Window Washing -- Suspension Support
Discussion of window washing support and equipment is covered in two separate articles. This article covers the primary suspension support systems including davits, outrigger beams, and direct anchorage to safety anchors. The second article covers different kinds of window washing suspension platforms and seats.
Generally, windows in buildings 3 stories tall or lower can be washed using ground-based lifts. However, for buildings over 3 stories in height, economics dictate washing the windows from a roof-based suspension system where the window washing crew is lowered from the roof. This article covers the basic suspension support systems for use with flat roofs; however, there are more complex systems based on these that can provide support from sloped roofs or other complex situations make the solutions below problematic. For these types of complex window washing problems, we suggest working directly with a window washing equipment manufacturer or consultant.
Direct to Anchor System
The most basic equipment for window washing and safety anchoring is the safety anchor or tieback. In this case, permanent anchors are secured to the building structure. The graphic below shows both roof mounted anchors and wall mounted anchors. The window washers then tie their safety lines to the permanent anchors and pass them over the parapet wall. A structural engineer must design the anchoring system and the parapet to carry the loads created by the lines and the window washer.
Portable Outrigger System
To remove the load from the parapet wall, a portable outrigger is used. The portable outrigger is a beam with wheels that secures to a safety anchor. The beam is adjustable and extends over the top of the parapet and the primary suspension line secures to the beam. In addition to securing the outrigger to the permanent safety anchors, ballast (sand bags, weight plates, etc) may be added to the outrigger to provide more security. The image below shows the primary suspension line attached to the outrigger and the secondary fall suppression (emergency) line tied to a safety anchor. While this may be acceptable, using two outriggers is preferred to prevent any accidental load from damaging the parapet.
Another system for suspension of window washing equipment is the davit system. Davit bases are permanently attached to the building structure at a predetermined spacing. The window washing crew provides davit arms that are secured to the davit base. Lines are suspended from the davit arm. The davit arms are generally swiveling, which allows washers to set up all equipment on the rooftop and then swing out over the parapet wall. Fall suppression lines are also used with this system, but have been removed from the graphic below for clarity.
For buildings with high parapet walls, varying setbacks, or other complex forms, a roofcar system provides to greatest flexibility. The roofcar arm allows for a greater extension that other systems and can adjust without much setup time. The roofcar runs on rails or concrete pads and remains on the roof permanently. The single roofcar arm suspends both ends of the window washing staging.
2004 CSI Masterspec Division
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