When the paint on the exterior of a building exhibits heavy fading, chalking, or peeling, the typical solution is to clean and overcoat, but painting alone may not achieve the desired result, and in fact, it may be destined to fail. Because a number of building-related issues can affect the performance of the coating system, they should be identified and repaired before the painting begins. Typical building-related issues of concern on masonry commercial buildings include the condition of the mortar and block, sealants and joints, weeps, and gutters and downspouts, as discussed below.
Note that if the failure of the existing coating system involves moisture intrusion, different types of forensic inspections and repairs need to be performed. Those issues will be addressed in a future article.
Cracked Block And Brick
Any objectionable crack should be analyzed to determine the cause, and the need for corrective measures. When objectionable cracks are observed, information such as the pattern and location of cracking should be documented and discussed with a structural engineer. If cracks appear to be related to settlement, a civil or geotechnical engineer may also be required. Settlement cracks are often diagonal or stair-step and originate near the finished floor level. Cracks that become a structural concern, such as settlement cracks, sometimes require extended observation. A crack-width monitor can be installed to observe changes in width over time. Additional evaluation is typically required when there is excessive cracking in the structure. Evaluation may include nondestructive inspection such as thermal imaging to detect the presence of wall renforcing, or inspection with fiber optics such as a boroscope, to assess the interior of wall cavities. Inspecting the walls for cracks is not only important for control of moisture and performance of the paint, but is also critical for the structural stability of the wall. Cracks have many causes, including thermal or moisture expansion, impact, misuse of structure, inadequate support for wall openings, and foundation settlement. Random cracks can be dynamic and move during weather changes or changes in stress, while other cracks can be static.
Depending on the building design and type of damage, repairs or additional structural support or replacement may be necessary and included in the restoration scope of work.
Small moving cracks that do not pose a structural problem should be repaired to prevent water penetration from wind-driven rain. Cracks can typically be placed into two categories, cracks less than 1/16-inch and cracks greater than 1/16-inch. Cracks less than 1/16-inch should be cleaned using a utility knife and filled with flexible crack filler. Cracks greater than 1/16-inch should be prepared by routing with a v-notch or a grinding wheel. Once routed, a urethane sealant capable of withstanding high movement should be installed. Sealant width and depth should be a minimum of ¼-inch x ¼-inch. Avoid installing a rigid repair material, such as mortar, in moving cracks. Rigid materials in moving cracks will inhibit movement, causing more cracks to form in other areas.
|Fig. 1: Stair-step cracking near the parapet may be an indication of potential structural problems.
Mortar joints in masonry walls can deteriorate over time, allowing moisture to migrate into the structure. Cracking within the mortar is caused by excessive moisture, excessive freeze/thaw cycling, and poorly mixed mortar. Mortar joints should be examined to confirm that they are solid and intact rather than soft and deteriorated (Figures 2 and 3). Figure 2, for example, shows excessive moisture in the joint and the growth of moss. The mortar is also layered, which is a typical sign of excessive freeze/thaw cycling. If deteriorated joints are fairly stable in width, they can be repaired by conventional tuck-pointing (or repointing) prior to the installation of the coating system. Tuck-pointing should be performed by completely removing all loose and deteriorated mortar and installing new mortar that matches the existing mortar type and strength. National Concrete Masonry Association (NCMA) Tech Note 08-1A provides helpful guidance on proper sequencing and installation for tuck-pointing activities.
|Fig. 2: Layering within mortar joints, typically caused by freeze/thaw cycling. Moss is also present.
|Fig. 3: Large area of deteriorated mortar joints in need of tuck-pointing.
Damaged block commonly occurs from impact. Block that is gouged, scraped, or perforated should be repaired before painting (Figures 4 and 5). Non-structural repairs in masonry units can commonly be accomplished using a non-sag, modified masonry repair patching material. Caulks and sealants should not be used for repair as they provide only a temporary fix.
|Fig. 4: Scrapes and gouges in block should be filled prior to painting.
Repair materials are available for use in abrasions down to a depth of 1/8-inch. The size of the hole or abrasion will govern the specific type of repair material that is used. Elements of the conventional wisdom about repair material follow, but it should be noted there are exceptions:
- Feather-edging of repair materials is discouraged.
- The materials can accommodate repairs up to 6 inches in diameter.
- Admixtures and primers are required to achieve proper adhesion of repair materials, especially for shallow repairs.
- Common repair materials can be placed in lifts between ¼ inches to 2 inches with the appropriate admixture and bonding agent.
- The repair mortar is allowed to stiffen before applying the next lift.
