38" Pompeii build

[david s]

Your build is going exceptionally well. the elevated insulation will help the drying process. If you can, expose the project to sun and wind to allow ir to do nost of the drying for you. Failing that perhaps set up a fan.

Chexk out my insulation drying experiment here.

https://community.fornobravo.com/for...098#post458098

[JRPizza]

Looking good! I had a similar shelter malfunction and got my floor bricks and insulation soaked. After that they were covered for months but still held lots of water till I did my slow drying fires.

[UtahBeehiver]

For not having a wet saw, you floor bricks look great. Search for "taper inner arch" on the blog, there are dozens of examples of arch and dome interface. It is the best way to form a effective tie of inner arch and dome.

[Frenchie]

Progress has been slow, my temporary shelter blew away in a storm and the insulation board got soaked.
I presume the board will be fine (calsil) so I’m cracking on regardless.

bottom course of dome is mostly down and have nearly finished cutting my inner arch bricks. (I wish I had a proper wet saw)

all the bricks are the same, per the sketchup model. I presume this is a function of a semi-circular arch intersecting a hemispherical dome.

Skill level is zero, it is not beautiful work, but it will cook pizza. At this stage I’m just enjoying it and not stressing over perfection (or anything close)

[Frenchie]

Cut the floor bricks at the weekend, and arranged some half bricks to see first hand the gaps formed by not tapering.
I also started on the first level of arch brick - I have tapered bricks to form the arches so those will be some interesting cuts with the 9" grinder...!
I really see the merit of a wet saw now, and I am considering renting one for a few weeks.

Next step is to position the inner arch form and mark its position on the floor (I may even screw it down through the shims). Then I will re-cut floor brick adjacent to the left had arch brick as something has gone out of whack (grinder is an agricultural cutting method especially for internal angle cuts!) before starting on the inner arch.

I have modelled the semi-circular arch intersection with the dome several times and cant get away from concluding that my arch bricks are all identical. Is this a function of a semi-circular arch or is it some miracle of geometry? In line with all other advice on this forum I was expecting the tapered arch bricks to differ as we go up in height.

[Frenchie]

These projects do get put on the back burner sometimes, my own did when I had to move halfway across the country for an extended bit to take care of my in-laws.

Glad to see you back at it.

Step-by-step.

Thanks mongota, step-by-step as you say. Now I'm getting on with things I am reminded why it was such slow going last time - doing anything for the first time comes with a degree of trepidation, and all of this is new to me!

[mongota]

These projects do get put on the back burner sometimes, my own did when I had to move halfway across the country for an extended bit to take care of my in-laws.

Glad to see you back at it.

Step-by-step.

[Frenchie]

Made some progress yesterday now the rain and wind finally cleared off!

Cut the floor insulation - in the end I used a 6" drywall jabsaw which was handy. My jigsaw shoe has gone out of alignment so it makes a mess of things. I'm very glad to have this job out the way, the cleanup was arduous and it means I can get on with laying brick!

Mocked up the floor - I laid out the bricks on my template in a herringbone and marked the centre of the pattern (the true centre of a herringbone goes between the two lines of points, and not on the points themselves). Then I drilled and plugged the centre brick to mount the IT and scribed the outside diameter of the floor (initially I got the dimension incorrect, so you'll see two diameters - ill be cutting to the inside one).

Then I put my mosaic tiles on the oven floor where I had marked out the outline of the oven. Some of the tiles had gotten wet over the winter and the backing mesh has discoloured - this won't matter as they just raise the calsil off the slab and provide some drainage channels.

After that I laid the calsil sheets (3x 1" thick layers) on the tiles and marked out the centre of the oven (relative to the foundation) on the calsil. I cut the calsil about 5-10mm in any dimension larger than it needs to be to account for positional tolerance on the foundation.

Finally I transferred the bricks from the mock-up on the template to the calsil, starting with the centremost brick (with IT attachments) and working along the centreline initially.
I think, theoretically the oven and insulation should now be centred on the slab per design.

I had a go at bolstering some bricks. Made a quick jig using scrap materials as I will be cutting a lot of halves, scribed a line around 4 sides of the brick and tapped each side before giving a good hard crack to break the brick on one of the wide sides. This worked remarkably well so I am happy to continue bolstering the dome bricks.

For the neater cuts, around the perimeter of the floor and for the arch bricks, I will use the 9" grinder with the 2mm thick diamond blade.

Given autumn is closing in on us, need to get a move on here.

Open to suggestions! thanks all

[Frenchie]

I have finally cut my templates for the fibreboard and brick floor, and have marked out on my slab where the oven will go and on the fibreboard marked up the cuts.

some questions when thinking about next steps;

1) what is the best way to cut calsil (1”)? I have a jigsaw and all the PPE but is that too aggressive

2) is it an inconvenience or a showstopper if the calsil gets wet during construction? It might take several more weeks and have only a tarp to cover things

3) is there anything between the floor bricks and the calsil? A screeded layer of sand&fireclay?

