Unusual Problems: Problem #01

Problem #01:
The Moving Pipe,
which only leaked during strong wind.

Palo Alto Central Condominiums
153 California Avenue
Palo Alto CA USA
January, 1997

INSPECTION REPORT for Unit F101
(All jobsite directions such as left or right, are with the viewer facing the property from the street or in front of the front entrance.)

Unusual Problem 1

History

In a condominium Association, a unit named Unit F101 and adjacent units and storage spaces had a severe continuous water leak from the outside walls along the Northwest building exterior.
This leak had existed since construction was completed almost ten years previous.
Repeated and constant attempts by many different companies over several years failed to correct this problem.

Location

Unit F101 is on the ground level, above an underground-parking garage, at the West end of Building 153. There is a stairway attached to the exterior wall of F101 leading up to an exterior second level walkway with stucco-covered safety railing balustrade used as the main entrance for second story units. This walkway top surface is finished in 2-inch concrete over plywood decking and wood framing and stucco covers the sides and bottom. All walls of the buildings, stairways, walkways etc. are stuccoed.
Prior attempts to repair the leaks had included re-surfacing the stucco, replacing the aggregate stairway, re-surfacing the second level walkway etc.
The consensus of the many companies attempting to fix the leaking was that the problem was in the rain gutter-to-roof and/or the top wall flashing.

Incorrect repairs were requested

SimpCo was asked to correct improper flashing where the galvanized-steel rain gutter mounted against the stucco at roof level above the West corner of the Northwest exterior wall. A downspout existed at this corner, mounted upon the Northwest wall. The gutter had been improperly installed directly against the wall sheathing before the stucco was installed. When the stucco was installed, the installers ended the stucco below the rain gutter instead of installing stucco behind it. Additionally, the gutter installers failed to seat and solder the gutter outlet in a good competent manner and water readily escaped through the bottom of the gutter. Water escaping from this leaky outlet was allowed to run directly behind the stucco.

SimpCo initiated a Forensic Examination

SimpCo conducted a Forensic Examination of the outside and inside of the roof and walls of the top floor and the outside of all other floors. Although the poor workmanship problems listed above were evident, SimpCo staff knew that the amount of water leaking from this defective gutter outlet was grossly insufficient to cause the massive amounts of water entering into the condominium.

SimpCo changed the repair specifications and repaired the defect

Rather than proceed with the repairs, SimpCo staff opened several holes into the structure and the enclosed deck and stairway. SimpCo staff inserted cameras designed to fit through small apertures into these examination openings. On one test aperture into the walkway SimpCo staff discovered the entire cause of the leaking problem and subsequently repaired it. SimpCo staff also repaired the poor workmanship of the wall flashing and the defective rain gutter and downspout conductor head installation.

Explanation and drawing of the defect

The problem is shown in the attached drawing. The 3x4-inch commercial-size galvanized steel downspout at the West end of the Northwest wall led into a 3.25x4.25-inch galvanized steel nipple set into the concrete surface of the walkway, an unusual arrangement. This 12-inch nipple lead into a 4-inch round cast iron sewer pipe that led horizontally inside of the walkway until it could exit downward into the sewer lines fastened to the ceiling of the underground parking garage.

The defect

The nipple was 1-inch too short of joining the downspout to the sewer pipe. This 12-inch nipple should have been 14.5-inches long. The rain gutter downspout had no middle fasteners. When the wind blew hard, the downspout deflected slightly. This slight downspout movement caused the nipple, pivoted at the concrete walkway surface entrance, to swing its bottom end fully two-inches in the opposite direction. When the nipple was in a swung-over position, it was no longer over the sewer pipe opening and the 12-square inch volumetric area of exiting rainwater water was dumped into the walkway interior space. The water then filled the walkway like a bladder and soaked through the wall where the walkway was adjoined to the building and into the inside living quarters.

It only leaked when the wind blew hard

When there was no wind, all of the pipes hung plumb, then 99% of the water entered the sewer pipe and there was no leaking! However, when the wind blew during rain, the downspout shifted slightly causing the bottom of the nipple to move sideways thereby aiming its water egress into the open plenum of the staircase walkway.

Biography

Gene Simpson, an engineer with decades of construction experience, holds a Masters Certificate in Concrete Repair. Mr. Simpson will answer short questions regarding this article if you call him at SimpCo Corp., 650/ 289-0006 or email via the SimpCo.com Website. As the Technical Operations VP at SimpCo, Gene is in charge of Structural Forensic Analysis, concrete and post-tension member repairs, assisting the Project Management staff with technical specifications and similar tasks.

Last updated on 2nd June 2004.
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