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Moisture?? - Forno Bravo Forum: The Wood-Fired Oven Community


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  • Moisture??

    We installed a Casa 2G 90 about a year ago in our back yard in North Vancouver (very very rainy). It was built as per the installation instructions by a local contractor and covered in waterproof (?) stucco. We cured it, and used all summer\fall with no issues. Now after a long rainy winter the performance of the oven has dramatically changed. Doesn't get as hot and cools down WAY faster. What's really odd is the firebrick on the floor is only heating to ~350 even after 3 hours of a pretty good fire. I'm wondering if the stucco is not completely waterproof and the insulation surrounding the dome has gotten wet and the floor has retained moisture as well. Not sure what to do at this point, any help\comments greatly appreciated!

  • #2


    • #3
      The symptoms sound like the CaSi insulation has gotten wet, whether it be from a leak in the stucco, water migrating from the granite or water coming in from the entrance, the only way to solve the problem is to cure the oven again. I will take several firings to get the moisture out of the insulation. Is there a weep hole in your hearth for water to drain out? If not you may want to drill a couple if you can access from the firewood storage area. The oven has no protection from the NW's rain so you might have to tarp it during the rainy times or build a cover over the oven. Some wet climate builders have build a second "storm" door for the front opening as well.
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      • #4
        I don't believe stucco can be made truly waterproof - and even if it is, there is still the problem Russell point out, which is water can come in around the bottom of the oven where your dome meets the hearth slab. I live in Seattle and face the same weather issues - I loved the look of an igloo but didn't think I could keep it dry so I went with the doghouse. Keep firing it and it should dry out, I would suggest a tarp to cover it when you're not using it.during the rainy season.
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        • #5
          Thanks Guys,
          Very useful. I've been in touch with Forno Bravo and they figure wet floor insulation as well, maybe from moisture coming down the flue when it's rainy and windy. I think a tarp or cover of some type will work once I get it dried out.


          • #6
            Another place for water entry is where the outer shell joins the flue pipe. A considerable amount can run down the pipe and into the insulation space here. The way the Casa is designed makes it difficult to seal at that point because it is fairly low and close to the fire making it pretty hot. Also driving rain entering through the oven mouth if it's facing the weather. An easy way to test if the dome insulation is wet is to place your hand on top of the dome.if it's hot then your insulation isn't working well, in normal operation it should only be cosy warm. At least that's how I tell with my ovens, which have a pretty thin outer shell. An acrylic elastomeric product painted over the render does a good job of waterproofing it and because it's so stretchy can cope with filling minor cracks in the render.
            Last edited by david s; 03-26-2017, 02:07 PM.
            Kindled with zeal and fired with passion.


            • #7
              For me, a roof is the way to go.

              It has been raining here for a couple of days and I have a deep craving for a couple of my wood-fired pizzas.

              Rain has mostly stopped but if I didn't have a roof I couldn't start cooking in case it started up again.

              I've got a cover as well in case a strong wind blows the rain in from the side. I find after a couple of days of rain my oven's performance will be affected even with these measures. The tarp maybe traps the humidity inside the oven.

              Edit: re. "I find after a couple of days of rain my oven's performance will be affected even with these measures." - Actually this time it worked perfectly. Maybe the wood was damp before.
              Last edited by AndrewT; 03-27-2017, 01:25 AM.


              • #8
                Just had another thought because you said "very very rainy" you may have an issue with water wicking up from the stand into the underfloor insulation. Probably not possible for you now, but I always try to seal between the stand and the supporting slab to prevent this. I also add an additive (Xypex) which apart from enhancing the concrete strength makes the concrete waterproof. If you find drying the oven after your wet season to arduous you may have to consider a roof over the oven as others have suggested.
                Kindled with zeal and fired with passion.


                • #9
                  We currently have a large Cat 4 cyclone (Katrina hit the Louisiana coast as a Cat3) bearing down on us with it expected to cross the coast in a few hours. Fortunately the eye is some 200 km to our south so we don't expect too much damage. Those in its direct path though have just recorded 195 mm (over 7.5 ") in one hour. That's enough to make any oven wet no matter how well it's sealed. One of my ovens went through cyclone Yasi (Cat 3) several years ago and the tidal surge had it completely under water as the house was on the beach. After drying out it performed as good as ever. The flue hadn't even been dislodged.
                  Last edited by david s; 03-27-2017, 04:54 PM.
                  Kindled with zeal and fired with passion.