4) has anyone experience using the Vitcas range of materials for cement & mortar - are they any good? If not what would be a good choice in the UK?

5) for cutting the firebricks, will 9” grinder do for the more detailed cuts? I plan to bolster the halves for the sake of my neighbours. On that note, are there any great tricks to know for bolstering fire bricks?

thank-you, hope to provide some picture updates for you once some more tangible progress is made!

[MarkJerling]

Welcome aboard Frenchie! Looking good so far.

[Frenchie]

got a cool component for my IT, it’s a tiller extension hinge for small sailing boat. £20 delivered

[Frenchie]

Hello, thanks Russell for your detailed response about the tapered arch bricks - i've finally (after nearly a year) got my head around it!

Only joking, it didn't take a year but life got in the way of this project in quite a large way and I'm just getting back into it now. Pleased to be back!

Progress is as per the photos from last year, suspended slab is ready for building the oven. Therefore in readiness to cut templates and start cutting materials, I wanted to check in with the experts and see if my plans stack up.
I have revisited the arch design; we prefer the look of a semicircular arch so this version is around 22" wide and 12" tall.
Considering the internal dome height is 20", the ratio is approximately 60% which should be ok?

WRT the arch design itself, I am opting for a heat break, therefore will be building 2 distinct arches; the first that intersects the dome and a second which supports the chimney/flue. The second arch is 1.5 full bricks long, so I can use half bricks each side to create the flue gas opening on top. The outer arch looks to me quite long, but to be honest I don't hate the 'long tunnel'. If there are practical issues here let me know and I could use 1 full brick overall length, creating the opening using 1/4s or 1/3rd bricks instead?

In between the flue-supporting arch and the dome-intersecting arch will be stuffed (and backed with gasket sealant) fibre rope.
Loads from the dome and the outer arches are therefore decoupled. This raises the question; is that a problem? From a thermal load perspective I suspect not, but structurally, will the outer arches support the flue sufficiently? I am worried about overturning caused by side loads on the flue, e.g. wind, or an adventurous child perhaps. Is it good practice to tie back the outer arch to the main structure?

Thanks in advance, cheers all (pics / plans attached I hope)

[UtahBeehiver]

If you are doing what is called a "tapered inner arch" (recommended) the you start with "FULL" bricks which are cut using info from your IT. Search the blog, there are dozens of examples. Caveat Emptor, this is one of the most difficult concept to visualize but not too difficult to execute as long as you are patient. The 63-66 inner arch ratio is a rule of thumb, good to shoot for but not a deal killer if you are off a little. I have at couple pics to get you started. The tapered inner arch is used on both full arch and axe arch.

[Frenchie]

Inner arch design!

My original plans were not optimal for incorporating a heat break. So, now I will have effectively 3 arches;
1) inner arch intersecting dome
2) Inner entry (and flue supporting arch) - butted up against inner arch via fibre rope
3) outer arch (and flue supporting)

For the innermost arch:
If my dome is built with half bricks, should this also be built with half bricks?
Is the distance from the centre of the oven to the inside face of the inner-most arch a function of arch height or arch width?
If creating a semi-circular arch, I presume radius is taken as 63% (thereabouts) of dome height?
If creating a truncated arch, with straight side walls, how is the radius chosen, while observing the above ~63% rule? Is it purely artistic?

There are so many variables for this critical part of the design, I don't wish to be integrating dome and arch on 4th course and realise a monumental error!

Thanks in advance for your pearls of wisdom. Always appreciated

[Frenchie]

Thanks to everyone who has offered advice - this project constantly reminds me to check before I act having made a couple of mistakes.
Anyway, all is well with the suspended slab, I think.

It isn't super tidy, but there is rendering and tiling to be done so I am not fussed. Besides, faults and imperfections have stories

Anyway, it is fun to share pictures so here is a micro-blog update.

Digging out the slope; My garden is on a hill and I have heavy clay soil. I excavated enough to find a level and put down 8" of compacted MOT type 1 aggregate. Done by hand (well, shovel and mattock).



Then the form, sheeting and steel reinforcement for 6" slab. It measures 6m x 3m



Then after pour and screed bar (pumped mix was a back-saver. Anyway, off to the pub):



Some months later, blockwork and formwork for suspended slab:



Reinforced, with plastic tube set in for weep holes:



And another broken back later: (I sustained quite bad cement burns and am scarred from getting mixture on me while lifting and pouring buckets of cement. The irritation and discomfort I thought was abrasion but was an alkali reaction as the stuff soaked through my clothing and stayed on my skin for about 4 hours. Be careful!)





Next step I have my mosaic pool tiles as a sub-layer. I am making a template to cut calsil board and tiles to match. Upcoming question: