineral turpentine and boiled linseed oil, once very two years or so. It's almost black in colour now, but strucurally, it's perfectly good.

So, wood can work, provided you look after it or if it's the right type of wood.

MarkJerling Thanks for the information! I use douglas wood, which is made from the Douglas fir https://en.wikipedia.org/wiki/Douglas_fir

Did I make an ok decision regarding the wood?

Cheers!

[MarkJerling]

MarkJerling Thanks for the information! I use douglas wood, which is made from the Douglas fir https://en.wikipedia.org/wiki/Douglas_fir

Did I make an ok decision regarding the wood?

Cheers!

Douglas fir (Pseudotsuga menziesii) is good framing timber but, if used outside in the weather, you'll need to treat the wood regularly to prevent eventual decay. It is, none the less, far better than pine.
Provided you protected the wood with a good penetrating sealer (or my cheap and ancient method of turpentine and linseed oil) it should last many years if regularly recoated.

Remember that an oven is a heavy thing so you need to design your timber base to be cross braced underneath or it will not be a very stable platform before long.

[Mark1986]

Douglas fir (Pseudotsuga menziesii) is good framing timber but, if used outside in the weather, you'll need to treat the wood regularly to prevent eventual decay. It is, none the less, far better than pine.
Provided you protected the wood with a good penetrating sealer (or my cheap and ancient method of turpentine and linseed oil) it should last many years if regularly recoated.

Remember that an oven is a heavy thing so you need to design your timber base to be cross braced underneath or it will not be a very stable platform before long.

MarkJerling I'm going for the 50/50 linseed oil turpentine mix and I'm adding wax to make it more water-resistant. Is that a good idea?

[Mark1986]

Update

So I started building the wooden frame for the pizza oven. I had quite some bad weather so I had to improvise a shelter

The hardest part for me was getting de legs and frame aligned properly. The wood wasn't perfect square and neither were the steel platings that I bought to keep everything fixed in place. Also, the first day I broke the fibre cement board, as I didn't support the cut off piece. That set me back 35 euros. Apart from that, things went quite ok!

I can't seem to upload some of the photos properly. Here is a photo of the end result: https://imgur.com/a/TqELZVK

DavidS Tomorrow I'm going to pour the concrete slab. I'm thinking about wet curing it. Is this a good idea? If so, what frequency, amount of water and total days should I wet cure the slab? After how many days can I pour in the perlite concrete slab?

Thanks in advance!

Cheers

[MarkJerling]

MarkJerling I'm going for the 50/50 linseed oil turpentine mix and I'm adding wax to make it more water-resistant. Is that a good idea?

I would imagine adding a wax can work. Remember to buy boiled linseed oil rather than raw linseed oil. The turpentine acts to speed up the drying and help penetration into the wood thereby helping it become a penetrating sealer. Raw linseed oil can work but takes forever to dry, so boiled works better. Generally a 50/50 mix is good. Also remember that a pile of rags or paper towels soaked with linseed oil can actually start burning without warning, so if you have any oil soaked rags after you done, wet them with water and dispose, wet, in a bag in your garbage or burn the rags in a rubbish fire if that's allowed in your jurisdiction.

[MarkJerling]

Update

So I started building the wooden frame for the pizza oven. I had quite some bad weather so I had to improvise a shelter

The hardest part for me was getting de legs and frame aligned properly. The wood wasn't perfect square and neither were the steel platings that I bought to keep everything fixed in place. Also, the first day I broke the fibre cement board, as I didn't support the cut off piece. That set me back 35 euros. Apart from that, things went quite ok!

I can't seem to upload some of the photos properly. Here is a photo of the end result: https://imgur.com/a/TqELZVK

DavidS Tomorrow I'm going to pour the concrete slab. I'm thinking about wet curing it. Is this a good idea? If so, what frequency, amount of water and total days should I wet cure the slab? After how many days can I pour in the perlite concrete slab?

Thanks in advance!

Cheers

I did warn you to cross-brace your frame. There's literally nothing stopping that design of yours from folding itself up and becoming a folding table! Sorry to be a party pooper but it's a real risk. Once you have some weight on top and a few mates leaning against it things could go South pretty quickly.

[JRPizza]

To Mark's point - if you have or might have any little children around the oven consider adding the cross bracing and making the stand "overbuilt". An oven dumped on it's side would be a bummer - having it drop on a little human would be a tragedy.

[david s]

Update


DavidS Tomorrow I'm going to pour the concrete slab. I'm thinking about wet curing it. Is this a good idea? If so, what frequency, amount of water and total days should I wet cure the slab? After how many days can I pour in the perlite concrete slab?

Thanks in advance!

Cheers

Yes, anything made with OPC will have its strength increased significantly if damp cured. The normal period is 7 days, but some do 28 days. seal the whole slab with plastic wrap.You can then make the perlite concrete (5:1) insulating slab. Because the perlcrete takes so much water in the mix it is not necessary to damp cure it. It will take a few weeks to dry, so wait around 3 weeks before building over it. Vermicrete insulating slab PDF.pdf Vermicrete insulating slab PDF.pdf

Make sure you strengthen the stand. as you've not half checked the timber it can easily move, especially if it's exposed to the weather.

[SableSprings]

Two points from me on your stand (as Mark, JR, & David have already noted above), ...that advised cross bracing is not just important, it's critical for everyone's safety! Also, make sure you allow your table legs to soak up the preservative from the bottom cut faces...it will soak up quite a bit. So if it's possible, dip each leg in a container with preservative & let it soak up for several minutes. Remember that you need to provide a water barrier or air gap (heavy casters) between the wood legs & the concrete floor...even with preservation, that's where the wood will decay first if it's damp/wet.

[Mark1986]

Thanks for the advice on safety! I postponed pouring the concrete and focused on the stand. I couldn't find cross bar easy/fast enough. So I decided to add heavy duty steel corner plating on all sides and I added additional bars 6.5 x 6.5 cm below (see photos). Is this sufficient?

cheers!