Building Management Hawaii December/January 2014 - (Page 22)
Cementious Coating Vs.
Polyurethane Foam
How best to repair below-grade waterproofing
By Sean Dunham
Waterproofing
B
elow-grade waterproofing is the
system that keeps or fails to stop
basements, elevator pits and below
ground parking from flooding.
Without below-grade waterproofing
these spaces would be uninhabitable
and accelerate the damage to structural
concrete and reinforcing. Below-grade
waterproofing has to stop a combination
of hydrostatic pressure and capillary
action. Hydrostatic pressure usually
comes from two sources-ground
water during heavy rain periods and
tidal action in areas below sea level (a
common issue in Waikiki). Capillary
action is cement's propensity for
absorbing water like a sponge.
Below-grade waterproofing falls
into two categories-negative side
and positive side. If you imagine you
are in a tunnel below ground, the
wall you can touch is the negative
side. The wall outside buried in
the dirt is the positive side. As you
can imagine, fixing or reapplying
positive side waterproofing in old
buildings is incredibly expensive
as you would be required to trench
out the dirt to expose the surface.
There are also areas that are next to
impossible to gain access, including
the horizontal slab, walls abutting up
to neighboring buildings and pits.
The costs to gain access to the
outside of the leak is often much more
expensive than the actual cost of the
waterproofing. That's when it's time
to use systems that can be applied
from the interior (the negative side).
ultra-dense surface that does not
allow water in its liquid state to pass
through but water vapor can still
pass through. Since the water vapor
can still pass, it doesn't condensate
between the cementious coating and
the substrate. This condensation is
what causes delamination and blisters
in conventional coatings when applied
as negative side waterproofing. The
downside to cementious coatings is
Repair
Approximate cost
Effectiveness
Cementious Coating
$12 a Square Foot
2
Polyurethane Crack Repair
$125 a Lineal Foot
3
Polyurethane Curtain Wall
$30-40 a Square Foot
1
The two most common and successful
products are cementious coating and
polyurethane foam grouts.
Cementious Coatings
Cementious coatings come in a
few different formulations, but the
concept behind them is to create an
their inability to handle movement.
So if your building is experiencing
settlement issues, it is not the right
fix. Also for horizontal applications, if
people or vehicles transverse the area,
you need to add a concrete topping
over the cementious coating since it
doesn't have good wearing properties.
Polyurethane Foam
The other common fix for belowgrade areas is expanding polyurethane
foam grout. It can be used in one of two
22
December 2013 - January 2014
BMH
www.buildingmanagementhawaii.com
http://www.buildingmanagementhawaii.com
Table of Contents for the Digital Edition of Building Management Hawaii December/January 2014
Signs & Safety How Do I Get Out Of Here?
Signs Of A Safe Building
A Sign From The Feds
Water Savings Coming Clean With Recycled Water
Water & Energy: Two-For-One Savings
Solar Hawaii’s Leaders In Solar
Waterproofing Cementious Coating Vs. Polyurethane Foam
Sky Arches
The $1 Million Mistake
Seal The Deal
Resin Injections Save Basement
Waste Management Keeping The Trash Industry Clean
Special Offer
Assistance Animals Making Room For Rover
Green Cleaning Be Green: Resources & Tips
Building Management Hawaii December/January 2014
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