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.
Local jurisdictions dictate the safety regulations surrounding window washing methods - always confirm the requirements of your local authorities. Generally, windows in buildings 3 stories tall or lower can be washed using ground-based lifts or telescoping window washing poles. However, for buildings over 3 stories in height, it might make more sense to wash 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 Suspension 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.
The following photo shows a series of safety anchors on the roof of a building. These anchors are bolted through the concrete slab, but they can also be welded to steel beams below the slab prior to the concrete being placed. In this photo, the roof insulation and roofing membrane have not been installed.
Portable Outrigger Suspension System
To remove the load from the parapet wall, a transportable outrigger is used. The transportable 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, metal plates are used to counterweight the outrigger. The image below shows the primary suspension line attached to the outrigger and the secondary fall arrest (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.
The photo below shows a portable outrigger system on the roof of a building during construction. In this image, the outrigger is secured with a series of metal plate counter-weights.
Davit Suspension System
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. Davit arms customized for the building's specific conditions 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 arrest 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 the 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.