Building Envelopes: The Outside Story

Comprehensive inspection and maintenance of key components keeps out water and protects assets and operations

By Mark E. Leeman  

Facilities present maintenance and engineering managers with an array of evolving challenges and priorities. One constant, if overlooked, priority is proper maintenance of the building envelope. But this area of maintenance often presents more questions for managers than the initial problem suggests. In some cases, the answers to these questions can be disheartening, such as when workers must quickly perform large, burdensome projects.

A comprehensive building envelope maintenance program can deliver a range of important benefits to organizations. It can prevent building deterioration, reduce long-term maintenance costs, improve a building’s appearance, and reduce occupant disruptions caused by such problems as leaks.

Perhaps just as important these days, proper inspection maintenance of a building exterior can help workers identify and repair sources of energy waste caused by poorly installed or maintained exterior materials and components.

Inspection Issues

Maintaining building exteriors is essential for protecting the efficient operation and appealing appearance of a building. The envelope blocks the entry of water and wind, helping to prevent interior damage and disruptions and to maintain a comfortable environment.

If managers do not address these components as needed, the resulting failures and deterioration can prove costly in the long run. Exposure-related problems include damage from water infiltration, mold growth and loose elements falling from the exterior. A proactive approach to exterior maintenance can prevent these occurrences, reduce liability and keep tenants happy.

A maintenance program for building exteriors should include regular assessment and observation. Managers can implement the program using in-house workers who perform the inspections biannually. Specifically, inspectors should note areas of shifted or displaced elements, cracks, spalls, stains, or other forms of deterioration they can observe from the ground, roof, balconies, or terraces. Window cleaning crews can aid in inspections. Since they have access to upper stories of a building that maintenance staff probably can’t observe, ask them to report any exterior components or materials that might require attention.

Observations do not need to be confined to the exterior of the building. Inspectors also should record reports of water entry into a building, including when the entry occurred, its extent, and weather conditions at the time.

Repair Strategies

All building envelopes eventually require repairs, regardless of whether or not a maintenance program exists. The key is detecting problems early before more serious issues occur.

Generally, significant repairs to building components do not occur unless something is wrong, but all elements require refurbishment over time. Examples of common repairs include tuckpointing cracked masonry joints, replacing deteriorated or aged flexible sealants, and cleaning soiled stone or concrete.

Performing repairs on deteriorated or aged building components can prevent future deterioration of adjacent exterior elements or water entry, reducing the possibility of long-term increased maintenance and repair costs over time. For instance, a crack in an outside element left unrepaired can widen or lengthen with freeze-thaw cycles and allow water entry, which could corrode structural steel elements behind the facade.

While most exterior projects involve surface repairs, some projects involve repairs to waterproofing within an exterior wall cavity or a structural attachment of the wall itself. Structural repairs can be expensive and disruptive, particularly if managers have concerns about fall hazards. But the risk involved with building components becoming loose and falling warrants immediate correction of the problem areas.

Corrections to reattach exterior elements can be complicated, and managers need to find creative solutions. Methods suitable for new construction often are not applicable for repairs. Rebuilding walls with new brick or stone presents a challenge in matching new materials to the existing appearance.

Repairs related to the drainage of wall cavities can be just as disruptive as structural repairs. Water infiltration often is related to problems with through-wall flashings and wall drainage. Typical problems include sealed or inadequate weeps, mortar-filled cavities, lack of proper terminations, and misplaced membrane.

Sealing off weeps often occurs when workers do not realize the purpose of these holes, which is to allow water to drain from the wall. If water infiltration is minimal, workers usually can perform repairs at the immediate area to address the leak.

Managers should pursue large-scale work involving through-wall flashing only if few options remain. Workers might need to remove masonry to install or replace through-wall flashings might need to occur outside of normal business hours if the work involves sensitive tenants.

Coatings and Sealers

Managers can specify the use of coatings or penetrating sealers to prevent water infiltration at the façade. Each has advantages and disadvantages, depending on the intended use.

Both products can reduce water infiltration and help to more readily shed precipitation from surfaces, which in turn can slow the accumulation of dirt and staining on building components and reduce salt leaching. A coating usually can bridge small cracks, while a sealer does not. This bridging reduces water penetration into balconies or terraces, for example, and prevents moisture from reaching reinforcing steel.

