New build - 1.2M dome

[jonv]

Wet weather has delayed further work on the oven, but I've made some progress on the gazebo. Need to put in some corner bracing and board and fibreglass the roof.

[jonv]

I guess it depends on how much insulation you want but with four inches of 128kg blanket I decided that I didn't need a layer of vermicrete. I seem to recall some suggestion that it might be easier to shape if the dome is out of shape somehow, but mine was reasonably round and I fitted the blanket carefully to keep the shape.

I just used sand and cement for both layers, a stronger mix for the base coat. I added a waterproofer to both and also some colour to the top coat - although it has dried so pale that I think I'll paint over it anyway.

It is well worth taking the time to get the shape right on the base coat so that you can concentrate on the finish with the top coat. Initially I thought this would be really difficult but found that by looking at the silhouette as I walked round the dome I could easily see the low/high spots and with surprising accuracy. I would recommend using a sponge to finish as it sets up - if done right and at the appropriate stage, it will take out all the little flats left by the float.

[jas0ny]

Hey jonv, I just layed the mesh wire over my fire blanket. Did you just use cement for the base coat? Or is the perlite/vermiculite mix is the way to go, then put the top coat? What are your thoughts. What top coat did you use by the way?

[jonv]

Started the decorative brickwork... and now have an even deeper respect for the bricklayers who make this look easy. Must confess I found this difficult - it came out ok but took me a long time. If the rain stays away I'll look at the arch tomorrow.

[jonv]

cnegrelli I dug out a photo that shows the break... it's only a small gap so its effectiveness is limited, but it does appear to help a fair bit.

[jonv]

I covered it with a tarp but I'll go wrap it now - thanks for the tip

[david s]

I like to wrap the whole oven in cling wrap for a week to hold the moisture in the outer shell to enhance its strength. Especially as theinsulation is pulling the moisture away from it from the inside.

[jonv]

Managed to finish the top coat today. The colour came out a little patchy and will no doubt be much paler once dry, but I'm inclined to leave it that way. I added a waterproofer to the render but I'll brush over some sealer later just to make sure. Provided it doesn't crack or fall off I'm happy with the render; just need to figure out the brickwork for the chimney now

[jonv]

There's a 10mm gap between the inner arch (the one that's part of the dome) and the chimney stack.

[cnegrelli]

Where exactly did you put the thermal break?

[jonv]

Base coat done - will scratch once it sets up a bit. Was quite nervous of this stage but I'm pleased with the results

Planning to colour the top coat; if I don't like the look once it's dry I'll just paint over it.

[jonv]

Thanks very much for the advice. I can see it would have been a good idea to put the mesh on before the base concrete... I'll just have to fix it to the wires that are holding the insulation in place.

[SableSprings]

...Will get the mesh on the dome soon and then I have wait for a few days of nice weather to arrive to render the dome...

Should I coat the insulation with anything before slapping on the render basecoat?

Try to get the wire mesh on as tightly as possible. You will be cutting wedges to get it to lay down against the dome insulation. The fewer gaps you leave between the insulation and mesh, the less base coat you'll need to keep things "in shape". No need to coat the insulation with anything...it will take up some moisture from the base coat so be prepared for a little quicker drying of the base render than you may expect. The absorbed moisture will get sucked back into the render as it cures and air dries. Anything else in the way of moisture will get taken care of with the next oven firing. Don't forget to scratch the base coat before it dries...the next render layer will need something to grab & hold on to. We used a thin piece of wood (surveyor stakes or paint stir sticks work really well) with some nails pounded evenly through 1/4" or so -- 4 or 5 nails are plenty. The exposed nail points make it easy to pull the stick across the dome and scratch the base render coat. Great job on this and really glad you've been able to use the oven and get some great eats before tackling the "make it pretty" steps.

FYI: if you are intending to put on more base concrete around the dome...it's really nice to embed your wire mesh in it around the perimeter to help secure it while you wrap up the dome.

[jonv]

Back on the job! Just removed the chimney and temporary winter enclosure to start work on the exterior. First task - waterproofing gunk around the insulation and another 3" concrete around the base. Will get the mesh on the dome soon and then I have wait for a few days of nice weather to arrive to render the dome...

Should I coat the insulation with anything before slapping on the render basecoat?

[jonv]

Thanks! I look forward to seeing your finished oven

You're right, the pizza does taste pretty good - I expected the proper flour to make a difference, but what surprised me was the flavour of the genuine san marzano tomatoes. I won't use anything else now. Will watching the dough bubble up and cook so quickly ever get old? I doubt it