Stains on masonry blocks.

[David C. Macy]

2000 built Colonial with a partial finished basement.

Vinyl siding no brick veneer.

Stains observed on only one wall adjacent a concrete porch slab.

Stains on top third of block. 20% moisture noted with a meter.

What do you think caused the stains?

No downspouts in vicinity.

[Jeffrey R. Jonas]

Did you check level of the slab? Sloped towards or away from the home?

[David C. Macy]

The porch looked great. No cracks, sloped away. And it faced east. Most weather around here comes from the west, north and south unless we get a Northeaster.

Just seemed a strange place for moisture and it was not the typical coloration of stain.

[Marcel R. Cyr]

David, I have seen familiar stains like that on block before.

Since I can't see the whole picture of conditions, I am only guessing.

Those appear to be stains created by wet plywood, OSB, regular lumber etc., leaching through the block work and creating that dirty rusty water stain. Water and/or moisture is negating the Building Envelope in that area somehow.

Hope this helps.