Damage To Wallboard Used For Exterior Sheathing Under Stucco

sequoia_2007January 18, 2009

We live in a townhouse complex and have an exterior wall that is made up from 2x4Âs covered with 5/8" thick Type SCX wallboard, covered with building paper which is covered by the exterior stucco. A few yeas back our HOA replaced the shake roofs with tile roofs. In the reproofing process the roofers cut back the stucco to install flashing along the edge of the adjoining roof.

While investigating for a termite infestation in the attic recently we noticed that the roofers severely damaged the sheetrock under the stucco when they installed the flashing for the tile roofs. This damage was seen in every stud bay in the attic and most likely the same damage is present along the wallboard in our master bath below.

I have a few questions:

How common is it to use Type SCX wallboard as sheathing?

Is the wall compromised with respect to moisture infiltration?

How should this type of damage be repaired?

Thank you for taking the time to read my post and consider my questions.


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I've never seen any wallboard type used as an exterior sheathing with the exception of firewalls in the seventies out here. They failed miserably due to moisture getting past/behind the single ply underlayment,(saturated felt). When using only a single ply underlayment, the scratch coat has a tendency to adhere to the underlayment causing moisture to condense behind and rotting the sheathing as well as mold concerns. With a double ply underlayment typically used these days, that risk is lessened as the moisture is trapped between the ply's and runs down and out through a drainage plane.

I cant say to repairing from the inside versus removing stucco/brown/scratch coats from the exterior and i question the flashing method used if it allows for drainage without penetrating the underlayment/wallboard. Typically that flashing would be furred out with a 1x4, which looks like that was done, but a perforated "j" channel would be installed in the area where the stucco meets the flashing in order for the moisture/wet to have an avenue of escape.

    Bookmark   January 18, 2009 at 8:13PM
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I was stunned when I realized there was only wallboard and paper under the exterior stucco.

I did a search the other day and found this thread.

Sheetrock as Exterior Wall Sheathing!!??

Maybe this type of construction was permitted in the past for attached townhouses. These buildings were built around 1984.

I am very concerned that the disruption of the building paper and wallboard by the roofers will allow moisture to enter our exterior walls and promote mold and rot. I found out from a homeowner who has been in the complex since it was built that the stucco was applied with one heavy coat instead of the traditional scratch, brown and finish coats. Apparently the builder was cutting corners at every opportunity.

    Bookmark   January 19, 2009 at 3:24PM
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The fact you have termites is an answer in itself. Termites like moist conditions.

I have only heard of other instances of drywall (doesn't even look like the moisture resistant stuff) on the outside through this forum.

Personally, I would sell the place as quickly as possible. As you've guessed, severe structural issues will be on the way and sooner or later I imagine the complex will have to be reclad which will mean a huge levy on the stratholders.

I guess this is where a big ethical question comes up - I don't know what your legal responsibilities are now, but once you inform the strata council (and they ought to know) it goes on the record, and nobody in their right minds will buy it (who knows, maybe that technique is common)

Presumably you already have to disclose the termite situation to any buyer.

    Bookmark   January 19, 2009 at 3:37PM
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"Type SCX" is one of the many material designations used by Underwriters Laboratories in its Fire Resistance Directory to identify proprietary gypsum panels with specific formulations. This one means that the panels are made by US Gypsum and are 5/8" Sheetrock Firecode Core Gypsum Panels.

These wall panels are intended only for interior use or at exterior soffits and have tapered edges for easier finishing. US Gypsum makes an exterior sheathing board with a moisture-resistant gypsum core encased in moisture-resistant paper on both sides and square edges. Only a fool or a con man would put it behind stucco with only one layer of asphalt saturated felt for a weather-resistant barrier. Are you by any chance in the desert?

I couldn't say much that would be helpful about the flashing without seeing a detail of how it was installed; the photos don't show enough. How thick is the stucco? How do the elements overlap?

