Help with woodoven

[Cheezy]

I know it's trendy etc since JOliver flashed his big one on the TV, however I've wanted to build one for ages, I make all my own bread etc, and will use it in place of firing up the cooker...in theory. My design will also double up as a cold smoker and BBQ. See I'v e spent some time on it ....at work anyway:lol:

From reading t'internet guff I think I'm going to get refractory 2" bricks, I've worked out how many etc.

Heres m' questions
1. Do you know if refractory bricks are frost proof, are they OK to leave uncovered in our weather (ie what if it starts to rain when I'm baking?)

2. Should I put a covering of say lime wash over them to weather proof them.

I'm thinking of putting a lean to roof over the oven .


3. Mortor. My usual mortor is 5 parts sand 1 part cement 1 part lime (it gives a colour close to the victorian mortor that my house is built in. And I like using lime as it gets harder over time)

Will this be OK for a wood oven, or should I use fire cement. And is Fire cement OK for use as mortor...same question in reverse!.


Any help appreciated, especially as I'm going to try and build it next week!

[marshlander]

Can't remember whether fire bricks are frost proof - I doubt anyone will guarantee it as they prolly wouldn't have been tested for water absorbtion or strength - they're designed for indoor use only. Unless you've got a source of free bricks they would be a bit expensive to use in areas you don;t need to anyway - double the price of a good stock brick. So use fire bricks for the inner skin and good stock bricks for the outer. Don't use flettons.

Ideally you would use refractory mortar. All mortar is heat resistant to a point, but refractory mortar is a lot more durable/resistant to heat than simple portland cement mortar.

It's used mainly for jointing flue liners and it's available from builders merchants in cartridges for a mastic gun and big buckets that you mix up yourself. or at least it was -I've been out of the industry for years now!

Another alternative, if you are not stressed what it looks like, especially if it's on the inside is to improvise with refractory concrete items sold for fire place and flue construction. Dunbrick is one mfr and they can tell you where their stockists are.

If you just want a simple mud oven see here http://www.permaculture-magazine.co.uk/ ... le_31.html

I've just remembered that Brick Development Association which provides some guides - very broing unless you're interested!
http://www.brick.org.uk/_resources/A%20 ... ORTARS.pdf is about mortars

Ibstock brick publish some excellent downlaodable guides to brickwork -walls steps and so on http://www.ibstock.com/portal-literatur ... asp?pNum=5

[contadino]

I'm not sure what your design looks like. If you're after the traditional domed oven with the chimney at the front, you'll probably find that you don't need a BBQ as you can cook quite easily in the oven instead. I use one of those clamp-type grills for meat and just position it over the embers.

Refractory bricks are the way to go for the inside. AFAIK, they're not frost-proof, but it won't get frosty inside the oven as the outside will protect it (plus, I presume you'll have a metal door on the front.)

Lime mortar will work, but better would be something that's called gesso here. I'm afraid I don't know what it's called in English. You'd be wise to put a layer of a minimum of 2 inches of gesso and a fire blanket above the dome before you start building up the external mass.

You're better off not using refactory bricks for the entrance archway as they're not that hard and will start to get chipped by the branches you bung in the oven. Something harder would be better - and the temperature at the entrance is much lower.

[tiggy]

Building a wood fired oven for bread and pizza by Tom Jaine. this book gives plans and materials list also lots of background info on wood fired ovens. also includes advice on running the oven and on the tools used.We havent got any further than reading the book so i can say no more.Good Luck

[Cheezy]

Many thanks everyone. I've done a bit of research and I'm in two minds.

There are two designs. One is a clay (or modern equivalent) dome, the other is the free standing fire brick dome insert with traditional brick outside.

I was thinking of doing a hybrid (ie I didn't want to fork out and buy the external bricks.!)

So I was going with the firebrick insert (domed) with the chimney at the front, also as Contadino say's doubling up as a BBQ, then trying to cover the outside of the bricks with something to keep the weather off and add additional insulation.

However I had forgotten about the massive expansion and contraction that's going to be going on, and any covering of the firebricks (unless its very flexible ) is going to crack straight away.

I'm very limited to the size as well so a double skinned oven is going to be difficult to fit in.
my maximum depth is only 60cm!, but my width is vertually unlimited (i'm building against my house the back of where the chimney is.)

