By Jon Eakes
How soap can
rot your exterior walls
Soap is often used to
clean house siding, usually with a pressure washer. Soap is also often added
to stucco to make it more workable. Soap is good stuff - isn't it? If you
believe that, read on.
Let's start with taking a look at just what soap does that makes it work so
well both for cleaning surfaces and for making stucco flow better. Pure water
has a tendency to hug itself. That is why water drips off the end of a faucet
in individual droplets rather than just flowing as a tiny stream. The surface
tension of the water wants to keep it together in the smallest form possible,
so it tries to form a ball or sphere. The tear drop shape of a drip is simply
the elongation of the sphere before it lets go of the faucet. In fact if you
use a stop action camera to see that same drip in the air, it is an almost
perfect round sphere.
We see that with water on a newly waxed surface. Drips of water will actually
form balls sitting on top of the surface. When you add more water it can't
stand up high as a large ball so it flattens out, but the outer edge of a
puddle of water on a waxed surface will be curved, even rolling back under
like that ball. You can see that in the top picture. When you add the smallest
quantity of soap to that water, it instantly looses that surface tension and
flows out, as you see in the bottom picture.
Soapy water works for removing dirt because the soapy water has little surface
tension and can flow under - even through - materials that would not absorb
water without soap. This same "slippery" function is what allows
soap to make stucco work in a more fluid way.
So, to this point, soap is doing what we want it to do. The problem with soap
and houses is that the two photos show water on a house wrap. House wraps
are sheets of material designed to stop liquid water from penetrating but
they are porous enough to allow water vapour to pass through. They do this
by having a sort of waxy surface and are made of a woven material, or small
pin holes, that have openings too small to allow water that is being held
together by its own surface tension from getting through the holes. However,
water vapour, which has no surface tension, can get easily through. If you
add soap to that water, its surface tension is gone and now the water can
flow through the material as easily as it will flow through paper. When I
left those two sheets of house wrap sit for a while, the first one simply
dried up. The second one dripped most of the water through to the other side
before it dried up.
Waterproofing washes
away
The point is, soap on a building paper or house wrap removes its waterproofing
qualities. This is not a good thing. The first signs of this problem came
from houses which had stucco finishes and soap had been added during application.
It has also shown up with soap being deposited by pressure washers shooting
up into ventilation passages of siding. You might think that the soap would
eventually rinse off and the problem would go away. That would probably be
true if there was enough water flow to actually rinse off the soap but, more
likely, siding leaks will only provide enough water to wet the house wraps,
not rinse them.
Hence, allowing soap from any source to come into contact with building papers
and house wraps could eliminate one of the most important water control mechanisms
we put on our walls. Use proper stucco additives, not soap, to make stucco
more workable. Spray downhill or horizontally, not uphill, with power washers
when cleaning walls - and explain this to your customers so they won't accidentally
sabotage the protective systems you have built into their homes.
Problems in walls are not caused by the presence of some moisture, but by
having just a little too much for the given conditions. Non-waterproof building
paper could let in that little bit of moisture that becomes too much for a
particular wall.
HB
Montreal-based TV
broadcaster, author, home renovation and tool expert Jon Eakes provides a
tool feature in each edition of Home BUILDER.
www.JonEakes.com
