Window cleaning isn't as easy as it sounds, especially on commercial buildings. You may have large, high windows, a glass covered high-rise, or challenging coatings on the glass. Commercial window cleaning services can handle all the washing needs, but you need to make sure to hire the best one.
Experience is the most important factor, particularly if you have a high rise building or another building design with challenging windows to clean. The window cleaning firm should be able to provide you with references to past clients, particularly those that have similar building styles. If the company is newer, then they should be able to provide references to the past companies that their cleaners worked for so that you can check on the individuals experience level.
You do not want to be liable if a window cleaner is injured on the job through no fault of your own. Injuries, while not common, can occur because cleaners are often working on dangerous or unsteady scaffolding, lifts, and ladders. Verify the insurance and any licensing requirements for your area have been met, and that all employees and their equipment is covered by the policy and licenses.
Some services use employees, while others bring in day laborers. In general, a service that fully employees their window cleaners is preferred, as they are more likely to be properly trained and to have the necessary experience to properly wash the windows. This is especially true if you have a high rise building or a situation where window washing is more challenging and requires greater skill. If the service does use independent contractors, they must be able to verify the experience level of the contractors.
A good window cleaning service will provide all of their own equipment — they won't expect nor ask to use ladders, squeegees, or cleaning fluids from your maintenance closet. The equipment should be in good condition and properly installed, and it must include necessary safety equipment such as harnesses and head protection.
Look for window cleaning companies that provide some sort of a guarantee on their work. A company with no guarantees doesn't stand behind their work, which means you may end up with streaks on the glass, or worse, damages. Most quality cleaners will provide some sort of a guarantee because they want your repeat business.
Contact a commercial window cleaning service if you want high-rise window cleaning done on your building.