May 2019 — A good roofing management program extends the life of roofing and maintains its ability to perform. Without such a program, leakage and property damage are likely, with repairs and replacement scheduled by crisis rather than by design.
A roofing management program starts with organized record keeping at the time of initial design. The original plans and specifications, including load capacity, code requirements, drainage, R- value of insulation, material specifications, and warranties, should be part of these records. In addition, as-built details and minutes of preconstruction conferences should be recorded. An estimate of the replacement cost of the roofing system is necessary because the roof is a depreciable asset that will eventually require replacement.
Why Roofing Fails
Most roofs are hidden from view. Roofs and roofing often receive minimal attention until a leak occurs, indicating a roofing failure. Roofing fails for seven principal reasons:
- Poor installation workmanship
- Inadequate inspection and maintenance
- Improper design
- Faulty materials
- Improper use
- Cleaning and maintenance damage
Poor installation workmanship is probably the primary cause of early roofing failures. Inadequate inspection and maintenance accounts for most failures of roofing after the first year or two.
Because workmanship at the time of installation is critical, care should be taken to select a qualified roofing contractor. To prequalify contractors, look for those with adequate resources and good reputations who are approved by material manufacturers. When possible, use an experienced quality assurance inspector.
A building that has a curtain wall in its design and construction often faces issues in regards to cleaning and maintenance. A contractor will often be procured to provide these services.
When cleaning and maintenance services are required the contractor will use equipment on the roof that can damage the roof and parapets. Window washers may tie off of equipment as they lower platforms on the curtain wall. Building managers must preplan for window washing activities on their roofs.
The most important reason for establishing a program of regular roofing inspection and maintenance is to protect the investment in the building and its contents. An effective maintenance program will not only add years to the life of the roofing, but will also detect minor problems before damage is widespread and the internal functions of the building are interrupted. You should not wait until the roof is leaking to begin a roofing maintenance program.
A roofing system is exposed to numerous physical and chemical stresses. The long-term effects of these forces are considered normal aging. In reality, small isolated problems occur as a result of abuse, stress concentration, installation errors, or other factors. These apparently small problems, if unattended, escalate over time until they are extensive and expensive to fix and will ultimately shorten the life of the roofing.
A properly functioning maintenance program is part of a cash management program. When roofing reaches the end of its life cycle and is no longer economical to maintain, it can be replaced in an orderly fashion, if the requirement for replacement capital has been anticipated and budgeted.
Historical information is a must for each building, or, in the case of complex structures, each roofing section.
Armed with a roof plan and information collected from the historical file, building maintenance personnel or a competent roofing contractor, consultant, or roofing materials representative should conduct regularly scheduled visual roofing inspections. Checklists can help to ensure comprehensive and consistent inspections.
A walkover should be scheduled every month or two. The main objective of this walkover is to pick up litter, especially around roof drains. Accumulations of dirt or stack-exhaust particulates should also be removed at this time.
Before a roofing inspection is conducted, the structure itself should be visually inspected. Exterior walls frequently indicate signs of movement that may be related to roofing problems. Water stains, for example, might suggest problems with gravel stops, flashings, or copings.
During inspections, every component of the roofing system should be closely checked. Evidence of deterioration should be noted, as well as rooftop traffic patterns, signs of poor drainage, and collection of debris. The semiannual visual inspection may include minor maintenance, as well. This includes such tasks as refilling pitch pockets with roofing mastic and reattaching loosened flashing fasteners.
Determine the composition of the roofing system—that is, whether it is a bituminous, elastomeric, or some other kind of roof. Is the membrane the original one or a re-cover? Are there patches or problem areas? First impressions of the roofing appearance should be documented in writing, noting such problems as collections of debris, clogged drains, and ponded water. Heavy traffic on the roof may require protective traffic pads. Bare spots on bituminous roofing may be due to wind sweeping, flow of the flood coat, or blistering. These bare spots can seriously affect long-term performance and should be re-coated.
Common Membrane Roofing Problems
The most common problems affecting membrane roofing, as found in the field, are listed below with their causes.
- Blistering: Thermal expansion of trapped air or water vapor over wet insulation or in areas of poor adhesion
- Cracking: Breaks in unsupported felt; cracking of blisters or ridges by traffic; breaks at sharp bends in felt
- Splitting: Stress concentrations resulting from inadequate or nonuniform attachment; flexing at moving joints from temperature changes, membrane shrinkage, fatigue
- Buckling: Movement of the felts or substrate under thermal effects, causing long, rippled ridges
- Lifting: Poor adhesion along the edge of felts, resulting from wrinkled felt or poor edge embedding
- Punctures: Breaks in the membrane from broken blisters, nails backing out of the deck, dropped objects, ladders placed directly on the membrane, hail, or lack of membrane support
Terminations and connections to a roofing system require careful examination. Flashings should be inspected for damage, shrinkage, splitting, and looseness. Counterflashings must overlap the base flashing sufficiently to prevent wind-borne water from entering.
Uncovered pitch pockets or pitch pans are no longer recommended. Existing uncovered pitch pockets are troublesome because the filler shrinks with age. The level of filler should be checked at every inspection.
If uncorrected, each of these conditions will worsen, leading to water leakage into and through the roofing, eventually resulting in roofing failure.
Contractual Surveys and Roof Maintenance
It is beneficial to establish a program of maintenance and inspection with a reputable local roofing contractor. Typically, such a contract includes visual inspections of the entire roof area twice each year: once in the spring, and again in the fall. The contractor prepares a report on conditions, including recommendations for needed repair or maintenance work and an estimate of the cost. Upon authorization, the contractor completes the work.
Moisture surveys might be conducted at the completion of a roofing project to confirm that the roofing system is dry, and again shortly before a roofing contractor’s warranty expires. On existing roofing systems, a moisture survey should be conducted when the roofing file is compiled, and then periodically (every two to five years). They are desirable supplements to visual inspections. The purpose of a moisture survey is to determine how much moisture is in the insulation under the membrane. Saturated insulation can result in leaks in areas of the building other than where the roof is leaking. Replacement of this insulation is a costly repair.
NDE (Nondestructive Evaluation)
Moisture surveys use such different methods as infrared thermography, nuclear backscatter, or electrical conductance. These are major methods for nondestructive evaluation (NDE). Each method identifies wet insulation, but does not necessarily find the source of the moisture (that is, the actual leak). Identifying the relative moisture content of each section of the roofing helps produce a relative moisture content map of the roofing. The wettest area can be selected, and a core sample (a small section of the full depth of the roof) is tested to determine the actual moisture content. An informed evaluation can then be made about the condition of the roofing and any remedial action required.
Moisture trapped in a roof can build up enormous pressures, approaching 400 psf, as it vaporizes. The resulting blisters delaminate the built-up roof membranes, separating plies from one another, from substrates, and from the flood layer surface. Blisters also crack and split, increasing the possibility of leakage and inviting wind damage.
There are two basic methods of minimizing moisture entrapment in a built- up roof:
- Ventilate the plenum beneath the roof.
- Install vapor barriers, normally between the roof deck and the insulation layer (if there is one) or the roofing membranes.
This article is adapted from BOMI International’s Building Design and Maintenance course, part of the SMA designation program. More information regarding this course or BOMI International’s new High-Performance Sustainable Buildings credential (BOMI-HP™) is available by calling 1-800-235-2664. Visit BOMI International’s website, www.bomi.org.