Moisture intrusion happens for various reasons; roofing for one. The different roofing industry, design and maintenance players seem to stress roof failures based upon their own perception or agenda. This prompted a survey and confirmation with several industry experts’ to determine the percentages of each failure cause. These causes should emphasize our focus and goals for minimizing failures of the construction, manufacturer and design industry. Commercial and Institutional roof failures can be categorized into five major culprits: installation, materials, design, wind uplift and maintenance.
INSTALLATION is the cause of 80% of roof failures. It is the number one contributor and should be the major not the only focus for continuing education and verification goals. Recommendations to minimize installation failures are:
Implement designer interface flashings correctly. If not shown or insufficient demand them. Interface details with other trades and products are one of the major causes of roof failures. General contractors need to provide a weather tight building enclosure. Weather tightness depends on the interface details and their process. The process cannot be violated. For example, if an interface between multiple planes and multiple products converge in one location, there is or should be an established sequence for the constructing of it. And yes, a trade may have to come back and complete their work if they get ahead of the schedule or another trade’s work is incomplete. The need for weather resistant surfaces and flashings has to be continuous, sloped and sheds water. The consequences are serious; compromises generate failures and long term owner maintenance, health concerns and energy deficiency issues.
Eliminate the mixing of trades. Sometimes contractors’ means, methods and contract negotiations mix trades to their own detriment. For instance, a roofer or mason have acceptable flashing components within their products’ scope yet they are not tinsmiths and incapable and should not be performing a tinsmith’s role on complex flashings if there is soldering involvement..
Avoid the low bid process and unrealistic schedules to improve craftsmanship and quality results. Low bids foster higher risks, cutting corners and quality, such as incomplete submittals, limited craftsmanship and supervision. Owners will never achieve an energy efficient building enclosure with a low bid process unless there is adequate verification, special inspections, full time inspections while product is being installed. Bidding process should be based upon credentials, experience and reputation.
Verify. Architects need to specify critical notifications and verify product installations. Owners need to adequately subsidize architects and/or consultants so they can provide focused construction observations. It is not the quantity of visits but establishing and verifying specific predetermined sequences with 48 hour contractor notifications before covering up by other trades or interface connections.
Eliminate ponding. The less ponding on a roof, the longer it lasts and fewer leaks develop. Ponding water magnifies sunlight and collects dark particles which absorb heat. Best practice is that every roof should slope; the more, the better. It’s a roof; everything should slope to drain. It does not matter whether it is a low slope, vegetative roof or a plaza deck over occupied space, it should slope. Any obstructions to the travel of moisture should be addressed. For example, roofing contractors need to trim low slope, walkway pads at valleys to allow drainage.
Protection of the roof during the construction process is often specified with minimal success. The staging requirement for mechanical penthouses or roof mounted equipment is a major source of damage. The best practice is to exclude penthouses or roof mounted equipment and accessories, minimizing human traffic to once or twice a year. It could improve the roof life and maintenance requirements by 25%-50% over the life of the building.
Educate more, minimize errors and repairs. Contractors and designers who are proactive in educating the construction team will spend less time documenting, corresponding and overseeing repairs.
Verify more, fix and patch less. Contractors and owners who are more proactive in understanding product requirements and verifying during construction will spend less time fixing problems.
Require project-specific product installation details for approval. Unfortunately, the submittals are pulled together by the roof contractor from a manufacturer’s catalog which are not project-specific; creating confusion and failures.
Roofing contractors need to provide submittals that include interface details, coordinated with other disciplines showing how they interface. Architectural specifications request them yet contractors rarely comply. It is up to the general contractors to enforce them. Uncoordinated submittals are a good indicator that the general contractor and his subs are not meeting and coordinating their work, resulting in a problematic roof.
Require craftsmanship. Craftsmanship and diligence of each individual affects the installation quality. Apprenticeship programs, developing experience while working on the job, can be effective when adequately supervised by experienced craftsman. Lack of craftsmanship and knowledge is the ultimate reason for most roof failures.
Implement realistic schedules. This is a major contractor challenge as it takes only one sub to affect the project schedule and sequence of work.
Implement construction sequencing that does not compromise roofing, penetration flashings and interface flashings.
Provide roofing mockups, especially interface between materials. Mockups, if designed in a layered display are an excellent educational tool. It should minimize installation problems normally encountered in the field. A good roofing mockup should address interface with wall moisture barriers, penetrations, roof edges, etc. that are specific to the project.
Verify roofing contractor’s installation of their wind uplift design. During the roofing contractors installation their work needs to be verified at specific sequences for compliance; such as fastener type, layout and number. It should be field tested.
The other four of the five culprits will follow in future articles.