ASHRAE Journal - July 2022 - 39

COLUMN BUILDING SCIENCES
PHOTO 1 Detached Garages. Playing with a row
of detached garages with stucco over block
construction.
PHOTO 2 Spray Rack. Adding water to the
stucco surfaces at the ASTM E1105 5 gph/ft2
(204 L/h·m2) rate. No induced air pressure, just
gravity, surface tension and capillarity and time.
) rate. No induced air pressure-just
face tension, capillarity and time.
PHOTO 3 Endoscopy for Walls. Knocked a bunch of
holes on the inside of the block walls and looked
inside.
PHOTO 4 Water Leakage. The suckers leaked after
a couple of minutes-right into the block cavities.
Not a couple of hours. A couple of minutes. Ten to
15 minutes.
PHOTO 5 Pushing Things. Being who I am, I
wanted to push things to serious failure. I kept
adding water. Long garden hose. Took a little over
an hour. It's why they call me a " hoser. " Neat
pattern.
the inside.† What I am now going to share with you will
be a surprise to some-and not a surprise to many.
Stucco renderings on block walls leak. Yup. When it
rains on a stuccoed block wall, it leaks. Always has. I had
a lot of fun with this 20 years ago in Orlando. I talked a
big-time production home builder into letting me play
with some of his houses before he sold them and normal
people moved in. Actually, it was as a result of the
three hurricanes that hit Orlando in six weeks in 2004
(Charley, Frances and Jeanne). Wow.
The deal was I could play with a row of detached
garages that were stucco over block construction (Photo 1).
I added a bunch of water with a spray rack (Photo 2). No
air pressure difference was induced-just gravity, surface
tension, capillarity and time. Knocked a bunch of holes
on the inside of the block walls and looked (Photo 3).
Think " endoscopy " for walls-building science proctology.
The suckers leaked after a couple of minutes-right
into the block cavities (Photo 4). Not a couple of hours.
A couple of minutes. Ten to 15 minutes. Yes, even I was
surprised. The old wizards I asked about this afterward
were not surprised-they laughed and said welcome to
the old folks club. Being who I am, I
wanted to push things to serious failure.
I kept adding water. Took a little
over an hour (Photo 5).
Everyone, relax a bit. The amount
of water added was a lot-the ASTM
E1105 5 gph/ft2 (204 L/h·m2) rate.
To put this into perspective, this
is 8 in. (203 mm) of rainwater per
hour-on a vertical surface. The
greatest amount of rainfall recorded
on a horizontal surface in the United
States over a one-hour period is 12
in. (305 mm) in Holt, Missouri, in 1947. If this amount
of water (the ASTM E1105 water rate, 8 in. [203 mm] per
hour) were ever to fall on a vertical surface in the real
world like a stucco wall, I'd expect a 600 year old man
walking animals two by two to a big wooden boat.
So what was the point of the water test if a nontypical
amount of water is put on the wall? Note there was
no air pressure difference. Wind changes things. They
do have " big wind events " in Florida and the Gulf Coast
and up to the Carolinas' coastline when it is raining.
Understanding that there are pathways was the key
point. It was always about fi guring out the pathways.
Here is the takeaway. Walls get wet. Mass walls with
stucco on them get wet. Always have. And, I am not going
out on a limb when I say they always will. The question
is how wet do they get and how do they dry? And can
we control it? Here comes the big news. They tend to
dry in both directions. And the drying can be managed
depending on the material choices.
Check out Figure 1. Rainwater enters the stucco.
Rainwater is absorbed by the stucco. Rainwater also gets
J U LY 2 0 2 2 ashrae.o rg ASHRAE JOURNAL
39
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ASHRAE Journal - July 2022

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