- In the case of block that has an open web as shown in Figure 5, the void should be filled with closed-cell foam or material that will not absorb moisture. This will prevent repair materials from falling inside the cavity during installation.
- As always, refer to the manufacturer’s product data sheet for recommended installation procedures.
|Fig. 5: Holes in block should be repaired prior to painting, or the block face replaced.
For repairs over 6 inches in diameter, it is typically best to remove the outer face of the block and replace with a new block face. In addition, patching damaged block is sometimes not an option due to aesthetics. When patching is not an option, the damaged unit can be removed by chiseling or saw-cutting the damaged unit and surrounding mortar. A new unit can be installed by applying mortar around the edges and retooling the joints after it is placed.
Spalled Block or Brick
When block or brick become saturated with moisture that cannot escape through the coating system, spalling can occur under freeze/thaw conditions (Figures 6 and 7). In some cases entire bricks can become detached from the mortar bed. When spalling is present, the source of moisture intrusion should be determined prior to cleaning and painting. (This can involve an exhaustive series of evaluations and tests, and will be discussed in a future article.) Once the moisture problem is resolved, block repairs should be completed before cleaning and painting begins. For minor spalls, a masonry patching material can be used to smooth out surface spalling. Deeper spalls (typically ¾ inches in depth or greater), such as the one shown in Figure 6, often require the removal and replacement of entire sections of block or brick. Random spalling is typically not a structural concern if the masonry wall is in running bond. If entire rows or sections of block have deep spalls, additional support or modifications to the wall may be required and a structural engineer should be engaged. Due to aesthetic concerns, spalled brick veneer, as shown in Figure 7, may require removal and replacement of the entire brick.
|Fig. 6: Spalling of block is an indication of moisture intrusion that needs to be addressed prior to painting.
|Fig. 7: Spalling of brick face.
Sealants At Vertical Joints
Both vertical and horizontal joint sealants need to be maintained in barrier walls to prevent entry of moisture and bulk water from rain events. Soft joints are installed in expansion joints, perimeter of openings (doors and windows), around decorative features and pop-out walls, and at flashing tie-ins. Sealant joints are also required around pipes, conduits, and other penetrations through the wall.
The joints should be inspected for both adhesive and cohesive cracking. Adhesive cracking occurs when there is separation between the wall and sealant material. Cohesive cracking occurs when the sealant itself cracks. Cohesive cracking results when the material is stressed beyond its maximum movement capability and the adhesion strength exceeds the tensile strength. The sealant should be replaced when these types of cracks are observed (Figure 8). During inspection of the sealant, the joint backing or backer rod should also be examined. Open-cell backer rod should be not be used as it can retain moisture (Figure 9).
|Fig. 8: Cracked sealant should be removed and replaced.
|Fig. 9: Open-cell backer rod should not be used.
When cracking is present, the existing sealant should be completely removed and the joint or surface must be clean and dry before new material is installed. Typically, a urethane sealant capable of high movement is used in wall joints, junctions, and penetrations. A compressible, non-gassing, closed-cell polyethylene foam rod is typically used as joint backing for sealants. The joint backing should be properly sized to the joint width. Sometimes, a sealant primer is necessary prior to application of the sealant to increase adhesion properties, especially when applied to materials that have a smooth surface, such as metal or tile. The sealant should be adhered to both sides of the joint, but not to the back, to prevent three-sided adhesion (except when backer rod is present). The sealant must have the proper width-to-depth ratio as indicated in the building specifications or technical data sheets to allow for optimal elongation. It must also be tooled properly when installed.
Sealants At Base Of Walls
The junction between the base of a wall and a concrete slab should be sealed to prevent rain water or water from cleaning operations from saturating the base of the wall (Figure 10). Gaps or openings in this area are often larger than those found in vertical joints. Typically, fibrous expansion joint material ½ inch to ¾ inch thick is installed before concrete is placed. Over time, the expansion joint material will decay, leaving a large gap between the concrete and the wall. Often, self-leveling, two-part polyurethane sealants are used for horizontal sealant applications in concrete.
|Fig. 10: Deteriorated sealant between the base of a wall and concrete stairs needs to be replaced.
Proper design, installation, and maintenance of flashing are important for the control of moisture in masonry buildings. Flashing deficiencies are normally the most common source of roof problems and can result in leaks inside the building and excessive moisture in walls. Flashings in walls are also important, with their primary role being to intercept the flow of moisture through the masonry and to direct it to the outside. Flashing failures typically stem from lack of detail, either by the designer or the installer.
There are many flashing types and locations where flashings are used on buildings. Flashings can be metal or flexible membranes. Modern buildings often have unique components such as canopies, parapets, signs, and structural support members that require some type of flashing. Flashings can be fully exposed, partially exposed, or concealed within the wall.
