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Failing Facades

What's a Board to Do?

Article written by Jack Carr, P.E., R.S., LEED AP, Criterium Engineers
Published in Condo Media, June 2013

No matter what type of building you live in, the facade will begin to fail one day. Whether it is water infiltration, spalling concrete, crumbling brick, or cracking wood, it is only a matter of time. I do not want to turn your building committee into structural engineers or forensic investigators — after all, I have to consider job security — but there are some techniques or terminology you might want to be familiar with when it is your time to face a building exterior problem.

The Role of Water

The villain in most façade failure mysteries is typically water. It causes corrosion, erosion, internal leaking, paint peeling, rot, settlement, and a host of other building envelope woes. If your building has concrete elements suffering from spalling or cracking it might be due to the reinforcing steel in the concrete becoming heavily corroded due to water penetrating the surface. Ordinary rust scale expands with incredible force per square inch when confined — think bulldozer power.

Many absorptive façade materials (concrete, sandstone, mortar, fired-clay masonry) can be seriously damaged by cyclical freezing and thawing of water entering the material through natural porosity or surface hairline cracks. These pockets of moisture can be trapped in façade walls whose freezing can expand, causing further cracking, spalling, or displacing adjacent masonry by a phenomenon called ice lensing.

This spalling can create dramatic loss of structural integrity to parapet walls, retaining walls, and cantilevering decks, not to mention the safety hazards from falling façade components. Complicating the diagnosis problems and the repair solutions is that spalling concrete can be caused by forces other than water. Similar concrete failures can manifest themselves by compression, tension, or vibration overloading.

Material Matters

Equally important in a façade investigation is understanding what materials make up the façade, as looks can be deceiving. Most of the old brick buildings in major cities use the exterior brick to support the interior floor
framing and are thus called “bearing wall masonry.” These heavy walls were designed to prevent moisture from entering into the building’s interior spaces by the brick absorbing water in its multi-layers of brick and drying out when the weather improved. Over a hundred years ago, steel framing was introduced, allowing the building designer to hang the exterior façade skin on the perimeter of the frame to produce more lightweight and cost-effective buildings. Today’s brick building uses brick as a veneer in which the brick is only the first line of defense against water infiltration. The brick actually shields the true water barrier sheathing behind a cavity space. This cavity acts as a drainage channel with weep holes at the bottom of the brickwork.

Similarly, many older buildings are covered with a stucco façade surface, which is a cement parge coating over a steel lattice similar to plaster placed onto wood lathe strips. Modern buildings use an Exterior Insulation Finishing System (EIFS) seen on many condominium and retail building exteriors. An EIFS façade depends on interior drainage surfaces and is totally different in repair methods than stucco.

In addition to judging the cause of the façade problem, it is important to determine its seriousness and whether immediate repair steps are necessary. If it is not an “active” problem, it can be set aside in favor of other more pressing issues requiring capital outlays from the reserve fund.

To address these questions, there are a variety of invasive and non-invasive techniques to investigate the problem. If the concern is corroding imbedded steel, there are firms providing chloride ion content testing of concrete or mortar to gather quantitative evidence of corrosion potential. Simple stain gages can be placed over cracks to detect active movement. Infrared thermography can discover unseen façade connection failures, delaminations, or thermal “short circuits” due to wet insulation. There are a variety of water moisture content meters available at building supply stores and woodworker hobby shops that can accurately detect and measure moisture in a variety of materials including wood, drywall, and concrete.

So the good news is there is plenty an observant building committee or property manager can do to prevent small façade problems growing into something major.


 
© 2013 CRITERIUM ENGINEERS