Waterproof render mix Pompeii Oven Construction Discuss Waterproof render mix in the Pizza Oven Design and Installation forums; Any advice on what mix to use for the dome render please. Should I use sharp or soft sand, and ...

[shepster]

Any advice on what mix to use for the dome render please.
Should I use sharp or soft sand, and should it have lime? Is it necessary to add waterproofing chemicals? I want to have it as an external finish so may paint it as well. Does it need any chickenwire etc.
Thanks
Shepster

[Rodneyf]

Good questions and we are both waiting for the replies. It seems we are at the same stage of our builds and need help with a final finish.

[david s]

There are many opinions on the make up of the mix. A mixture with a fair amount of lime is apparently slightly elastic which should be an advantage. I use 4:1:1 soft sand,lime,cement. I used to use chicken wire, but now use fibre reinforcing and I make the layer about 15 mm thick. Leave it for about 10 firings before waterproofing, because it will continue to expel water for quite some time.

[Rodneyf]

What do you use as a waterproofing agent? Can you colour the water proofing or do you colour the first coat?

[shepster]

Fibre reinforcing eh? Have not seen that before. Anyone know about it in the UK and if so does it have a trade name and do I have to buy a 100 metre roll!!!?
Shepster

[david s]

fibre reinforcing is used widely as a replacement of steel in concrete. See your local concrete supplier. For waterproofing an acrylic render works well. Because it is flexible it will deal with any fine cracks in the outer shell. I find the easiest way to apply it is to thin it with water and paint it on in a number of coats until you have a layer of about 2-3 mm thick.

[Neil2]

Consider using acrylic stucco.