It is important to understand how moisture is managed through flashings prior to cleaning and painting activities, and whether they are functioning. Exposed flashings such as parapet caps and reglet flashings at roof tie-in’s (See Figures 11 and 12) can be visually inspected from the roof, a lift, or a ladder. Partially exposed flashings, such as for cavity walls, door and window openings, and sills, sometimes require destructive inspection or inspection with fiber optics (boroscope) to identify the proper location of the flashing. Figure 13 shows where a cavity wall flashing was not installed behind EIFS cladding material above a concrete sill. Flashings such as through-wall flashings, end dam and corner flashings, and membrane flashings behind cladding that permit drainage to the exterior are frequently hidden. Sometimes, the symptom of missing or improperly installed flashing can reveal itself through localized efflorescence and peeling paint, initiating the need for further investigation.
|Fig. 11: Counter flashing not installed on wall at canopy tie-in.
|Fig. 12: Galvanized parapet cap corroded and not sealed at seam.
It is important to ensure that flashings are kept intact and properly functioning to allow for proper moisture control. If flashing deficiencies are identified during assessment appraisals, they must be addressed prior to cleaning and painting activities to prevent ongoing moisture problems and premature coating failures.
|Fig. 13: Concrete sill moved to allow for an inspection of flashing. Flashing not installed behind the cladding.
A wall drainage system may include through-wall flashing that directs water flow to a series of weep holes. Weeps are small openings in the outer wall of masonry that serve as outlets for interior water to move outside to evaporate. The weep system is mostly concealed inside the wall except for the drainage ports that are visible on the outside. Drainage ports can simply be an open hole, a rope, or a manufactured plastic or metal spout. It is important that the drainage port is not obstructed so that water can escape to the outside of the wall. Moisture stains or efflorescence visible underneath the weeps are a good indication that the wall drainage system is properly functioning. However, excessive stains or efflorescence may be an indication of more significant moisture problems in the wall that should be examined. Obstructions in the weeps are important to note and must be corrected for the drainage system to function. Obstructions can be in the form of paint, caulk (applied intentionally without understanding the purpose of the weeps), mortar (from initial construction falling onto the pans and clogging the weep—as shown in Figure 14), and dirt.
|Fig. 14: Mortar blocking weep, preventing moisture from escaping.
When obstructed weeps are identified, the weep ports should be cleaned. If rope weeps are used, paint or caulk must be cleaned from the exposed ends. If open holes or manufactured weep spouts are used, any grout, sealant, or other contaminants visible in the drain spouts should be routed out with a drill bit or similar method. Care should be taken not to drill through the drain pan while cleaning out the spout. If cleaning the weep is not effective in providing drainage, it suggests that the drain pans are clogged (e.g., with mortar from construction). If the drain pans are clogged, the problem can be remedied through the installation of retrofit through-wall flashings and end dams to facilitate proper drainage. Retrofit pans and flashings can be a labor-intensive process, but may be necessary to prevent ongoing moisture problems and premature coating failures.
Deficiencies in roof drainage systems, such as ineffective gutters and downspouts, are frequently responsible for problems with the performance of exterior coating systems. When the gutters and downspouts are damaged and clogged, the coating system experiences an immersion-like exposure to a large volume of water that leads to paint failure and moisture intrusion. Common deficiencies in roof drainage may include corrosion of the gutter, poorly sealed lap seams in gutters and downspouts, and impact damage. Defects in the gutter system (Figures 15 and 16) must be corrected; otherwise, coating failures will continue to occur.
|Fig. 15: Breaks in gutter seam will cause this newly applied system to fail prematurely.
|Fig. 16: Gutter corroded on bottom, allowing water to cascade down the masonry wall.
If the existing coating exhibits water-filled blisters, extensive peeling, and widespread streaks of efflorescence, a more detailed examination of the building should be conducted to determine if there is a moisture intrusion problem. If so, the problems should be corrected prior to painting. Examinations include wall moisture measurements (surface and within the wall cavity with different types of moisture meters); inspection of the termination of the roof membrane over the parapet and the condition of the coping; air leakage tests to examine air infiltration and exfiltration at the roof/wall junction and around and above openings such as doors; infrared thermography to detect the presence of insulation, excessive moisture and air leakage; use of fiber optics (borescopes) to determine the wall cavity condition; wind-driven rain resistance of the existing coating or waterproofing material; and removal of coating samples for laboratory analysis of coating type, thickness, and condition. These tests will be described in a future article.
