The Key to Healthy Exterior Walls
By Stephen Varone, AIA and Peter Varsalona, PE
A building’s exterior walls protect the interior living spaces from a constant barrage of natural forces, including rain, ice, hail, wind pressure and suction, fluctuating cold and heat, ultraviolet degradation, air contaminants, vibrations, and even vandalism. Deterioration is inevitable no matter the materials that comprise the walls, whether it’s brick, stone, stucco, EIFS, wood, steel, glass, or a rain screen system. Over time, exposure to the elements, lack of maintenance, improper repairs, and/or poor construction and design can all lead to leaks, cracks, rust, dry rot, and ultimately failure of the wall system.
When the building envelope is compromised, not only can quality of life for occupants be threatened, but cracked or crumbling facades diminish property value and, at its worst, can affect a building’s structural integrity and pose a safety hazard to the public.
Exterior restoration projects can be a challenging undertaking, given their often hefty costs and lengthy timelines. Not surprisingly, building boards and managers try to put them off until absolutely necessary, usually when water infiltrates apartments or when an unsafe condition is discovered and the law requires them to take action. Deferring work until it’s unavoidable or attempting an easy fix can, however, exacerbate the underlying issues and become even more costly in the end.
The key to maintaining a healthy wall is identifying, properly diagnosing, and repairing problems before they become serious.
Deterioration: Common Symptoms
Recognizing early indicators of deterioration and developing proactive repair programs are critical to good management of the building envelope. The most common and persistent cause of wall failure is water infiltration, which most often occurs at poor mortar joints, cracks in the masonry, and failed or improperly installed flashing at the parapet walls, door and window details. When moisture penetrates the building interior, it can cause water damage, possible associated mold growth, structural degradation, and even structural failure. Some common symptoms are:
Efflorescence is a white powdery residue that appears on the surface of masonry walls. It is an easily recognizable indication of water penetration in brick, stucco, concrete, and mortar. It occurs when salts and minerals within the masonry dissolve in water and migrate to the surface. Unsightly and difficult to clean, efflorescence may not pose an immediate risk, but its continued presence should warrant further investigation.
Fungus and other vegetative growth, such as moss in mortar joints or on brick, is another sign of the presence of excess moisture. Such organic growth attracts and retains moisture, accelerating masonry decay.
Cracking, spalling, flaking, or peeling of masonry surfaces can be symptomatic of a number of different problems, ranging from cosmetic, low-risk conditions to ones that are severe, dangerous, and costly to repair.
Building materials expand and contract depending on their characteristics and the effects of factors such as moisture content and temperature variations. For example, brick expands over time, concrete shrinks, and steel expands when it corrodes. Repeatedly expanding and contracting masonry can develop cracks, which then enlarge over time. The freeze/thaw cycles that are prevalent in the northeast cause cracking and spalling in masonry when moisture infiltrates, then freezes and expands. Left unchecked, spalling can cause large sections of masonry to crumble and fall off, and small cracks can quickly develop into larger ones that lead to more serious structural damage.
Poor design, inexpert workmanship, and use of improper or defective materials in the original construction of a building or a previous repair can all be contributing factors to severe wall deterioration.
Bulging Walls. A perceptibly bulging or out-of-plumb wall indicates movement of the masonry and should be promptly evaluated by a qualified structural engineer because of the potential for structural failure. Bulging is typically caused by pressure exerted when masonry expands from moisture absorption and freeze/thaw cycles. It can also occur due to improper masonry anchorage, and/or a lack of proper expansion joints.
Mortar deterioration. In brick, cement, and stone masonry, mortar binds the masonry wall together at mortar joints. When mortar joints erode, cracks are visible, the mortar is soft or crumbling, or if mortar is missing, the exterior wall becomes vulnerable to water infiltration. Mortar deterioration usually occurs from the natural action of wind and rain erosion, moisture penetration, and are also sometimes due to faulty construction and/or design.
Attack the Source
Superficial fixes often end up costing much more than they save. Quick remedies for water infiltration, such as surface patches and tar seals, may at first seem to solve the problem, but they more often than not worsen the situation by trapping and sealing water within the walls. Misguided repair attempts that fail to address the source of the failure can turn a small issue into a costly disaster.
What may seem on the outside to be a simple wall is actually a composite and complex system, composed of different materials and components that work together for weather protection and structural integrity. Whenever there is a question as to the cause of exterior wall problems, a qualified engineer or architect should be brought in to conduct a comprehensive evaluation that identifies the underlying problems and recommends a course of action.
Misguided repair attempts that fail to address the source of the failure can turn a small issue into a costly disaster.
The engineer/architect will typically begin with a visual examination of the exterior walls for signs of distress. A leakage survey is also often distributed to residents to help determine the extent that water has penetrated the building envelope. Upon completion of the visual examination, it might be determined that physical testing is necessary. Some of the more common testing tools include a non-invasive hand-held meter to measure moisture, and infrared thermography to detect and pinpoint leaks by observing thermal differences. If serious cracks are observed, crack monitors may be installed to accurately measure the change in crack width over a period of time. However, when non-destructive testing does not yield definitive results, a probe investigation to expose underlying conditions is typically warranted.
After analyzing the results of the investigation, the engineer/architect can develop detailed recommendations to address the problems at their source. To help boards and owners develop a budget and determine a course of action, the proposed remedy should always include a prioritized scope of repair, preliminary budget projections, and an approximate timeline.
For buildings with little or no severe issues, recommendations can sometimes be as straightforward as cleaning and refinishing to help refresh and extend the life of the facade. Buildings in urban areas in particular are subjected to pollution, soot, exhaust, and other detritus that adhere to the walls and not only diminish the appearance of the building, but can advance deterioration.
At the other end of the spectrum, when fixing the current facade is not an option, a drastic overhaul such as a reskinning, which involves removing and replacing the entire exterior of the building, may be required. While a costly endeavor, reskinning can sometimes be the more cost effective long-term solution, especially when air and moisture leakage affects building performance. A new, up-to-date facade can reduce maintenance and energy consumption, thereby lowering a building’s annual operating costs. An added benefit is that reskinning can also breathe new life into a building and enhance its appearance, making it more attractive for existing and potential residents.
Preventive Maintenance
Eventually, time catches up to all buildings. Thanks to local laws requiring inspections of buildings over six stories every five years (what is known in New York City as the Facade Inspection Safety Program, or FISP, formerly Local Law 11), city streets are safer than ever. However, exterior wall deterioration can develop in a relatively short period of time. Failure in any one part of a wall system can quickly affect other components and increase the risk of failure.
By inspecting walls regularly, areas of minor deterioration can be detected and repaired before they escalate into severe, costly problems. Routine upkeep and preventive maintenance/repair are not only crucial in promoting the longevity of a building, but can also improve performance, and keep the exterior envelope looking fresh and attractive.
Stephen Varone, AIA is president and Peter Varsalona, PE is principal of RAND Engineering & Architecture, DPC. This article was reprinted from the February 2018 issue of Habitat Magazine.