Does waterproofing stop water getting out as well as in?? Design Styles, Chimneys and Finish Discuss Does waterproofing stop water getting out as well as in?? in the Pizza Oven Design and Installation forums; I've just got to the stage of having a cured oven (5 fires built up over 6 days) covered in ...

[johnfisher]

I've just got to the stage of having a cured oven (5 fires built up over 6 days) covered in blanket and vermiculite and with the first real cooking due on Saturday (and heavy rain on Sunday onwards) I was hoping for some advice on waterproofing.

My plan was to not render the oven for a few weeks while I cook in it, and to cover it with a tarpaulin when not using it to keep the rain out. However there are threads here about rendering with cement/lime/sand mixed with a waterproofer before the oven is fully dried out.

If waterproofer in the render keeps the moisture out doesn't it equally keep the moisture in? Wouldn't this mean it is a bad idea to render now (and save myself the covering up process over the coming weeks) because it will make the drying out process longer or stop it altogether.

I am going to paint the finsihed oven to match the house so will gain water resistance this way but this does not help in the short term.

Any help for an almost dry oven in a very wet climate would be greatly appreciated. What to render with, what to add to the render and when to do it?

[texassourdough]

As a chemcal engineer by training I don't think that waterproofing will truly keep water in. I will probably impede the drying process but not stop it. It should be more effective at keeping liquid water out than at keeping vaporized water in.

I have dome oven and I have some water issues but not with the dome. My issues are with water that lands on the ledge around my oven and seeps through the sandstone I finished it with (bad choice) and under the oven. As a result I am planning to build a roof and walls around my dome. Good news is I will throw in some more insulation too.

I think the best water fighting approach is simply to encase the oven in a small "house" structure. That way "waterproofing" compounds are not an issue.

Hope that is useful!

[karl]

Serf.

When you fire your oven cold air is drawn in and heated. The temperature increase it's ability to hold water significantly. So yes, the waterproofing will stop water also from the inside (probably also in the form of vapor), but all your drying will take place as the water balance between the cold combustion air and the hot flue gas.

regards from karl

[Neil2]

Johnfisher.

Go ahead and put your "render" on then cure. (This sounds very like a stucco finish). No cement or lime base or even acrylic stucco is ever going to be 100% waterproof - at best it will be water resistant. In addition, minor cracks are almost inevitable.

Just cover with a tarp during heavy rain.

[david s]

jonfisher,
I agree entirely with your assessment re locking the water in. Cure before you render, then cover the render for a week to keep it damp to make it stronger. Then wait for at least 10 firings before waterproofing.It is worth taking your time to avoid cracking.

[Johnny the oven man]

^^^^^^ What he said. How can you push steam out through a waterproof barrier????

[Neil2]

I have a vent at the top of my oven that communicates with the insulation layer.

[Aaron18]

I have been checking out elastomeric paints as a sealer over a stucco-like final finish. This paint stretches up to 50% and stays flexible. One company that really repied fully to my email was Velspar. They say their elastomeric paint will be allright up to a surface temp of 200F. So if you cna put your hand on the outside surface of you fully heated oven and hold it there for 10 seconds you should be fine. If not, it will scorch and fail. One use of this type of paint is to seal stucco finishes that tend to carck againt moisture. So, lots of insulation.

[johnfisher]

Brilliant advice as ever. Am stirring the render now.
Thanks