Before applying either product, workers should apply a small amount to an inconspicuous surface area to determine if the resulting appearance is acceptable or not.

As with any preventive maintenance material, coatings and sealers require post-installation maintenance to ensure effectiveness. The service life of most coatings is 10-15 years. Some initially require multiple layers but only need recoating once to extend the service life.

A penetrating sealer costs less than a coating and generally requires one application, but its service life is 5-10 years. Workers must apply both products routinely according to their service lives to provide long-term benefits.

Applying a coating or sealer is especially helpful if stained or etched window glass becomes a large problem. Glass etching occurs when rainwater absorbs chemicals from concrete or masonry and carries away lime and other elements that can scratch window glass.

Cleaning Considerations

Managers also can improve a building envelope’s appearance by specifying certain cleaning methods. When selecting a cleaning procedure, managers should use the least aggressive method for the situation.

Power washing with clean water is used to clean normally stained surfaces. The process removes general airborne dirt and smog, but rust or chemical stains and heavy efflorescence might require even more aggressive removal methods. It is best to clean these areas as soon as possible so stains do not become permanent.

Chemicals and other cleaning solutions sometimes can clean heavily soiled areas. Again, workers should apply the material to a test area to view the resulting appearance.

No single approach to cleaning frequency applies to all buildings. Because cleaning primarily addresses a building’s appearance, the frequency depends largely on the desired appearance.

In practice, different surfaces show dirt more easily than others and, therefore, require more frequent cleaning. An exterior cleaning cycle of 5-10 years is reasonable for many buildings. From a functional perspective, managers should make the decision of when to clean based on the nature of the staining.

A large portion of the expense related to most exterior restoration or repair projects involves erecting swing stages to perform the work. Workers might need to move and reset stages many times during a project, which is costly, time-consuming, and disruptive.

As a result, bundling repairs to address immediate and near-future needs into one project is recommended, which is an efficient use of project funds for swing stage work.

This is another reason an exterior maintenance program can help. Managers know the condition of various components can schedule multiple replacement or repair projects at the same time, rather than react to one severe problem at a time.

If properly maintained, a building’s exterior will function as intended for years to come. But if it is neglected, the resulting deterioration and problems might prove costly and insurmountable for regular maintenance. Correcting defects of an exterior wall that leaks air or water also can increase the energy-efficiency of a building, helping to reduce utility bills. Performing assessments and necessary repairs regularly, no matter how seemingly insignificant, can help prevent larger and more costly repairs in the future.

Matthew P. Kutzler, E.I.T., is a project engineer at Facility Engineering Associates P.C. in Fairfax, Va. He has conducted many exterior wall system evaluations and designed corrective repairs. Mark E. Leeman, P.E., is an associate with the firm and has conducted assessments of many types of exterior wall systems.

Inside Issues: Technology and Strategies

When problems occur in a building’s exterior wall system, they often are difficult to see because the cause is high above the ground or behind cladding. So inspectors use various approaches to determine the causes of exterior wall failures.

But making exploratory openings in a wall system is slow, disruptive and expensive, so they use alternative methods to gather information. Among the most common methods are these:

MAGNETIC COVERMETER. These devices non-destructively measure the depth of reinforcing steel in concrete, and engineers use them to identify ties in masonry wall systems. A covermeter survey can determine if brick ties have been placed properly in the wall system without making openings in the wall.

SPRAY TESTS. These tests are used routinely to isolate the location of water entry in a wall system. Inspectors usually conduct tests by applying pressurized water to a wall or window system and monitoring the interior for water entry. Typically, spray tests are conducted from low to high on the area of the wall in question. Isolating the location of water entry can reduce the number of expensive openings investigators make in a wall before determining repairs.

BORESCOPE. Engineers insert this instrument’s lighted, optical shaft into a hole usually about 1⁄2-inch in diameter, in the exterior wall system. Using this device, engineers can visually assess problems, including mortar droppings in wall cavities, wet insulation, and poor flashing installation — corrosion of connections behind the exterior cladding without making large openings in the wall or removing pre-cast concrete or stone wall panels.

— Matthew P. Kutzler and Mark E. Leeman

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  posted on 6/1/2007   Article Use Policy

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