All opinions welcome

[Stewart Mussolum]

I know what it is but would like opinions on the cause. Note the warp in the vinyl siding above the stains.

[Jeffrey R. Jonas]

No pic to see.

[rbero]

h'mm if i could see it maybe it would be better.

[Stewart Mussolum]

Sorry look again.

[Bob Elliott]

Efflorescence is caused by salts in the brick coming out during water evaporation.
You have mortar missing in that area.

I would say there is a water intrusion issue.

Need to see the top and how was the roof above that area.
Did they have weeps and a moisture barrier at the lintels and other areas?

[David P. Valley]

Ice damming causing built-up moisture to infiltrate behind siding?

[Jeffrey R. Jonas]

Originally Posted by smussolum

Note the warp in the vinyl siding above the stains.

Improper installation of siding, fasteners too tight, causing the siding to buckle (expansion/contraction), allowing moisture to penetrate behind the siding. ???