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Any thoughts on why a stain is leaching though my sheetrock and paint?

last month
last modified: last month

Over the past 10 years, a brown stain has been slowly showing up and darkening on a sheetrocked vertical support beam. As you can see from the photos, the staining has been blocked by possibly a metal corner sheetrock bracket with the staining leaching through the holes. I first suspected possible black mold, but I cut a plug out if the sheetrock down to the wood beam and saw no sign of mold. But what I did find is that the vertical support beam has some sort of shiny metallic coating which does scrape off. I now susoect over the years this coating has been somehow interacting with the sheetrock and causing the discoloration. I have tested the silver coating for lead and it is negative. Has anyone here seen such a metallic coating on wood beams? The house was constructed in the mid-50s. For now, my plan will be to repaint and simply use a few coats of stain blocker as primer, but am open to suggestions as to what is going on here.. Thanks. —Bill




Comments (18)

  • last month
    1. That's wild. I agree your solution is best. The cause is a real who-done-it.
  • PRO
    last month

    Moisture issue.

  • last month

    I was considering that because the vertical beam is on an outside wall, but the board is perfectly dry and I am also beginning to get the same type of stain on a vertical support on the opposite side of the room (an internal support).

  • 29 days ago

    Is there a heating pipe in there for the baseboard heat? Maybe that's helping accelerate the reaction. That looks like the plaster in our 50s house.

  • 29 days ago

    Get a moisture reader to check levels there

  • 29 days ago

    It looks very much like the type of plaster that was in my 1951 house, so are you sure its even sheetrock? Cud be something from the plaster itself.

  • 29 days ago
    last modified: 29 days ago

    The sheetrock plaster is bone dry and there are no baseboard piping runs or risers within that sheetrocked support. In addition, the same staining has been slowly showing up over the past 8 or so years on a similar internal sheetrocked vertical support on the other (internal) support wall. (See photo.) I’m beginning to think the silver coating on the wood may be old adhesive that originally held the sheetrock to the support and has been chemically leaching through it over time — though I have never heard of a metalic-looking glue.


  • 29 days ago

    It seems to be sheetrock. This room was once two bedrooms and a wall was taken down to make a large den sometime before we bought the house in 1989. The living room walls are plaster over lattice. This stained wall is plaster sandwiched between two cardboard layers — so I assume old dry sheetrock.

  • 29 days ago

    That silvery coating could be aluminum coloured rust-proof paint, it was a popular choice in the 70's and 80's. I don't know why someone would paint a beam that is about to be covered with sheetrock, but perhaps they re-used lumber from another project that was already painted.

  • 29 days ago

    Previous owners might have asked advice on Houzz where they were told to coat beams with metallic paint before finishing walls.

  • 29 days ago

    That’s interesting regarding the aluminum colored paint. Maybe it was a new type of fire-resistant paint for treating the wood frame when the house was being built? But then again, i dont see any such coating on the floor joists when I an in the basement. I’ll try Googling silver/aluminum paint. Thanks for the suggestion.

  • PRO
    29 days ago

    Brown often indicates rust which indicates moisture from somewhere.

  • 29 days ago
    last modified: 29 days ago

    I do have some occassional water infiltration through the concrete block foundation on that side of the house. Maybe that wood has absorbed some moisture from the humid basement air below it? The stain started at floor level and progressed upward over the years. But the support is not in direct contact with the foundation and does not run all the way down to the basement, though it may be resting upon an iron I-beam that spans the basement and supports the house. Hard to see. But the I-beam is definately not wet and doesnt explain the internal vertical support wall on the other side of the room where the sheetrock is also showing the beginning signs of discoloring. Would be interesting to see if that wood support beam behind that sheetrock also has a metallic coating. But why the staining has traveled up from the floor on the two opposite support walls is a mystery, considering the rest of the walls in that room (even the outside wall) has developed no staining at all. And if it was due to the metallic coating, the entire length of that piece of sheetrock would be stained uniformally. If it is caused by moisture below, it has taken a very long time to develop, but it seems the most logical answer at this point.

  • 28 days ago

    Definitely moisture.

  • 28 days ago

    Does it smell? I would get a moisture meter and test it.

  • PRO
    28 days ago

    Capillary action can wick moisture a LONG way. It gets water to the top of the redwoods, after all.

    https://www.usgs.gov/water-science-school/science/capillary-action-and-water

  • 28 days ago

    Hi, Looks like a moister stain. cool on one side and warm on the other side. Doesn't look damaged. What I have done with water stains, when dry is get a can of spray shellack and apply it to the stain. when dry, about 30 minutes then paint.

    Good Luck Woodbutcher

  • 28 days ago
    last modified: 28 days ago

    The staining doesn’t smell, even with my nose to it. And I dont think I will be able to find the source of dampness, especially if it is due to capillary action in the wood. The outside wall was insulated and vinyl sided a few years ago and is water tight. I will simply apply a couple of coats of sealer and then paint. Should last another 20 years. Thanks for all of the brainstorming and suggestions you all have peovided me.