Drip, Drip, Drip
A look at the inside of a cabinet can reveal whether water damage resulted from a one-time event or a chronic leak.
As the kitchen cabinet doors swung open, the familiar odor of dampness and mold hit like a wet gym sock. "That damage just happened," remarked the insured.
The particleboard cabinet base was sunken, and several fasteners had failed. The damage looked old, suggesting that it was a long-term leak—but how long? An adjuster faced with a water claim should be prepared to assess the cause of loss, which often can be judged based on damage to cabinet bases. A one-time burst pipe will leave different decay than a chronic leak.
The behavior of water released onto faced and unfaced cabinet bases is different, so the type of cabinet facing has to be considered in the assessment. Water discharged onto unfaced particleboard is absorbed with localized swelling. Water discharged onto faced particleboard migrates to adjacent walls depending on the pitch. Once moisture is absorbed and swells the exposed particleboard edge, a repeated water release will flow to areas of lower elevation of the base, and the consequential swelling will create a "bowl-like" appearance.
When water damage occurs inside a cabinet, it usually originates as a low-volume, intermittent leak from the drain or water supply. When kitchen and bath vanity damage is incurred, replacement costs can range from a hundred to a thousand dollars or more per linear foot, so there is an incentive to understand more precisely how cabinets respond to moisture.
In some cases, claimants inflate claims, listing cabinets that were damaged by a chronic, unrepaired leak as part of a covered, single event. Sometimes it's an honest mistake; stored contents can obscure a slow leak's effect on a cabinet base. Nevertheless, an adjuster is there to determine what damage occurred from the covered event and what didn't.
There are current testing procedures used to establish national cabinet performance standards; however, they test only modest moisture-exposure conditions. An "acceptable" performance requires that there be no visible delamination or swelling, and the finish should not discolor, blister, checker, whiten or show other film failure. Though this test procedure is practical, cabinets must be tested under more severe moisture exposure conditions to reveal the impact of low-volume, long-term plumbing leaks.
Two new experiments have been conducted to address conditions more applicable to insurance claims: the first on faced and unfaced cabinet bases and a second on faced, whole cabinets.
In the first experiment—which evaluated the physical response of three unfaced and three faced cabinet bases to repeated water exposure—one faced and one unfaced cabinet supported no weight; the two others in each category held five or 10 pounds, respectively, representing contents. The experimental cabinet bases were exposed to a simulated drainpipe leak that discharged 200 milliliters of water daily (a little more than half a can of soda) onto the middle of the cabinet base. The cabinets were constructed identically using commercially available cabinet screw fasteners to attach the cabinet walls and kick plate to the base. (Photograph 1)
The discharge tube dispensed one drop every four to six seconds over the course of 90 to 120 minutes until empty. Plastic sheeting was placed under each cabinet base and stapled to the kick plates to prevent water from dripping onto the cabinet bases below. Measurements of moisture content (using a Tramex non-penetrating Moisture Encounter Plus), dimensional changes (using a Westward Micrometer, Model No. 1AAU4), and base drop in millimeters were obtained 35 times during the 91-day experiment. Two Model U10 Hobo data loggers by Onset Computer Company were placed inside the enclosed cart to monitor humidity and temperature. The first set of cabinet bases was made with 5/8-inch, unfaced particleboard; the second set was made from 5/8-inch Limonene-faced particleboard.
Measurements at multiple locations on and around the cabinet base catalogued changes in thickness and moisture content. An aluminum bar measuring 34 inches long and ¾ inch wide was placed across the cabinet base to measure downward deflection.
Observations in Experiment One
The largest decline occurred in the unfaced particleboard, with the 10-lb. weighted base collapsing after 64 days. (Figure 1 and Photograph 2) The control base and the base that supported a 5-lb. weight deflected downward more slowly and did not collapse in 88 days.
The faced particleboard bases responded similarly whether they supported weight or not. (Figure 2) The cabinet base that supported the 5-lb. weight declined faster than the base with 10 pounds. After 88 days, the faced particleboard base that supported the 10-lb. weight formed a shallow bowl. (Photograph 3)
The dimensional change (swelling) reported for the unfaced particleboard was 40% (average of all measurements) from the initial to the final day. The average dimensional change of the faced particleboard was 45%. The response of the unfaced particleboard was uniform because water added to the cabinet base was quickly absorbed in the middle of the base and distributed via capillary action. The faced (non-permeable) particleboard had a non-uniform response because the direction of water movement depended on the slightest pitch of the cabinet base. During the first few days of the experiment, water flowed across the cabinet base surface to a side or back wall. Once water penetrated the wall joint, the particleboard swelled and directed free water to another area of the base. After one month, several base sides were swollen, and free water was retained in the middle, simulating a "bowl-like" effect.
The entire unfaced particleboard cabinet base achieved saturation (>30%) after 35 days. Moisture absorption by the faced particleboard cabinet base was variable because the faced materials were not penetrated. The moisture content in the faced cabinet base and walls varied because water flow direction responded to gradual changes in cabinet base slope. As a result, fasteners located along some sides of the cabinet base were exposed to water for longer periods of time than others. This condition contributed to some bases exhibiting fewer declines than others despite supporting more weight.
Temperature measurements fluctuated between 64° F and 84° F; average daily relative humidity measurements were in excess of 80% RH during the study period. Temperature and relative humidity fluctuations were influenced by the daily addition of water and the periodic removal of the plastic sheeting for photography.
