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Insulation - Part II

The final stage of insulating my brick oven was to add a layer of cement render, for rigidity and also to support the finishing layer of acrylic-based render...








From memory, I think I used pre-mix cement render bought straight from the hardware store. You could always mix your own render using 3 parts plasterer's sand to 1 part cement (and a cup or so of builder's lime, to aid plasticity), plus water of course, to bring it to a thick, creamy, workable consistency. As with the mortar, a squirt of dish washing liquid gives your render a nice creamy texture.



As you can see, I scored some grooves into the side of the cement render - this was to provide a better support for the final coat. Without something to sit on/grab hold of (especially on the sides of the dome where the surface is steep), the final coat of render could easily slide right off. To score the grooves, I just used the corner of the trowel, or my gloved finger - or probably both! It doesn't have to look great - it just has to do the job.

All told, this penultimate coat of render was about 3cm thick.

At this point (having let the render cure for a 48 hours) I actually fired my oven, just out of curiosity to see how it would fare. It held up perfectly. I noticed a wee bit of expansion as it got really hot. In this pic you can see where a small gap has opened up around where the dome adjoins the chimney...



No big deal - that's how it should behave!

Lastly, I finished the oven with a coat of pre-mix acrylic render from the hardware store. It comes in a range of colours or you can buy tints to make it practically any colour - but I chose a light natural colour, approximating sandstone.

I was in two minds about how to finish this final coat - smooth or textured. I experimented a little as I went, applying it as smooth as possible at first by hand (using a plastering trowel). I then found that rubbing it gently with a damp sponge, using large circular strokes, produced an attractive, lightly textured finish. This photo shows the difference:



Here are some detailed pics of the textured finish:



And that, my friends, was that! Here are a couple of nice pics of the finished oven, taken several years later (and still going strong!)...





6 comments:

  1. Did your oven cracked? Thanks in advance.

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  2. Hi Angelo. No major cracking - a few hairline cracks in the outer render, but that is normal for an oven of this kind. Still very solid and weathertight after several years. I would add some pictures but we have since moved house!

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  3. Thanks Jim, I have been looking to build my own pizza oven, I asked different material suppliers and they told me all the materials I needed but it was getting far to expensive, so I shelved the oven, but the way you have done yours is exactly what I was looking for.
    John

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  4. I'm glad to hear it, John. I also found it hard to get started - everyone trying to sell me something or providing conflicting, confusing or incomplete information etc. It took me a long time to sift the useful info from the dross, make a plan, collect what I hoped were useful materials, and take that first step. It was only as an afterthought that I started making this blog, hoping it might speed up the process for someone. So thanks for the feedback.

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  5. Fantastic blog mate. Reading this in sunny Wales, UK. Been sorting through the dross and thankfully Ive come across this site. Your explanations are brilliant. Been looking for a proper 'how to build a brick dome' for a awhile now.. cheers mate, excellent work

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    1. Thanks, Simon. So glad to hear it.

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