El Segundo High School
El Segundo, Los Angeles, California
Repair and Restoration of Brick and Cast Stone Window Surrounds Over Rusted Steel Structural Elements
The brick and cast stone facade had suffered from long-term exposure to salt-laden air, with rusting and deterioration of internal steel components, causing damage to the masonry facade.
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El Segundo H.S. served as the setting for a famous scene with James Dean in "Rebel Without a Cause" but had endured some damage in the intervening years. |
The first overt evidence of a larger problem was this failure of brick veneer adjacent to one of the second floor windows on the west elevation(facing the Pacific Ocean, a quarter-mile away). |
A complete section of vertical brick window jamb trim had fallen to the ground, with obvious risks posed to any pedestrians below. |
The Main Administration Building dated from the original campus development of 1923 and the construction technology used was consistent with the period. Long mild steel I-Beams spanned the distance between window jambs and carried the load. |
When we were called to the site, we started with a thorough examination of all windows utilizing this construction technique. We noticed that most of the brick window headers displayed some evidence of displacement, a sure sign of an internal decay mechanism of some kind. |
Once the pattern became obvious, we noticed other signs of a pattern, including cracking along horizontal joints, yet more mute testimony to some internal process of movement. |
In some cases the internal stress relief was telegraphed through the brick itself, but always consistent with location relative to the same type of rectangular window. |
As the decay pattern emerged in ever more clear detail, we could discern that internal mild steel reinforcing elements were responsible, in this case forcing the pointing mortar out of the joints, due to internal expansive pressure. |
It should be noted that the rough, granular surface of the bricks is consistent with a masonry surface that has been sandblasted (cleaned with a silica-based abrasive medium under high pneumatic pressure) and the resulting open-pored surface rendered much more susceptible to the absorption of moisture - in this case, the salt-rich moisture of a Southern California marine environment. |
Mild steel in such an environment decays much more quickly than if it is protected (coated) to resist the constant onslaught of moisture containing such a salt-based chemical acclerant. This building was subjected to the same forces inflicted upon concrete roadways and cars in the Eastern U.S., where salt is routinely spread upon roadways to raise the melting point of ice. Anyone who has driven an East Coast car out West and tried to sell it at Bluebook pricing will understand how quickly such things progess, and how extensive the damage to the car's steel underside and frame can be. |
The decay process is know as Ironjacking and involves the expansion and decay of the iron (in this case steel angle and I-beams) as it goes through the oxidation process. |
Window utilizing the horizontal steel support system were in varying stages of decay, but all exhibited some evidence of the process. |
Cast stone decorative trim at the windows on both floors displayed evidence of the same decay mechanism in place ( in this case caused not by steel I-beams but by steel reinforcing bar placed internally along the axis of the precast decorative unit). |
Preparation of these damaged areas included the removal of all loose and unstable original material. |
Iron jacking and delamination ocurred on numerous decorative cast stone and brick areas around the facade |
In some locations, damage was minimal and only just begun; in others, the cracks and dislocation were advanced enough to pinpoint internal decay with accuracy. |
As with many masonry facades of this period, the cracks were only indicators that more hand-on investigation was needed. |
Usually, these areas can be fully exposed with a little prying, using fingers and a screwdriver. The underlying problem is almost always the original steel reinforcing. |
Preparation of brick damage is similar to methods used for the intitial repair of cast stone. Damaged or cracked units are carefully removed without damaging adjacent sound material. |
Repairs at the cast stone portions of the facade included the exposure of internal rusted iron, and after removal of rust using wire brushes, application of a corrosion-resistant coating to inhibit future rusting. |
Final repairs of cast stone surfaces included the application of a 'rendering' surface mortar, a thin coating of a cementitious mortar to completely cover the old deteriorated cast stone surface and yield a moisture-repellant surface for greater long-term durability. |
Typical construction detailing for this building included the use of red 'common' bricks to fill the void of the beam's 'web' area. A long piece of flat steel plate was welded to the bottom flange of the I-beam to support the decorative brick facade. |
Many of the window steel components were degraded enough that whole delaminated layers could be pulled out with little effort. Note the striated appearance of the steel as it delaminates. |
Initial treatment included the careful selective removal of all bricks in the area of steel decay. We always work carefully to minimize the damage or loss of original historic fabric. |
The next step in treatment focused on the removal of all unsound material, followed by grinding and wirebrushing to get the surface back to undamaged steel. |
Once the surface was back to sound condition, the entire exposed steel beam was coated with and epoxy-based anti-corrosion treatment to cover the steel and reduce or eliminate exposure to future moisture sources. |
New hot-dipped galvanized steel angle could then be attached to the original beam to provide a new support that would not be as easily reached by rain and seepage, and better protected against corrosion if it were. |
After placement of protective screens to avoid damage to the glass windows below, the new steel angles were welded along their entire length. |
Both Plug welding and Edge welding techniques were used, and the welds then coated with a cold-galvanizing compound to ensure maximum protection against future oxidation and decay. |
The bottom flange of the original support has been cut back to sound material, and the new angle will provide the support for the decorative brick facade. |
Salvaged bricks were then reinstalled in a full bed of mortar, and the outer joints cut back to receive the final application of pointing mortar formulated to match the adjacent original mortar. |
The finished repair area with a bonus of new flashing at the bottom of each window header to direct rainfall away from the window area. |
The entire facade was then cleaned with water only and treated to a saturating application of a penetrating water repellant to help this community asset to live to help educate another generation and more. |