Post by downunderdave on Jul 7, 2019 21:12:29 GMT
The outer shell is just a covering to keep out the weather. Traditionally Italian ovens were finished with a lime based render which is porous. This is ok as it will keep oout most of the moisture from entering. If the outer shell is made completely waterproof then it also holds moisture in making drying more difficult. A lot depends on the climate you live in. We live in the tropics and only in our wet season is having a wet oven a problem. Because it’s so hot we just don’t use the oven much then anyhow. I have noticed that in really humid weather the oven picks up considerable moisture from the high humidity during those times even if it hasn’t actually rained. In that case an impermeable coating doesn’t keep out the moisture.
I think therefore that the best solution is to have a porous outer shell with a roof over it, but this of course involves extra labour and expense. Another alternative is to build an enclosure style that is popular with the Americans, but again is extra work and expense. A cement shell sometimes cracks which is really ok but does provide both an entry and exit for moisture.[In any case I think it is a good idea to provide a release for steam pressure as this can cause the shell to crack, like a hole in a saucepan lid works.In my design moisture can find its way out via a vent surrounding the glue pipe. ]My solution is to paint the outer cement shell with a flexible acrylic material that covers any cracks and creates a waterproof finish. I use a product called flexible pointing which was developed to seal the ridge caps on tiled roofs. As it’s designed to be troweled on I water it down 20% and paint on 3 layers resulting in about a 2mm thick coating. An alternative could be an exterior 100% acrylic render, but I’m not sure it’s as flexible as the flexible pointing. Apologies for the long winded answer.
I think therefore that the best solution is to have a porous outer shell with a roof over it, but this of course involves extra labour and expense. Another alternative is to build an enclosure style that is popular with the Americans, but again is extra work and expense. A cement shell sometimes cracks which is really ok but does provide both an entry and exit for moisture.[In any case I think it is a good idea to provide a release for steam pressure as this can cause the shell to crack, like a hole in a saucepan lid works.In my design moisture can find its way out via a vent surrounding the glue pipe. ]My solution is to paint the outer cement shell with a flexible acrylic material that covers any cracks and creates a waterproof finish. I use a product called flexible pointing which was developed to seal the ridge caps on tiled roofs. As it’s designed to be troweled on I water it down 20% and paint on 3 layers resulting in about a 2mm thick coating. An alternative could be an exterior 100% acrylic render, but I’m not sure it’s as flexible as the flexible pointing. Apologies for the long winded answer.