There are a number of building repairs that should be performed as part of, or prior to, a repainting project in order to improve the aesthetics and performance of the coating. Sometimes, building repairs are overlooked or simply not initiated due to cost, but if the necessary repairs are not completed, the coating can fail. When this happens, the coating manufacturer and coating applicator are often blamed, even though the problems are outside of their control. All parties involved should be aware of the risks associated with not executing building repairs prior to repainting.
Some owners take a proactive approach when it comes to maintaining the exterior of the building. NCMA Tech Note 08-01A provides a recommended schedule for visual assessment of the exterior of masonry structures. This information is presented in Table 1 and can also be found on the NCMA Website at www.ncma.org. Timely identification of problems can greatly reduce the costs associated with corrective measures. A proactive inspection plan can lead to increased service life of the building asset and prevent unwanted moisture problems and coating failures.
Table 1 – Maintenance Schedule (source NCMA Tec note 08-01A)
|Check the overall appearance of the structure for any signs of damage or malfunction to the exterior.
|Inspect mortar and units. Ensure intimate contact between mortar and units. Check for the presence of cracks, chips and other surface degradation.
|Check plumb and vertical alignment of wall surfaces.
|Every 2 to 5 years
|Check for the presence of dirt, stains, efflorescence, and graffiti and clean as necessary.
|Examine flashing and weep holes to ensure proper function. Repair screens as necessary.
|Examine the condition of sealants at the control joints.
|Examine the condition of the caulking materials.
|Check for locations and sources of moisture.
|Check for ivy and its effects on the masonry.
|Examine the condition of coatings.
|Examine the condition of the parapet cap and copings.
|Examine the condition of the roof membrane.
|Check the condition of the roof drains, gutters, downspouts, and splash blocks. Clean and repair as necessary.
|Spring and Fall
|Check to make sure that the ground slopes away from the building on all sides.
|Check the size of trees and shrubs near the building.
|Check for the presence of insects and vermin. Remove nests and clean weep holes as necessary.
|Verify adequate anchorage and performance of sign, porch lights, etc. attached to the exterior.
|Inspect for signs of water leakage and mold growth.
|Check plumb and vertical alignment of wall surfaces.
|Every 2 to 5 years
|Examine the condition of the sump pump and French drain.
|Windows and Doors
|Examine flashing and repair as necessary.
|Examine caulking or weather stripping and replace as necessary.
|Feel for drafts and look for signs of possible water entering the structure.
|Examine chimney for loose masonry units or mortar.
|Have chimney flue inspected and cleaned.
About the authors
Kevin J. Brown is manager of the Commercial Services Group for KTA-Tator Inc., where he develops and implements maintenance programs for commercial clients with architectural/commercial problems related to paint failures. He is a Certified XL Tribometrist, with more than 12 years of experience in the field of retail facility management, overseeing building maintenance and preventative maintenance programs for more than 1,700 stores including store repaints, floor coating replacement and long-range budget planning. He has extensive knowledge of numerous protective-coating systems, tooling/floor polish processes, and construction-drawing building-code review. Brown utilizes KTA’s professional staff and independent laboratory to conduct a variety of consulting services, including coating failure analysis, specification development, coating-condition surveys, floor-polish evaluations, roof-detail inspections, paint-performance testing, and program management.
His previous experience includes managing numerous building maintenance and preventative maintenance program projects such as store re-painting, floor polishing, floor caulking, polycarbonate replacements, lift stations, and pest control.
He has a bachelor’s degree in business administration and an MBA from Gardner-Webb University, has been a featured guest speaker at various trade-association conferences including SSPC (The Society for Protective Coatings), contractor workshops, and lunch-n-learn presentations for national A/E firms.
Kenneth A. Trimber is president of KTA-Tator Inc. He is a NACE Certified Coatings Inspector Level 3, is an SSPC Certified Protective Coatings Specialist, and is certified at a Level III coating inspection capability in accordance with ANSI N45.2.6. Trimber has 40 years of experience in coatings inspection, testing, and analysis, is a past president of the Society for Protective Coatings (SSPC), and is chairman of the SSPC committees on Surface Preparation, Visual Standards, and Containment. He is also past chairman of ASTM D1 on Paints and Related Coatings, Materials, and Applications. He is the author of The Industrial Lead Paint Removal Handbook and co-author of Volume 2 of the Handbook: Project Design. Trimber is chair of the newly formed SSPC Commercial Coatings Committee (Architectural, Commercial, Institutional). He is a recipient of the John D. Keane Award of Merit, was named a JPCL Top Thinker in 2012, and is a past technical editor of the Journal of Protective Coatings and Linings.
Durability + Design: The Journal Of Architectural Coatings ©2013 Technology Publishing Company