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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!)...


  1. Did your oven cracked? Thanks in advance.

  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!

  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.

  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.

  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

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

  6. Thanks for this! I've been reading books and scouring the web. Just like everything else in life, the more you learn the more there is too learn! Do you feel like your oven is big enough? When I look at the footprint mocked up in my yard it is so huge! But then the oven itself is looking to be small.
    Thanks for cataloging all of these steps!

  7. Hi Jo - thanks for the comment! The finished base and oven seem in proportion to me (the finishing render enlarges the dome somewhat). As for the internal dimensions, it's big enough for us, easily accommodating 2-3 12 inch pizzas at a time (I normally only ever cook two at a time since at full temp they cook real quick so you have to be on your toes!). We cook bread and roast meat in it too no worries.