Facility managers need to get to the root of the problem
when examining possible failures.
By Mark K. Howell
The issues that facility managers face today are increasingly
complex-especially when something goes wrong. While there
is no substitute for getting an outside professional involved
in the diagnosis and repair of a structural problem-be it
leaks, deterioration, or other scenarios that pose a potential
threat to the safety of the occupants-an understanding of
the building envelope will pay dividends in determining
the optimal solution.
A key ingredient to this approach is a thorough review
of the essential components that comprise a building, including
wall systems, roofing, and below-grade waterproofing. By
examining the way a building was designed and constructed,
as well as the repairs that have been made during its lifetime,
facility managers can help pinpoint the sources of many
problems.
Do Wall Systems Hold Up?
An
important element when determining the source of a problem
is the wall system. For it to function as intended, several
factors must be taken into consideration, including the
selection and design of compatible materials and systems,
proper detailing of material junctions and terminations,
installation and inspection of these details during construction,
the ability of composite envelope systems to function during
weather cycles, and proper maintenance by facility managers.
Even the slightest difference between the way a wall system
was designed and how it was actually constructed can have
a major impact on performance.
Unfortunately, the amount of detail shown on drawings does
not always provide sufficient instructions regarding intersections,
terminations, and penetrations of wall systems, resulting
in field personnel having to make educated guesses. This
scenario is especially true in the construction of cavity
walls, where there is zero tolerance for error in the design
and construction of wall systems. In most circumstances,
any design or field detailing error will result in water
infiltration or even more serious failures resulting from
infiltration.
A
wall system's design can be categorized into two main distinctions:
barrier walls or water managed walls. Barrier walls use
a blocking or interrupting mechanism to prevent the movement
of water to the interior of the building. Mass barrier walls
rely on sufficient thickness to prevent infiltration; face
sealed barrier walls depend on the exposed exterior wall
surface. With face sealed barrier walls, all joints and
interfaces must be sealed to provide this exterior barrier.
Whereas barrier walls are designed to keep out water entirely,
water managed walls allow for the control and discharge
of anticipated amounts of water. Drainage walls include
a cavity incorporated into the wall system that catches
water and flushes it to the exterior. When constructing
drainage walls, special care must be taken to avoid bridging
the interior and exterior wall.
Maintenance: Key To Proper Performance
Proactive
maintenance should encompass four main components: annual
maintenance budget, regular building condition assessments,
annual proactive maintenance, and seasonal visual inspections.
Integrating maintenance funding into the yearly budget is
essential for those committed to a property over the long-term,
and a regular review of the building's condition is a way
to assess the remaining life expectancy of the materials.
This is the only way for tasks such as sealant replacement,
window glazing, painting, coatings, and more to be integrated
into the budget.
Visual
seasonal inspections should include drains, gutters, and
downspouts. In areas of seasonal change, it is important
to perform these inspections after every major weather event.
In addition to planned maintenance repair work, capital
renewal funding should be set aside for existing structures
separately from new construction. When proactive maintenance
isn't enough, it's time for reactive measures.
Stopping Leaks
Certain processes should be followed when investigating
a leak. These seven steps (based on ASTM E2128, Standard
Guide for Evaluating Water Leakage of Building Walls) provide
a simple, yet consistent process.
Step
1: Review project documents. Locate drawings, specifications,
and other pertinent project information from the original
construction materials to determine the intended design
of the building. Change orders can be particularly helpful,
as they tend to highlight problem areas.
Step 2: Evaluate the design concept. Review the drawings
in order to understand the wall system application and how
the building was intended to manage water and/or moisture.
There are three main ways in which building systems can
become wet: when moisture enters from the interior, when
moisture enters from the exterior, and when the assembly
starts out wet as a result of using wet materials or building
under wet conditions.
In addition, this moisture can be removed from the exterior
or interior in three ways: liquid flow due to gravity (drainage),
air movement (ventilation), or vapor diffusion (vapor pressure
difference). All of these mechanisms can act independently
or in combination to dry out the substrate.
Step
3: Determine the building's service history. Review previous
repair attempts, work orders, or reports to uncover any
faulty repairs.
Step 4: Visually inspect the building. Start at the roof
and work from top to bottom to develop an informal visual
survey of the structure. Take pictures of the details: penetrations,
parapet walls, flashing, mechanical curbs, copings, roof
cants, and weep holes. Also, document the damage to the
interior of the space. Review discrepancies between the
visual survey and the original design.
Step 5: Perform investigative tests. Testing provides an
opportunity to recreate leakage and water paths under controlled
conditions. Non-destructive testing involves methods that
simulate either surface flow or wind driven rain.
Surface flow can be simulated by wetting a wall area with
a matrix of uniformly spaced spray nozzles that deposit
a full film of water though a soaker hose (a trickle of
water from an ordinary hose also is suitable). If surface
flow alone is not enough to determine the cause of the leak,
wind driven rain can be simulated using a pressurized chamber
that is sealed to the wall test area.
If
these testing methods prove ineffective, destructive testing
may be necessary. Although destructive testing allows for
the determination of the damproofing or flashing condition
(both of which are designed to divert the water to the exterior)
the amount of this testing should be limited, because the
process may expose mold and bring an entire additional element
to the investigation.
Step 6: Analyze the findings. Analyze the gathered information
and determine the effectiveness of the design concept and
any attempted repairs. Is there a life safety concern? Was
mold or mildew found? Can any further tests clarify the
analysis?
Step 7: Prepare a report. Present the information gathered
from the previous steps in a walk through format, including
photographs and solutions for fixing the leak.
Facility managers armed with this knowledge about their
facilities have the opportunity to implement long-term solutions
that will likely save money and time when compared to quick
fix solutions. Following these steps will enable managers
to create a more efficient, durable, and cost-effective
facility for everyone to enjoy for years to come.
Howell is employed by Structural Preservation Systems
(www.structural.net)
in Baltimore, MD. Questions about this article can be sent
to him at mhowell@structural.net.
Have you had any structural issues with your
building envelope? Share your stories by sending an e-mail
to schwartz@groupc.com.
