Home brew oven on an oak base - Warwickshire UK

[Matts]

Hi, I have been lurking here for a couple of years quietly planning my oven and am finally getting started so I thought it about time to share my build.

Most of my inspiration and ideas have come from here so thanks all for sharing your builds and knowledge.

My plan is for a 800mm (32in) is oven made from home brew castable, with ceramic blanket, vermiculite/pearlite and then render.

Not decided on the final finish, I like the look of the broken colourful tile finishes and will most likely build a small roof for the oven.

For the base I have some 63mm fire bricks which will sit on a ceramic fibre board, I am building the stand out of oak and using concrete lintels to support the base.

I have been wanting to build an oven for years but have always had other priorities, renovating our old house, garden and now two kids. It’s great to finally get started on the project although I suspect progress will be slow, I will try to post a few pics of the base so far.

[Matts]

Here is the base going up, I enjoyed a good few winter evenings chipping away in the garage making this. Eventually we will have worktops on both side of the oven too.

[UtahBeehiver]

Wood base do have a tendency to move and expand but that said I got to give you an A plus for your skills in timber wood craft. That is some nice joint work you have there.

PS - Nick JC from the UK did a very nice cast oven with an overhead roof. His thread my help you with materials and construction. Also, David S is our resident cast expert for reach out to him for details questions.

[Hamilton]

Really cool.
Is the base bolted together or pinned with wooden pins?

[Matts]

I’m sure it will move a little over time but I’m happy to take that risk to avoid using too much concrete. I thought about using the more traditional concrete, blocks and more concrete but I prefer the look of oak and I keen to avoid too much concrete.

So far it’s all pegged, nothing more than oak and linseed oil to finish, that will change when I get the lintels and base in.

I do have a few questions that I have not been able to answer by reading the back catalog of builds on here:

I have a few bags of NHL5 lime left over from a floor we laid, is this ok for the home brew mix or do I need the hydrated lime you get from normal builders merchants?

How essential is a 6” flue on a 32” oven? Can I get away with 5”? The reason I ask is there is a good looking on sold by vitcas which looks ready made for an oven.

thanks
matt

[fox]

Those vitcas flues are only 100mm (4”j you can get away with 5” on a 32 but an insulated 6” would be a lot better.

[Matts]

I made a bit more progress on the base, now trying to decide how deep to make the gallery, one full brick feels about right, and is easiest to do.

Thanks for your comment fox, I had not thought about insulated flues, 6” insulated is going to be really big bit if that is what it needs I’ll work out how to fit it in.

[fox]

You dont have to use a double wall insulated chimney but that is what I fit to all my ovens, an insulated chimney will encourage maximum draw but a standard 6” flue will work ok.
I would make the gallery as short as possible and the chimney diameter is often the governing factor.

[Chach]

Keep in mind if you ever plan on enclosing the oven at all a double wall needs minimal clearance to combustible material where as a single wall needs a lot more clearance to combustibles. Now this may not apply to your build but I just felt others should know that a single wall flue is not an accepted practice for enclosures since it needs 18" of clearance to combustibles where as double wall is only 2" clearance.

Ricky

[david s]

If it falls under the building code it is illegal in most places to have a single wall penetrating a ceiling or roof.

[Chach]

If it falls under the building code it is illegal in most places to have a single wall penetrating a ceiling or roof.

100% agree!

[Matts]

I got the dome cast today, the sand castle was easy to build, very neat with a shaped form to keep an even profile all the way around.

Not sure if the newspaper was worth the hassle, hard to get on, kept drying out and blowing off, then was moving around as I put the homebrew on.

I mixed the homebrew as dry as I dared, it went on by hand nicely, a little slumping but nothing significant, then I floated it smooth and finished with a wooden float to keep the finished surface a bit more open to vapour.

Now it’s all wrapped up with a few blankets as it looks like being frosty tonight.

I will see how form it looks tomorrow and maybe start removing the form and sand.

[david s]

Nice job. Don't worry about the newspaper, it's only purpose is to provide a nice smooth surface on the inside and to stop the castable from picking up sand. just give it a really good scrub with a stiff scrubbing brush to avoid dropping sand on your pizza. The newspaper, if any remains stuck in the castable, will just burn away. Wait at least two days before removing the front plate and the sand before filling any of the voids on the inner surface. Holding moisture into the casting for at least a week will enhance its strength so once the voids on the inner surface have been filled cover it with wet hessian or similar and seal it all up.

Not sure how big your oven is, but it will be heavier than you think. If those galvanised truss ties are all that are holding the weight of the oven, you should have a couple of decent props in the centre of the stand to support the oven's weight.

[Matts]

There are six joist hangers for 4x8 joists, each is rated for a few hundered kg static plus dynamic loading you get with floors. The oven will be 4-500kg at best so won’t trouble the base.

[david s]

I hope you’re right. Most ovens sit on a 4” thick reinforced concrete slab, which, depending on how much weight it has to support, may be overkill, but remember that the strength of a slab is directly proportional to the square of its thickness. Thus, a 2” thick slab will be 1/4 the strength of a 4” one. That is a full slab, not three lintel blocks. No idea how thick your lintel blocks are, what the span is, or what sits between them and the insulating board, but it looks to me, from just viewing the pic, somewhat on the light side. Reducing the span by cantilevering or adding additional piers under the centre might be prudent.