Homebrew Castable 650mm East Sussex UK

[bamforp]

This is my second build and it is going to be largely the same design as the oven I built for my son and daughter in law which I documented in this thread - https://community.fornobravo.com/for...ble-21-kent-uk

I have made a few changes to the design, most noticeably the oven diameter is 650mm vs 600mm and I have added a beer shelf. The oven is set into a sandstone bank at the side of our property so the first step was to build a small reinforced concrete footing and start to build up the brick courses, tying the brickwork into the bank as I went. I am using the same technique for the oven base i.e. aerated concrete blocks glued together with construction adhesive and resting on concrete lintels. The photos illustrate progress after a few days work.

[bamforp]

During the build of the base I decided to add a couple of extra brick courses as it made it easier to match the contours of the sandstone but after sleeping on it for a couple of days I decided the oven floor was going to be way too high so out came the big hammer! I mention this mainly because in the process of removing the aerated blocks it became clear just how strong the construction adhesive bond is - in most cases the blocks split rather than the adhesive bonds. Anyway, I excavated out a bit more of the sandstone and decided to rest the rear of the blocks on the sandstone levelled off with some concrete pads. I want the oven to be isolated from the bank from a damp perspective so there are some drainage channels between the pads and the blocks are resting on damp proof membrane. Once the base was finished I laid the fire bricks on a thin layer of moist sand to level them out.

[bamforp]

The shelf was made using lengths of 6mm tile backer board glued together and glued to the top of the aerated concrete blocks. I constructed some simple formwork and cast a 4:1 vermicrete layer and then finished it off with terracotta quarry tiles and a decorative tile border. It was a bit of an experiment but I am very happy with the result - it is rock solid already and it will also eventually have the flue casting sitting on top of it to further anchor it. The sand mold for the oven dome was straightforward and once again I used formwork and tools made out of 50mm polystyrene insulation board wrapped in packing tape to seal the edges.

[bamforp]

A final post for now with photos of the homebrew dome casting. As with my son's oven, I made a 'weak' joint towards the top of the oven with some wet newspaper before finishing the top of the casting. The dome is now wrapped in clingfilm to reduce moisture loss as I turn my attention to the flue casting.

[bamforp]

Some more updates on my second build but apologies that the photos are not in sequence - I have not worked out how the forum software sorts uploaded photos. Anyway, I removed the dome moulds and sand/bricks etc from the dome casting after approximately 36 hrs. On inspection I would say the internal surface is not quite as smooth as my first build but there was nothing that caused me any concerns. There are lots of close-ups of the surface in the photo album linked in my signature if anyone is interested.

I moved onto constructing the mould for the flue gallery. I had spent quite a bit of time playing around with Google Drawings to check I could fit a 65cm dome on the same base footprint that I used for the 60cm oven and decided I needed to push this flue gallery back by 50mm compared to the 60cm oven. This was easy to achieve with a bit of sand between the foam mould and the dome casting and it worked out really well. I also reduced the flue gallery wall thickness from 50mm to 35mm to reduce slumping which had been a slight problem on my first build and it certainly helped although I still got a bit of slumping on the front vertical surface which needed a bit of propping up. I used the same approach of casting a stepped shelf at the top of the flue gallery to support the stainless steel flue pipe which then gets back filled with a bit of 5:1 vermicrete to secure it.

[bamforp]

Once the flue gallery mould was out I did a trial fit of the flue pipe and front arch as shown in the 4th photo - you can also see the holes that will vent the insulation layer into the flue. The ceramic fibre insulation came next followed by the 10:1 vermicrete outer layer. I learnt from my first build that the vermicrete will just drop off any vertical/near vertical surfaces so I spent a bit of time putting together some formwork from old carboard boxes and proceeded with the fill. It went pretty well and it is easy to carve off any stray bits after 36hrs to get to the shape you want. I have a short length of terracotta chimney that I salvaged from an old chimenea that I am going to use to cover the stainless flue for purely cosmetic reasons and I am now about to start the slow dry out phase.

[bamforp]

I have made quite a bit of progress on my build so I thought it was time for an update. Once the vermicrete layer had had a chance to firm up I added some tiles around the arch and then rendered the oven using the Weber one coat render product I had used on my first build at my son's property. It was a full day's work but I'm happy with the result and I remembered to use some decent gloves this time as the product is pretty aggressive on the skin. I just need to paint the oven now with some decent masonry paint but we have already started to the use the oven for a couple of cooks. I need to raise my pizza dough game but it's been great fun learning how to manage the fire and how to make the best use of the oven. Some cracks have appeared in the dome, the most obvious being directly opposite the mouth of the oven but they completely close up once the oven heats up - I suppose the dome has just created it's own natural expansion joints. Perhaps using stainless steel needles might have helped but none of the cracks are giving me any cause for concern at this stage so I don't know if needles are worth the hassle/expense.

[bamforp]

Besides all the usual pizza peel and brushes paraphernalia one item that has proven vey useful so far is my diy Tuscan grill. My neighbour helped me weld it up using 12mm rebar which I cleaned up with a wire wheel and seasoned with vegetable oil. I sized it so that the centre grill from our Weber bbq sits nicely on it and it can also accommodate a cast iron skillet or pan. It also works well as a support for kebab skewers so it's proving very versatile.

Anyway, overall it's been a very enjoyable summer project that has kept me out of mischief! I do have 22 fire bricks and some other bits and pieces left over which I will put on a separate post in the buy/sell thread in case anyone near East Sussex is interested.

[david s]

That’s looking very nice.

[bamforp]

Thanks Dave, and thanks again for so generously sharing your knowledge on the forum - I have learnt a lot from your posts.

[MarkJerling]

Besides all the usual pizza peel and brushes paraphernalia one item that has proven vey useful so far is my diy Tuscan grill. My neighbour helped me weld it up using 12mm rebar which I cleaned up with a wire wheel and seasoned with vegetable oil. I sized it so that the centre grill from our Weber bbq sits nicely on it and it can also accommodate a cast iron skillet or pan. It also works well as a support for kebab skewers so it's proving very versatile.

Anyway, overall it's been a very enjoyable summer project that has kept me out of mischief! I do have 22 fire bricks and some other bits and pieces left over which I will put on a separate post in the buy/sell thread in case anyone near East Sussex is interested.

I really enjoyed seeing your rebar grille stand. Very cool.

[bamforp]

Thanks Mark, it's proving really useful and cheap as chips as we say in this side of the pond.

[MarkJerling]

We use that expression down here as well!

[Uzzzman]

A final post for now with photos of the homebrew dome casting. As with my son's oven, I made a 'weak' joint towards the top of the oven with some wet newspaper before finishing the top of the casting. The dome is now wrapped in clingfilm to reduce moisture loss as I turn my attention to the flue casting.

hi - great work! Newbie here - what’s the benefit of the weak joint? Control crack essentially?