    Bookmark   January 19, 2009 at 11:15PM
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In California you have to disclose these conditions, but we have no intention of selling. We planted our flag here 20 years ago and like where we live.

In the attic we have drywood termites and I have repaired all the damage I have found so far over the last two years. We also painted all the exposed interior wood in the attic with borates to deter future infestations. Our county is termite central and unfortunately our townhouse complex does not tent. Homeowners are responsible for wood destroying pests, not the HOA.

    Bookmark   January 20, 2009 at 1:52AM
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We are located on the Pacific Coast about ½ mile from the shoreline. In one of the photos above it appears the roofers added some type of paper above the flashing they installed. The paper that was originally installed on the exterior side of the wallboard was black in color. Regarding the thickness of the stucco, I believe it is thick, but only one coast as I described above.

    Bookmark   January 20, 2009 at 1:56AM
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Well I wish you the best, you must really like the place. Unfortunately I can only see expense ahead of you when things start to fall down, not to mention mould mitigation etc. I hope it doesn't cost you too much.

    Bookmark   January 20, 2009 at 3:38AM
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It doesn't seem like it would be too difficult to cut the wall back and do the flashing right. Get a proposal from a good waterproofing specialist (not a roofer) and make him draw the proposed detail or get an architect to do it. My fear would be paying for the repair and not getting the proper results. If I knew all of the existing conditions I could give you a couple of details to show a contractor but one missed piece of information could render the detail inappropriate.

Keep in mind that the "base flashing" should be flexible and self-adhering (Ice & Water Shield, etc.) well integrated with the wall and roof underlayment, and the "counter flashing" should be bent sheetmetal pieces that are stepped with the roofing tiles and compatible with cement stucco (not bare aluminum or galvnized steel).

The larger problem is the one layer of underlayment behind the stucco but the back of the drywall looks pretty good so maybe the amount of rain in your area will allow you to get away with untreated drywall used as sheathing. It would be wise to check on it on a regular basis.

    Bookmark   January 20, 2009 at 9:17AM
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Thanks for the well wishes. Our property suffered extensive damage due to water infiltration from properties up slope from us. I located the problem and our HOA was persuaded to replace the rear subdrain for our part of the complex. Check out what was left of the triple 2x6 girder that supported the center of our home and the second floor. Amazing what powder post beetles and mold can do to structural lumber.

We repaired all the structural damage and upgraded the foundation and support beams with the assistance of a structural engineer. After fixing everything and getting the place just the way we want it there is no way we are moving.

    Bookmark   January 23, 2009 at 4:02PM
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Thank you for trying to help. Since our HOA hired the roofers who damaged the sheetrock sheathing I think it is best they take on the responsibility for repairing it. I would imagine they are also responsible for any water damaged caused by the disruption of the drainage plane in the wall.

BTW, Sorry I am late getting back. Looks like the Garden Web is not notifying me when someone responds to my post.

    Bookmark   January 23, 2009 at 4:05PM
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In the face of all these issues, I can't imagine how I could possibly stay in a money pit, in view of the health and other risks the place seems to carry. You must really like it, and I can understand that, but it will only get worse. Beautiful kitchens/bathrooms etc are all fine and well but they need a structure to hold them up. When more issues inevitably arise (not to say all that these things don't happen elsewhere) you will be back on the treadmill. Mould is a biggie btw, it's incredibly bad for you.

I do understand this isn't a great time to sell, though.

    Bookmark   January 24, 2009 at 8:12PM
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The only issues we have now are the ones all homeowners have to address. We solved the mold issue by eliminating the moisture problem under the house and replacing all the insulation and sheetrock in the crawlspace. It was a lot of work, but we saved a lot by doing most of the work ourselves. All structural issues were addressed by replacing damaged members and upgrading the foundation and framing.

Looking forward to hiking in the Sierras again and seeing water where it belongs instead of under our home.

    Bookmark   January 25, 2009 at 12:55PM
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