Need some construction advice...

[TwoFlowersLuggage]

This is a picture of a wood sliding window. The wood on the *inside* in one corner seems to be shredding & powdery. This window is in an area that gets a lot of sun, and this house is near the ocean, so it has been constantly exposed to ocean air. The outside of the window frame seems fine - it is only in this inside corner that we're seeing this. As far as I can tell, nothing is rubbing on this area - the window opens and closes fine with no rubbing.
And, it's not just on this window, it is also being seen on a couple of other windows. The house was built in 2007, so it is ~11-12 years old.

Edit: It is actually a hybrid vinyl-clad dual-pane window with wood sills and other wood bits - I don't know the proper terms for all the window components.

So: What causes this? Is the only way to stop this to replace the entire window? I'm not sure what brand these are - but they are probably a name brand like Milguard or Anderson.

[Tony_Wood]

Do you have water penetrating the seal?
The black seems to be mold from a moisture problem.

[Mumbleypeg]

I agree with Tony. We had a similar problem with the windows in our church fellowship hall which was built in the 70s. Over years of time, moisture penetration from both rain and condensation had created what looks very similar to your pictures. We had to use a bleach product to kill and remove the mold, had the window frames re-caulked, new weatherstripping, and had to replace the interior sills and other cosmetic repairs. The interior sills were "powdery" mainly in corners and to some degree along the interface with the windows. The longer you let it go the worse (and more expensive) it gets. The "powdery" situation was on window sills on the south and west side, none on the north. So I think in addition to moisture, sunlight was part of the issue.

Strangely the church sanctuary, built in 1914, has not exhibited the same problems. Those windows are also wood-framed but the glass is glazed and covered by permanent exterior storm windows designed to protect the stained glass, so they're not directly exposed to weather.

Ken

[peanut740]

Anderson windows should have a guarantee. They have an etch on the glass in a lower corner of the glass.

[mrwatch]

Anderson windows should have a guarantee. They have an etch on the glass in a lower corner of the glass.

more likely they will say it was the installation. unless a seal failed. mold will cause respiratory problems, need to kill and remove it.

[FRJ]

So: What causes this? Is the only way to stop this to replace the entire window?

It would be nice to have a picture of the exterior of the window showing siding and how siding is applied to the window on all sides.
Which would tell only part of the story.
With what you have shown, you have, in my opinion, is a flashing problem. Amateurish and non existing flashing allows water to enter a framed opening like this. I don't see this as a window problem.
An experienced carpenter who would be willing to look through the house could be most beneficial.