32" Pompeii build Cambridge UK

[CambsPizza]

Thanks for taking the time to look at my 32 inch pompeii build which I have 99% finished.

Firstly a bit of back story as I have no photos of the base etc.

I planned to build a pizza oven when I originally built the BBQ / fireplace and decking area but time, kids and life in general got in the way so the space for the oven was used as a coal cupboard and prep area for the BBQ until I found time to start.

I poured the base when I originally built the BBQ and the rendered walls are dense concrete blocks with raised planters behind them.

I built another concrete block wall and strapped it to the existing between the two retaining walls (pic1) as after reading the forum I was worried about the weight of the finished oven and the span between the walls. I also added a couple of concrete lintels to brace the middle wall (pic2)

I planned to make 3 brick arches to blend the BBQ and oven between the walls (pic3) and added a form to level the arch up to the lintels and external walls.

[david s]

Normally hollow concrete blocks are used so their cores can be filled with concrete and steel. Your solid 100 mm blocks are only held together by the narrow 100 mm mortar joint. Ther is substantial sideways thrust from the large radius arch you’ve built on top. The structure requires beefing up.

[MarkJerling]

I think that, with the reinforced concrete lintels behind, the arch is largely decorative more so than structural. But yes, I agree, that central nib wall is pretty thin as a loadbearing structure.

[CambsPizza]

After the over arch form was poured I used 18mm ply to fill in the voids with temporary bracing underneath ready for the slab. I siliconed round the edges of the ply to ensure no concrete leaked out during the pour. I added steel reinforcement and tied it into the existing block work using steel rods.

I made a template of the finished dome size to work out placement and angle of the opening, but in hindsight I should have added 6-7 inches to the fromt of the slab to allow for a larger oven landing - which I will address later in the build.

[CambsPizza]

I added weep holes through the slab using garden hose with bamboo canes through them to keep them straight and to be able to punch through the concrete once the curing had started. It happened to be a hot day in the UK so I covered the slab with a tarp to keep it from getting too warm.

[CambsPizza]

I wanted to raise the finished level of the oven to above my elbow height so added a layer of thermalite blocks and incorporated a small smoker tunnel that would vent into the dome by removing an internal brick. The piece of paper over the dome template shows where the opening will sit once the dome is built.

[CambsPizza]

Added a layer to broken ceramic tiles to allow any excess moisture to get to the weep holes I have made previously and added 50mm of ceramic fibre board on top of the tiles. The thermailte blocks add enough insulation under the ceramic fibre board to protect the slab so I omitted the vcrete under the oven.

I made a cut out for the smoker vent and lined it with fire brick slivers then started cutting the fire bricks to form the oven floor.

[CambsPizza]

And this is the point I realised I'd made my slab a touch too small as one of the opening walls hung over the front of the slab - a slight problem to be solved another day.

I decided to do a layer of half bricks on top of the oven floor as there is lots of debate on the merits of ontop or outside the floor with no real conclusion that I could see apart from changing broken bricks would be easier in the future if built outside the floor. So onto it is.

I also finished the 2nd decorative arch using the same arch form as the 1st

[MarkJerling]

I wanted to raise the finished level of the oven to above my elbow height so added a layer of thermalite blocks and incorporated a small smoker tunnel that would vent into the dome by removing an internal brick. The piece of paper over the dome template shows where the opening will sit once the dome is built.

Smoker tunnel! There's a cunning plan!

[CambsPizza]

I made and internal arch form and started cutting bricks for the dome while waiting for a bag of fire clay to arrive.

I also completed the middle arch and rendered the base slab.

on a side note, my grape vine was starting to grow very quickly which I hadn't factored into my plan for insulating the dome - but more on that later.

[CambsPizza]

I removed the central brick and made a simple indespensable tool - caster set into a wooden brick set into the floor. I covered the floor with some thin ply to protect it during the build as it gets messy fast. I used used the homebrew 3:1:1:1 (sand, cement, lime, fireclay) mix to start placing the half bricks round the edge of the dome.

The first course is only has mortar between the bricks not onto the floor to allow for thermal movement of the floor.

[CambsPizza]

Got to the arch after reading many, many threads about it but by that point it kinda, sorta made sense and the cuts lined up so I just trusted the IT and carried on.

[CambsPizza]

Had a tidy up of the inside of the dome, the bricks for the dome were all reclaimed from a barrel oven a friend had when he moved into his new house and removed when he remodelled his garden (which saved a fortune in bricks) but I had to remove a tonne of homebrew from the bricks before cutting them (which took ages to do)

I have included a picture of the smoker vent with the removable brick removed from the inside and you can see the lump on the outside over the ceramic board where the firebrick shims cover the vent opening. I know this could be a source of heat loss but I'm planning a good amount of insulation over & around the dome.

I moved onto using stick props for the bricks once I passed the arch and started doing full rings, using smaller bricks and trying to taper them to get a close fit. I used my 9 inch petrol stone cutter for every cut so not as refind as a brick cutter but it did the job to my satisfaction - its by no means perfect but it does the job.

[CambsPizza]

Finished the dome (got excited to be done and didn't take and photos - I will take some later and upload them) then slathered the dome with a layer of home brew to fill in any gaps to the outside of the dome and added our initials and the date on top.

I then added 2 layers of 25mm ceramic fibre blanket over the dome so it sat on top of the ceramic board, which I cut bigger than the brick dome ( see previous photos)

[CambsPizza]

Wrapped chicken wire tightly over the insulation blanket and made a vcrete mix, after a bit of trial and error I found 9 parts vermiculite to 1 part cement plus a handful of fire clay to 3 parts water gave a good workable mix (I added one part water to the dry vermiculite and used a hoe in a mixing bucket to moisten the vermiculite then mixed the clay and cement separately using 1 part water and poured it over the wetted vermiculite, then the final part water to clean the cement bucket and pour over the cement mixed vermiculite trying not to wash the cement off the vermiculite) the mix worked quite well and mostly stuck where I put it.

The hardest part was getting access to the rear of the dome as the grape vine was sprouting tendrils everywhere at this point so some selective pruning was undertaken. I also only had 100mm clearance between the grape vine support posts and the rear of the oven so I had to hand stick the vcrete (I lost quite a bit of it using this method) rather than building up in layers.

I also added a vent at the top of the dome to allow excess water to escape during the curing process.