My next door neighbour has offered me a load of blocks he has taken out of electric storage heaters (yes he's a worse hoarder than me, he's had them 17 years!!!), these would make a great second skin, but they're just too thick for the limited area.

Current thinking is build the insert 2 bricks wide (approx 50 cm), 1 m long, leaving a gap between my external house wall and the insert to fill with a fire blanket or vermiculite etc. Build a small entrance out of std brick , including a chimney between the insert and entrance.
If I can find some cheap reclaimed bricks I could use them for the second skin leaving a gap to be filled with fire blanket/vermiculite, if not I thought about thermolite breeze blocks with a lime wash finish.

Contidino, you mention a door, I hadn't thought one was necessary ( i have used wood ovens in Italy and can't remember them having one.) If you put one in (and I can understand why you would have one.) where does it go. Before the chimney (against the insert) or at the front of the entrance?.

[contadino]

The door closes the domed part off before the flue. You don't need a door if you're cooking pizze, because they're cooked when the oven is really hot. If you want to make bread/foccacia/any other 'al forno' food, you'll need a door to a) keep the heat in, and b) change the wood to charcoal (otherwise everything will taste smokey.)

[contadino]

The outside skin doesn't need to be brick. You can fill with rubble (stone is good, but I suspect those storage heater bricks will be even better) and use stone to dress it.

When you say depth, do you mean the distance from the front of the flue to the back of the oven? 60cm is IMHO not enough. Could you build it side on, so it's not as wide but deeper? I've seen oven domes which work well.

[caithnesscrofter]

Just noticed this thread today. I've helped build ovens before and am actually building one at the minute as we are working on an outdoor kitchen. The ones I was taught how to build are like the ones in Kiko Denzers book. I'm using old storage heater bricks for the floor of this oven....



The photo below was taken just yesturday. It is of the finished sand form that creates the oven void that we cobbed over last nite. When it dries, we cut the door and scrape out the sand.



We will put another layer of cob on in a few days then plaster with a litema (clay & coopoo)

The whole thing will have a roof on eventually. Highly recommend kikos book. Cost of oven = £0

This type of oven you start the fire inside and let it heat up then scrape out the entire fire before you bake in it. Ovens inside diameter is 27 inches but, can be any size really. Proportions between internal radius, height and door size just need to be maintained. It can have a chimney or not. Good luck on your oven.

[Cheezy]

Thanks Caithness and Contadino. Again now in two minds!

Caithness, I had thought about clay/cobb type, but I'm a townie and don't have easy access to clay (except down the lottie, but it's more silt/clay than pure clay, and it's 2ft down!)
I do have a large heap of cow manure down the lottie, mixed with straw...would this be anygood!! (it is well rotted as I got it last year)
Nice pics btw, if I were to make one like yours it's about the same size I would be looking at. Approx how much cobb do you need for that size?., How thick?.

With the extream heat does the cobb oven not show a lot of cracks? And what do you do about them. Can you fire it up if it's raining?

Do you think I could build the internal dome out of heater storage brick (which are free!)?

Contadino , I could turn it on it's side , but I thought if it was narrow front to back, compared to wide at the sides I could brush my embers to the sides while cooking in the middle.

I'm going to keep on researching, as at the moment my builders finally turned up to replace the kitchen roof, and is using my oven base as a wood storage area!.

[caithnesscrofter]

Hey Cheezy,

If you've got access to subsoil at your lottie that should do. Don't worry, you don't need pure clay, you are looking for a good clay/sand mix. For an oven the size of mine for the first layer you need roughly 3 full wheelbarrows. This layer is 3-4 inches thick. Use the width of your hand as a guide. No straw goes in this layer.

I've fired mine 3 or 4 times now and maybe one or two hairline cracks have appeared on the exterior. These cracks don't go all the way through. The cracks don't matter so much anyways as there is another layer of cob to go on too. What you can do if you get some cracking is to mix some of your subsoil really wet in a bucket then add extra sand. Rub this mix and fill in the cracks with this. Too much clay in the original mix for the stove causes alot of cracking. If you get the right ratio you will have little cracking.

Sure, you can fire up in the rain. Once it's fired up for 20 minutes the outside will be so hot that the raindrops dry on contact.

I suppose you could build the dome with bricks. Never tried it. I think cob is easier tho if you can get subsoil.

I will post a photo of the dome when I get one on the computer. Good luck.