Building Strategies to Prevent Water Intrusion
By Eric Lambert, from FMI Quarterly
Avoid the “water, water everywhere!” call during construction.
An improperly installed soap dispenser fell onto a lever-style faucet causing water to run over the weekend, flooding the three floors below and resulting in $350,000 in damage.
Rainwater entered an 11-story building through a broken roof drainpipe and unprotected window openings. The water ran throughout the building via elevator shafts, causing $217,000 in damage.
Workers carrying a large ladder inadvertently knocked sprinkler heads that were already hooked up and a shut-off wasn’t available, causing thousands of dollars of damage.
Water damage events like these during construction are one of the top risks for contractors according to Zurich loss data for general liability and property losses. They can be expensive, difficult to fix and result in weeks or even months of construction delays.
The good news is that strategies to prevent water intrusion from either exterior precipitation or interior plumbing systems are not necessarily expensive, and more a matter of careful planning and regular weekend and off-hours, job-site inspections.
Taking the proper time to put simple and often inexpensive water mitigation processes in place during pre-construction, construction and post construction can help save contractors from the headache and expense of rework and replacements after an event.
The War on Water
Any construction project requires waging a “war on water” — creating effective strategies and tactics to keep away sources of wetness, including groundwater, water table, floodwater, seepage, storm water, utilities, sewers, snow/ice melt and runoff or discharge from adjacent properties.
To minimize damage, international construction services firm Turner Construction develops a moisture control plan in conjunction with its site logistics and storm water plan for each company project, said Michael Blackburn, Turner’s safety director for the Great Lakes Region.
He said the plans focus on addressing the exterior envelope detail, particularly during the project constructability review; incorporating temporary protection into the scope and estimate for the project; closing in the building prior to starting drywall; starting up permanent air handling systems as soon as possible to aid with climate control while installing interior finishes; and quickly responding to water incursions, should they occur.
“Turner’s proactive moisture control plan helps reduce the risks of water intrusion into the building and aids in controlling moisture in the building and surrounding areas,” Blackburn said. He added that any water intrusion plan should address a project’s entire life cycle — before, during and after construction — and requires a great deal of coordination.
Make Planning a Priority — Before, During and After
During pre-construction, members of the project team should work together to uncover the potential sources of water intrusion. One focus should be on identifying the likely rainfall frequency and volume for the location in order to schedule work around these periods.
That team should also identify water sources on or around the site, like sewers, its water table and utilities, and develop plans or practices to control each source during building. Contractors should work closely with architects, designers and engineers during this phase to avoid building a structure that could have inherent water infiltration problems.
“It is important for the designer, contractor and owner to collaboratively establish a plan to guide development of solutions to minimize the risk of water intrusion on a project. Collaboration early in the project is important so that all team members have an understanding of the project scope and establish methods to manage the risk of moisture on a project,” Blackburn said.
The designer should provide a construction document with adequate details related to potential water damage; the contractor should use best practices in controlling the impact of water during construction; and the owner should recognize the importance of protecting the building envelope through rigorous inspections and testing.
Beyond the project lead team, construction managers and workers should be trained on the importance and methods of preventing water intrusion. They should continually seek out ways to direct water away from the building during construction, such as installing temporary gutters and downspouts, if necessary.
Construction defects and workmanship problems may begin to manifest themselves during the first few post-construction months. Beyond the damage to the physical property, the safety and lives of the occupants could be at risk should a breach in the building envelope or faulty interior plumbing cause a rapid incursion of water.
To minimize the risk of water intrusion post-construction, contractors should consider providing instructions to property owners and managers on proper maintenance and operation of the structure. Be sure to also ask manufacturers to inspect installations for warranty purposes.
The most effective way to combat water intrusion at a construction site is to be proactive, taking measures prior to construction and during the building process to minimize water damage.
- Schedule construction around peak periods of expected rainfall
- Identify water sources and develop plans to control each one
- Consider hiring a hydrologist to evaluate the local water table
- Determine how to direct flow away from the structure using perimeter drains
- Create a daily inspection report to check for damage, leaks or intrusion
- Immediately alert architect/owner of design features that may allow water intrusion
- Develop the project schedule with completion of the building envelope prior to installation of finishes
- Schedule the completion of site drainage, paving and landscaping as early as possible
- Assign responsibility for daily inspection to specific personnel
- Inspect and test all water services (including fire sprinklers) and waste lines before closing up walls and installing ceilings and floors
- Ensure that certain temporary water lines, hoses and accessories are adequate and can handle the required pressure
- Ensure pressurized sprinkler head protection is in place, including temporary sprinkler head protectors, emergency sprinkler flow stoppers, warning signs and emergency collection barrels
- Check that temporary water sources are properly shut off when not in use
- Never rely on a hose for the containment of water pressure
- Properly install all building penetrations and check for leakage
- If needed, provide temporary coverings at any exterior openings
- Make certain all roof drains are installed as early as possible and regularly maintained
- Direct temporary and permanent roof drains and downspouts away from the structure
- Slope all grades away from foundation
- Inform the security services of higher-risk locations throughout the building
- Create an Emergency Tool Box that contains wet/dry vacuums, squeegees, mops, etc.
When Prevention Goes Amok
No matter how attentive a project team is, the unexpected may occur. Turner’s best practice for planning a response to water intrusion is to have necessary material easily accessible. Turner keeps emergency water kits in gondolas staged on floors where work is underway, Blackburn said. The response kit includes electrical cord, multihead GFCI, a wet/dry pump vacuum, puddle pump, role of poly, rubber boots, hose, squeegee, pipe wrench to close valves, broom, bucket and, in some kits, a fire sprinkler shut-off device.
Developing plans that are focused on discovering and addressing damage sooner rather than later is critical. The later the discovery of a water intrusion, the greater the impact on the construction schedule, and the greater the likelihood that repair costs will incur. Q
Lessons Learned #1:
Construction was substantially completed on a 122,000-square-foot, three-story building attached to a hospital. A clamp failure on a water supply line to some equipment resulted in a foot and a half of water covering 15,000 square feet of the first floor. The financial loss was $400,000, and the project completion was delayed by four months. What could have been done differently? An effective water intrusion strategy pre-construction would have included:
- A flow meter to notify a change in water usage
- A documented contractor installation inspection by a professional other than the installer
- Testing the water supply to the equipment after the installation
- Waiting to turn on water supply to unit until testing could be completed
- Hiring for after-hours inspection of the property, which would have reduced the amount of water flow from 12 hours to about four
Lessons Learned #2:
Two new buildings were under construction on a university campus by a general contractor who had a 20-plusyear relationship with the university. The project was designed to be LEED Silver Certified and designed with ISO Class 6-Fire Restrictive construction. A heavy spring rainstorm overwhelmed the sump pump that burned out shortly after the storm began. PVC piping was used as a temporary interior roof drain leader and was overwhelmed at various connections due to the high volume of water. In addition, a roof hatch was left ajar.
These envelope breaches resulted in two feet of water in the subgrade floors and sheetrock/drywall damage to the uppermost floors. The damage? $500,000.
Although no one can control Mother Nature’s fury, additional planning from this experienced contractor could have included:
- Securing roof hatch with the first threat of coming of severe weather
- Checking proper pitch, support and connections for temporary piping of roof drains
- Provide back-up pumps or design alternate drainage systems to allow water to be diverted from the building