Stucco News

Question and answers on Stucco and Plastering
-- March, 2012


What is causing the stains on my house ?

          
Stains on
                  stucco
                                     Iron oxide.

Also known as rust, in different forms.

The downspout here has been clogged up
apparently for a long time. Water running out
from the joint at the downspout and the elbow has deteriorated the stucco so bad that the lath
has rusted through.

There is a possibility that the gutters and downspouts are steel, which is the cause
of the rust, but they look like aluminum to me.                                                                                     


More stains on house
These stains were apparenty caused by water
running over the gutter because the downspout
was stopped up.

The stains are probably caused by crud from
leaves, etc.

This also can be caused by iron oxide.

More stucco staining
   This is probably caused by dirt and crud from
the gutter, but there is another cause of stains that
look like this, namely iron oxide from the sand.
       We used a sand blasting sand from New Jersey
that developed spots in the finish coat within a month, especially where the wall got the most
rain. This was obviously from when the sand was crushed or quarried, small particles of steel from the machinery got mixed in the sand, and later became
rust stains.
   The stains didn't look bad on an orange stucco house we did, but looked terrible on the green wall we did.
    We ended up re-coating the green wall.
Iron oxide was also a problem for Finestone and
aggregated finishes years ago.
I thought this is important to bring up as a warning.