Other Observable Phenomena
In the first experiment, all of the unfaced particleboard bases supported prolific microbial growth after Day 11. The extent to which microbial growth weakened the unfaced particleboard is unknown; however, previous experiments with unfaced particleboard documented swelling of up to 22% within 30 days when exposed to constant moisture (Moon and Price, 2009). During the first 30 days of moisture exposure, swelling rather than microbial growth has the primary impact on particleboard strength. Once the particleboard becomes fully saturated, microbial oxidation imposes an increasing stress on board strength.
Some types of water damage often seen in the field were not observed in this experiment. In Experiment 2, among the unfinished, unfaced oak components, no cracking or joint separation was observed. This damage is consistent with moisture exposure followed by rapid drying efforts that can cause joint separation and cracking because the wood experiences both swelling and contraction during drying.
Fasteners are critical to the structural integrity of a cabinet. In a technical study, seven types of cabinet fastening methods (Lamello, dowel, blind dado, nailing strip, KD fastener, pocket screw, and staple) were tested for shear, tensile and parallel shear strength under dry conditions. The study revealed the poor performance of KD fasteners, pocket screws, pre-glued dowels, and staples. The fasteners used in Experiment 1 were screws, while staples were used in Experiment 2. Fastener test results suggest that if a particleboard cabinet is constructed with dowel and glue or Lamello fasteners (tested to be stronger), the progressive decline in cabinet base height may be substantially more.
Testing Whole, Faced Cabinets
The objective of the second experiment was to evaluate the rate of cabinet base decline of commercially available faced cabinets exposed to repeated moisture under conditions of elevated humidity and a 10-lb. weight.
Three sink-base kitchen cabinets (Continental Cabinets, 36" wide, sink-base) were purchased. The first cabinet was used as a control and exposed to test conditions of 75o F and 55% relative humidity. The second cabinet was exposed to elevated humidity using a fish tank aerator placed inside a container of water suspended in the cabinet. The third cabinet was exposed to elevated humidity, daily watering (200 ml) from the device described above, and a 10-lb. weight. A Hobo data logger was placed inside each cabinet to monitor relative humidity and temperature for 152 days. All cabinets were enclosed in plastic sheeting. (Photograph 4.)
Both non-penetrating and penetrating moisture meters (Tramex Moisture Encounter and Moisture Pro) were used to obtain percentage moisture content from 33 locations along the left side interior/exterior, front toe kick (particleboard), front face (solid oak) and interior base (faced particleboard). Dimensional measurements were obtained at three locations along the left and right side panels and the center of the front face. The cabinet base was not measured. Measurements of cabinet base downward deflection were conducted as described above. Measurements of pH (using Merck pH paper strip) were obtained for the first 100 days to see if solutes extracted from wood extracts or biological activity changed the pH.
The control cabinet and control cabinet with high humidity experienced no change in base height. (Figure 3) The test cabinet base gradually declined 34 mm after 152 days, and the base supported a pool of water. (Photograph 5) This is characteristic of plumbing leaks that occur inside faced particleboard cabinets. (Photograph 6) Water accumulated on the impervious Limonene coating as was observed during the first experiment. The cabinet bases exposed to ambient conditions or ambient conditions plus elevated humidity showed essentially no decline following months of exposure to elevated humidity (>80%).
Among the three dimensional measurements (left and right side panels and front face) obtained from the three cabinets, an average change of approximately 1% was measured throughout the duration of the experiment. Dimensional measurements were not obtained from the cabinet base materials.
A comparison between the initial and final moisture content revealed an average increase of 0.81% in the control cabinet (initial 9.05%, final 9.85%). The cabinet exposed to elevated humidity revealed an average increase of 3.9% (initial 9.6%, final 13.48%). The test cabinet (daily water, elevated humidity and 10-lb. weight) revealed an average increase of 6.1% (initial 9.5%, final 15.6%). Measurements of pH obtained from water discharged into the cabinet and water that accumulated in the cabinet base reported slightly alkaline measurements of 8.0 pH units throughout the entire test period.
Temperature and relative humidity measurements in the ambient control cabinet fluctuated between 70° F and 84° F with average daily relative humidity above 80% RH. The humidity control cabinet fluctuated between 70° F and 85° F and ranged 73% to 85% RH. The watered and humidified cabinet fluctuated between 72° F and 88° F and 60% to 88% RH.
These two long-term tests conducted on faced and unfaced particleboard cabinet bases under different environmental conditions revealed that a minimum of 64 days is required for an unfaced cabinet base to collapse following daily exposure to a low-volume water leak (200 milliliters). Cabinet bases constructed with faced particleboard and exposed to daily moisture releases did not collapse following tests conducted for 88 and 152 days; although, they did droop.
When confronted with a water damage claim, take a look at the cabinet bases and determine if losses were caused over a long duration.
Wet Cabinet Facts
- Faced and unfaced particleboard cabinets withstand interior, low-flow plumbing leaks for several months more before collapsing.
- Faced particleboard is more resistant to water damage than unfaced particleboard.
- When a leak occurs inside a faced particleboard cabinet, the water initially flows downhill to a joint; unfaced particleboard absorbs the moisture and prevents flow.
- High humidity (>90%) alone does not cause a faced interior cabinet base to sag after 150 days.
Brett Davis is a Certified Residential Contractor, Master Window Installer and a Building Scientist with HSA Engineers & Scientists. Don Rondy is a Certified Indoor Air Quality Professional, Florida Certified Mold Assessor and Building Scientist with HSA. Dr. Ralph Moon (firstname.lastname@example.org) is director of Building Sciences at HSA Engineers & Scientists.
The authors would like to thank the following colleagues for their editorial comments and technical assistance: Nicholas Albergo, P.E., DEE, Chin S. Yang, Ph.D., Bruce Bosserman, P.E., Robert Braun, P.E., Jeff Wilemon.