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Community and Q&A

Moisture concerns — Vinyl siding over the top of stucco in Portland, Oregon

Cyrus Collins | Posted in Energy Efficiency and Durability on

I am looking at buying a 1907 duplex in Portland, OR, but have some concerns about the existing wall assembly.

The current owner had vinyl siding installed over the original stucco about 10 or 12 years ago. I’m not wild about stucco to begin with in this climate (Marine), and the fact that the stucco has now been compromised with fasteners for the vinyl siding makes me more concerned. There are no signs of moisture or structural issues that can be seen, but since we do not own the house we can’t do the inspections that might really show what’s underneath.

We will be doing some work to the house but don’t have a big budget, and want to have as good an idea of what we might expect ahead of time. We know that there is no insulation in the walls, and the home is currently heated with oil. Our short term plan is to update the heating systems (probably with high efficiency gas furnaces).

How concerned should we be about the wall assembly? Are there easy, non-intrusive methods that we could inspect the condition of the structure under the stucco?



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  1. GBA Editor
    Martin Holladay | | #1

    Stucco is a problematic cladding choice for a wood-framed building. To learn more about stucco problems, see To Install Stucco Right, Include an Air Gap.

    Q. "How concerned should we be about the wall assembly?"

    A. That's hard to say. I've definitely talked to building specialists who say, "I would never buy a house with stucco."

    That said, many homes with stucco have no problems. There are generally fewer problems with stucco in dry climates than humid climates.

    Q. "Are there easy, non-intrusive methods that we could inspect the condition of the structure under the stucco?"

    A. No.

  2. Cyrus Collins | | #2

    Thanks Martin,
    I read the article on stucco and it certainly reiterated my concerns. I was able to get into the house and do a little more investigating which led me to more questions. I was able to see a little bit of the sheathing around the panel, outlets, and a loose piece of interior window trim at the bottom of the window. Everything that I saw was in great shape.

    If the wall assembly doesn't have issues now (not that I was able to see everything) I wouldn't be too worried about it having problems in the future unless it is neglected. But for the past 100 years it has been heated with oil and has been able to dry from the inside in the winter which is when we get all of our moisture. Would it be a bad idea to switch to something like a mini-split?

    We would also consider replacing the vinyl siding with wood or hardy plank. If we did this than we would look into adding rigid foam to the exterior. Would it be OK to put house wrap and rigid over the top of the stucco? Would we need to strip the stucco off as well?


  3. GBA Editor
    Martin Holladay | | #3

    Installing a minisplit heat pump won't made the condition of the wall sheathing better or worse.

    If you ever decided to replace the existing siding, you would have the opportunity to investigate the sheathing. Areas of the stucco could be removed so that you could assess the condition of the sheathing; a good place to start would be under the lower corners of windows.

    If everything looks good at that time, I see no reason why you couldn't install a layer of exterior rigid foam over the stucco.

  4. Cyrus Collins | | #4

    My concern with the heating system change was that the oil is a hot, drying heat that might be helping dry out the walls.

    would HomeWrap be the best house wrap to use over the stucco? it seems to have the highest perm rating.

    Thanks again!

  5. GBA Editor
    Martin Holladay | | #5

    Q. "Would HomeWrap be the best housewrap to use?"

    A. The quality of the installation details matters more than the brand you choose. Pay attention to proper lapping rules, and integrate your window flashing and door flashing carefully with your housewrap.

    For more information, see All About Water-Resistive Barriers.

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