Canadian Underwriter

Water: The Structural Enemy

January 31, 2015   by Randy Henderson|Randy Henderson

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Water damage claims related to structures and building contents are not limited to catastrophic weather events, but are and ongoing source of property loss claims. Generally, losses can be divided into external and internal sources.

External Sources

This type of damage arises because water has been able to penetrate the building envelope over time or as a result of a short-term catastrophic event such as a torrential downpour. What is the building envelope? The physical components of the building envelope include the;

• Foundation system (below grade);

• Exterior wall system (above grade), including doors & windows;

• Roof system

Foundation System Breaches

Sewer Back-Up

The source of water infiltration in this type of claim is usually rather obvious but the cause might not be. A sewer back-up is often triggered by a heavy rain. In cases where a backflow valve has been installed, damage can still occur in the case of failure of the valve due to improper installation or manufacturing defect. For sump pump failures, a cause investigation includes looking at the installation, power source for the pump, and volume specifications.

Foundation Leakage

Causes of water infiltration through the foundation are often the result of improperly installed or degraded weeping tile systems and grading or landscaping that channels water toward the perimeter of a house rather than away from it. In some cases, intrusions into the foundation structure such as the installation of a deck or the roots from trees that have been planted too close to the home allow moisture penetration. A heavy rain or spring thaw are not the only sources of water in foundation leakage claims. Additional sources can include leaking in-ground pools, above-ground pools that burst and faulty exterior piping.

Window wells that have been installed without their own drainage system or where a lack of maintenance has allowed the drainage to become blocked can cause water to leak through the basement windows.

Water Infiltration Through Exterior Walls

The exterior cladding system’s purpose is to maintain a dry and stable interior space above grade. Systems are designed so that if moisture gets behind the facing such as the layer of bricks, it can be removed from the system by air circulation and drainage or weeping holes. While penetration from wind-driven rain is the most likely type of breach, a breach can be caused in conjunction with a faulty roof system or through an activity as innocent as watering a lawn or garden where the sprinkler is soaking the external wall as well as the grass.

Symptoms of a cladding system failure include;

• damage to the floor at the base of a wall such as water stains or cupping of hardwood floors;

• damage to interior window framing such as wood rot;

• damage to wall or ceiling finish including bubbling paint or stains;

• mould.

Typical causes of water infiltration include:

• cavity wall drainage system blocked or lacking weep holes;

• open Joints in wall system;

• breached Integrity of air barrier system ;

• improperly installed flashing at window and wall terminations;

• window caulking – missing or deteriorated.

Roofing Systems

The purpose of the roofing system is much the same as the exterior wall system; preventing penetration of the building envelope by weather elements. Roofing systems take an incredible beating from a combination of wind, rain, snow, ice and the sun. The materials employed in the system are of prime importance but as with all structural systems, the installation of the materials is equally important and in roofing systems, ventilation is a critical component. Regardless of how well the roofing system has been installed, over time, weather will cause parts of the system to break down. Poor flashing around vents, poor seals around skylights, missing shingles or other roofing material can all allow water to penetrate the structure.

Symptoms of a possible roofing system failure include:

• staining to ceiling finish (pot lights, ceiling, wall);

• direct water entry during a rain event;

• condensation forming in attics causing water damage;

• ice damming conditions.

In Canada, it is common to see ice damming conditions which create a build-up of ice and snow at the overhang. This is often caused by a combination of factors such as lack of adequate ventilation in the attic including soffit ventilation that is blocked by insulation and heat loss through inadequate insulation or sealing of access points such as the entry to the attic. Melt water enters the attic area and follows the path of least resistance, ultimately damaging ceilings, walls and floor finishes.

Internal Sources

As with damage from external sources, damage from internal sources can be sudden or occur over time. When water damage originates from an internal source, it is usually a result of damage, improper installation, improper use or lack of maintenance, but can also be caused by poor product design. Internal sources can be categorized as follows:

• fixtures (toilets, showers, fountains and taps or faucets);

• appliances (fridges, dish & clothes washers, water heaters,

hot tubs and aquariums);

• mechanical systems (piping & plumbing);

• condensation.


Failure of fixtures (faucets, taps, toilets, sinks, showers, fountains) can be dramatic where there is a substantial volume of water in the fixture or the break occurs where water is under pressure. A failure can arise from impact to the fixture such as dropping something heavy into a toilet bowl or sink. It can happen as a result of wear and tear as happens with rubber and plastic washers and bushings or can be the result of incorrect installation of the fixture or product defect.


Modern residences contain appliances such as refrigerators, water coolers, water heaters, boilers, dishwashers and clothes washers that can be the source of water damage claims. As with fixtures, failure of these items can arise from one or a combination of: sudden impact to the appliance, incorrect installation including restricting proper flow or not securing hoses, incorrect use of the appliance, or a manufacturing defect.

Mechanical (piping & plumbing) Systems

Homes have a remarkably complex network of pipes and valves to transport water throughout the structure and ultimately to the sewer system. These networks can fail as a result of weather conditions, improper installation, damage during renovations or a lack of maintenance over time. Winter weather conditions are a common source of failure. In a quest to save money, homeowners may lower or turn off heating systems when they are on vacation and in unique cases such as the ice storms in southern Ontario in December of 2013, power can be interrupted leaving a home without its heating source. If the temperature inside the house drops enough, water in pipes can freeze and burst the pipes. When the home warms up, the ice melts and water leaks through cracks in the pipes causing damage. Wild temperature fluctuations cause stress on joints which can, over time, cause a failure. As more homeowners finish their basements, the network of pipes becomes hidden, thus making discovery and cause analysis more difficult and costlier than ever.


Structural water damage can lead to large and complex claims. When it does, a proper investigation of how and why the damage was caused can speed resolution of the claim. If the cause of the damage arose from renovation or landscaping work performed by a third-party or from a manufacturing defect, subrogation may be an option.

Randy Henderson, B
. Tech, MBA, is responsible for client management at Arcon Forensic Engineers and regularly participates in fire, structural and mechanical investigations as a keen observer.