All exterior low slope or flat roofing membranes get grimey over the life of the roofing system from airborne pollutants and dirt.
The buildup of dirt on a darker shaded roofing surface is less noticeable than on a light colored or white membrane. The type and amount of grime accumulation is usually related to the location of the installed roof system. Each type of “dirt” requires a slightly different approach and level of effort to clean a roof surface.
Some of the 1st and second generation of flat roof houses and other buildings now need roof maintenance due to water accumulation in some roof areas. Also think about many of the original roof materials installed on these roofs have reached the end of their useful life.
When repairing, the owner must keep in mind that flat roofs are extremely sensitive to human traffic.
There are two main issues when a lightly colored roof system becomes dirty:
1. Aesthetically, a clean roof looks better and helps with curb appeal and property values.
2. Practically, a clean roof will be more energy efficient.
With current design initiatives, an increasing number or designers are looking at environmentally friendly roofing designs to lessen energy expenses which save natural resources. Other considerations in dense areas is to lessen the effects that commercial roofs have on heat islands.
Low slope and flat roofing membrane manufacturers exclude appearance from warranties as an uncontrollable variable. If the building owner wishes to clean his roof to restore the reflectivity or good appearance of the membrane, a materials list and directions for DIY cleaning a warranted roofing system are below.
It is the building owner’s responsibility to become familiar with and adhere to local and regional codes and laws with regards to approved cleaning soaps and proper disposal of cleaning water.
If you are not comfortable working at heights, it is advised to hire a professional roof cleaning company.
Needed equipment: soft bristle brooms, mops, and squeegees.
1. Broom clean the roof surface. This will remove loose dirt and debris that may clog the drains or abrade the membrane surface during washing.
2. Wet the roof surface and allow to soak in for five minutes to soften any dried dirt.
3. Dislodge the dirt from the flat membrane surface by sweeping the wet surface with a soft bristle broom.
4. Thoroughly rinse the area of membrane being worked on to determine the effectiveness of cleaning with just water.
5. If there is still dirt on the roof membrane, re-wet the roof surface and allow to soak for 5 minutes.
6. When soaking, apply a generous amount of Spic and Span® or tri-sodium phosphate to the wetted membrane.
7. Scrub the membrane again with the soft bristle broom.
8. Thoroughly rinse with fresh water before the soap residue has a chance to dry on the roof membrane.
9. The steps above will get rid of most forms of dirt. If one cleaning does not get rid of the dirt, you may need to repeat steps 1-8.
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Cautions and Warnings:
Damage to the roof during washing operations is not covered under the warranty. If damage occurs during washing, it is the responsibility of the owner to repair.
Source for the following: genflex.com/wp-content/uploads/2013/04/Design-Criteria1.pdf
Do not abrade the surface of the roof membrane. Seams are typically laid shingle fashion towards the roof drain or gutter. Do not agitate, power wash or scrub against the seam. Go over the top or parallel to it.
A commercial roofing system is a major investment for a property owner. It is important to protect the roof system from accidental damage during cleaning.
Before hiring the project out to a local contractor, there are a few things to consider.
1. Building owner assumes all risk for damage to the roofing membrane during the cleaning process. Use extreme caution in performing the work yourself or hiring the job out.
2. The roofing manufacturer is available for assistance in writing the scope of work.
3. Many installers also offer roof cleaning services.
4. Perform a visual inspection of the roof system before and after cleaning the roofing membrane to identify any pre-existing roof damage and to verify the effectiveness of the cleaning process. It may prove beneficial to take photographs of the roof system before cleaning begins.
5. Do not use, or allow anyone else to use, a floor scrubber on the membrane.
6. Pressure washing equipment can severely damage a roofing membrane if not used by a professional with membrane roof cleaning experience. If a pressure washer is used in cleaning the roofing membrane, please keep the following items in mind:
a. Do not use any pressure washer tip less than a 30° arc. Tips with a concentration angle smaller than 30° will damage the roofing membrane.
b. Do not use a rotating tip apparatus.
c. Maintain a minimum of 24” (60 cm) between the pressure washer nozzle tip and the roofing membrane.
d. Do not use a pressure washer rated higher than 2500 psi (17 MPa).
7. Always get current certificates of liability insurance from the contractor performing the work with your company listed as an additional insured party.
8. If you suspect the warranted roof system may have been damaged during the cleaning process, contact the manufacturer immediately.
