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An outside, completely isolated, balcony column structure

peter_mare | Posted in General Questions on

In an outside, completely isolated, balcony column structure that must be finished in stucco and built using steel studs, would it be possible for any moisture damage in the inside of it if we were able to completely seal the inside from the elements? In a 4c zone, applying stucco to acrylic panels to make a stand-alone column.

This is a renovation. The column is completely isolated from the dwelling. It must use a stucco finish (acrylic or not) (or something that looks like stucco). The idea of the acrylic or plexiglass panels is that they will never rot, they can structural, using steel studs (to help secure railings). The column is 10″ x 10″ x 7 feet. The stucco part is totally exposed to rain/wind.

Would we get any dew formation or mold in the inside of the air-tight column? What would you recommend the sheathing to be for it to never rot or rust, I suppose? 🙂

Using some kind of primer for galvanized structures and an anti-rust paint (tar, epoxy-tar,…) to prevent moisture/rust, mold, and sulfur dioxide damage. The studs would be dipped into the covering. The advantage would be –in effect– to attach an impermeable membrane to one of the most vulnerable part of a wall assembly. Your thoughts?

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  1. GBA Editor
    Martin Holladay | | #1

    I don't think it's possible to create an airtight box as you propose. Nor do I think that an airtight box is necessarily desirable.

    What you want to do is to choose durable materials that are unlikely to rot. Assemble the materials in such a way that that the assembly sheds water, but is able to dry readily. That means that vapor-permeable assemblies (cement backerboard or traditional Portland-cement-based stucco) are probably preferable to materials with acrylic additives that limit vapor permeance.

  2. peter_mare | | #2

    Thanks, Martin, for answering my questions! Much appreciated! I understand that the idea of using plastic boards is a bit strange, but plastic does not rot or rust, so it is an appealing sheathing solution. But, I agree with you, even if we were to seal the box completely and even though there would not be any build-up of moisture (since no one would be "living inside the column), there would be still some water vapour inside the box Of course, acrylic or plexiglass doesn't rot, but mould could grow in it! Not sure what damage mould does to acrylic panels, if any, but if we can avoid humidity, we should. So, I agree with you. What about the idea of having one or two small venting areas (6" x 6"), through the panels and through the stucco (SMALL plastic mesh sticking at the border of the coverings at the top and/or bottom of the structure (away from rain)) covered with an exterior vent (placed after the stucco has cured)? Now, about the stucco on the mesh screwed to the acrylic panels. What mesh should I use? I am not sure why there are so many types. I would not use any elastomeric paint on the stucco, BTW. Right? but a clear water-based, breathable sealer. Right?

  3. Expert Member

    Have you thought of using a vented base? The manufactured ones may not suit your need but you could make, or have made, a variant.

  4. peter_mare | | #4

    Thanks Malcom! Oh! Good idea! I will see if they can work!

    BTW, I am thinking of priming/painting or using resin galvanized steel studs (not sure how galv. steel studs likes resin) to delay to the maximum rust. I read that they have special primers and special anti-rust paint. Sulfur dioxide (acid rain) might be an issue, but not sure. If not, this should be good for a very long time. This will make the use of membranes useless or redundant. Time to coat the studs in a dip to dry method should be fast, but I hear that they need to cure if water-based painting is used. I doubt that the primers and paint would be water based. As an option, I have thought of using an epoxy-tar product, but I think a resin is more appealing as we are still discovering ancient insect in old sap which is is like a resin, I think. What do you think? I know this is not green, but if it does not need to go to the landfill, it is one way of doing it! :)

  5. peter_mare | | #5

    Of course, I am not sure how stucco applied to a lath will work when an acrylic or plexiglass panel is used. That should be an interesting experiment! Any thoughts? I read that stucco cures/dries from the inside out.

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