Warehouse water leaks – from the neighbor?

The claimant sued the insured for causing mud and water damage to the claimant’s warehouse.   Specifically, the damage was allegedly caused by the insured’s recent construction activities at the insured’s adjacent warehouse.   GEI was assigned to investigate both sites and determine the cause and approximate age of the water intrusion of the claimant’s site.

Our expert inspected both buildings.   The insured’s building was a single story institutional office building, constructed in 1962, with an asphalt rear parking lot and a recent addition.  The claimant’s building was a tilt-up concrete building, constructed in 1979.

The claimant’s building included offices attached to an open plan warehouse, all with a concrete floor.  The building abutted the insured’s parking lot on the claimant’s east end of the building.

It was enclosed by tilt-up construction concrete panels and a roof of glued laminated beams and natural timber overlaid with roofing felt.   When inspected, there was mud and silt on the floor of the warehouse area.   There was efflorescence in the joints in the walls, between the panels.   There was also evidence of water penetration at the roof level, affecting the header timber to the east wall.  In addition, the joint between floor and wall showed an increased presence of efflorescence along the north side, (the wall most distant from the insured’s lot).

Efflorescence is the existence of salts of evaporation because of the movement of water, generally through a concrete, brick, or other semi-pervious material.   When those salts are present at a higher concentration, such as at a joint, it shows that the joint has had an excess of water flow through and around it resulting in a greater deposition rate and accumulation.

Dry joints between adjacent exterior wall panels are normally filled with a backer rod and sealed with a flexible sealant on both sides, usually limited to approximately three quarters of an inch width.   The joints in the claimant’s wall were approximately one and a quarter inches to nearly two inches wide and showed signs of failure. Where below ground conditions exist, precautions are normally taken to prevent water intrusion through the concrete wall and joints.   The claimant stated that he was present when a black coating was applied to the outside face of the wall panels, but that was over 30 years ago, so his memory was hazy.   The claimant’s interior floor slab level was approximately three feet lower than the insured’s parking lot level.

Expansion joints are normally used in a concrete floor slab to allow movement of the floor slab in response to thermal changes on either surface of the slab that will result in expansion or contraction of the concrete slab.   The placement of the standard expansion joint is such that an area not exceeding 400 square feet is the normal maximum slab size for a 6-inch thick slab.   A thicker slab will increase this normal maximum.  The expert assumed the floor slab to be at least 6 inches thick with greater thickness at the edges as a foundation support to the wall panels, given the warehouse use and assuming construction was in compliance with the building codes.   Good construction and engineering practice requires the installation of a moisture barrier beneath the slab where it may reasonably be expected that moisture will exist.   It is reasonable to expect that moisture will exist at lower grade levels on the down slope side of a development lot.   Expansion joints will also normally include sealants or a flexible waterstop to prevent the movement of water up through the slab.   There was no evidence of such fitting in place.   There was evidence of upwelling of water, silt, and salts of efflorescence at several locations within the slab through expansion joints and cracks unrelated to the purported intrusion of water from the insured’s parking lot.   There was no effective vapor barrier under the concrete floor slab.

The insured’s rear parking lot was paved with asphalt, with proper swales and drainage outlets for the removal of rainwater collected there.   Recorded rainfall events for the six months prior to the loss were taken from the closest reliable reporting station, a local airport.   The records showed that precipitation was lower than normal for that period than in previous years.

The insured’s building was built in 1962.   The claimant’s building was built in 1979.   The claimant’s site should have been protected by the claimant against water infiltration from the higher ground of the insured’s site.   According to the claimant’s statement, this appeared to be the case, that some protection was envisaged and put in place.   The insured’s site construction did not disturb or disrupt the water intrusion prevention system on the claimant’s building.   Further, such water intrusion prevention system should have been designed for the life of the building and maintained as such by the claimant.   It is evident that this water intrusion prevention system was not functioning, nor had it been functioning for some time, based on the efflorescence present on the walls, together with efflorescence coming up through the floor.   The presence of the efflorescence indicated a failure of the water intrusion prevention system for a period of several years.   Based on review of all available information, there was no evidence of action taken by the insured to disrupt or to render ineffective the claimant’s water intrusion prevention system.   The cause of the damages was the claimant’s failure to maintain the wall and floor water seals.

The age of the damages cause was approximately twelve months to five years.

A balcony collapse

We read an interesting article in the morning paper about a balcony collapse. Later on, we were assigned the investigation.

The insured’s property was a four-story condominium complex with an in-ground swimming pool at the first floor level.Walking up to the building, the fourth floor balcony was clearly visible.  While the walls of the balcony were still in place, the main body of the balcony floor had fallen down onto the floor of the third floor balcony, directly underneath.    Were one to step out onto the 4th floor balcony, one would have a quick trip, through the gaping hole with jagged edges, onto the third floor balcony.

The partially collapsed balcony floor was supported by three 6-inch deep I-beam section cantilever steel beams projecting from the building.   A 9.5-inch by 3-inch outer edge C-channel steel was bolted to the ends of the I-beams.  The middle I-beam (off-center from the balcony sides) appeared to have been embedded in the chimneystack, but the extreme side beams could not be discerned as to their point or method of attachment to the building, and may have been similarly cantilevered or may have been attached using a bolted mechanism.  A framed wall surround to the balcony sat on top of the outer edge C-channel steel and the side I-beams.  The wall was coated with stucco.  The floor of the balcony was formed using a 2-inch thick concrete slab poured integral with formed steel trough members approximately 1 – 2 mm thick, with those members spanning between the building and the channel edge beam.

The balcony floor concrete was reinforced with steel reinforcing bars (rebar) in the 2-inch thickness using ½-inch rebar.  Beneath the trough members, forming an enclosed space, was a further former layer of rebar, under and attached to which had been laid a steel wire mesh, to which the stucco ceiling surface below the balcony had been applied.  The rebar appeared to have spanned between the edge beam and the building in support of that mesh.  Drainage from the slab was taken through a 2-inch by 4-inch scupper to a rainwater hopper attached to the outside edge of the balcony and then to a down pipe.

The observed condition of the rebar, the trough members and the steel cantilever beams and edge beam was that of corroded steel.  The trough members appeared to have disintegrated and to be almost completely comprised now of rust, with the rebar and steel beams having an unknown lateral extent of corrosion, but directly observable as at least 1 mm depth of corrosion product to the rebar and light corrosion to the beams.  It was our expert’s opinion that such corrosion had taken at least five years to form in the confines of the enclosed floor space of the balcony structure.  What remained of the edges of the concrete floor of the balcony had no waterproofing finish to it.  The unit below the affected unit had suffered penetration of water from the balcony level above, as evidenced by staining and efflorescence around their chimneystack.

The balcony floor fell because the floor of the balcony had been exposed, without sufficient protection, to the elements of the weather, allowing penetration of the permeable concrete slab by accumulating rainwater.  The rainwater percolated through the concrete to the unprotected steel trough and rebar and caused corrosion to occur in that steel.   Once the trough and rebar were sufficiently corroded, they could no longer support the weight of the concrete floor.  The floor then fell to the balcony below it.  The direct cause of the failure was the lack of waterproofing on the surface of the concrete deck.