Frequently Asked Questions
Why are there streaks on my roof?
Streaks or Discoloration on Roof
Approximately five years after installation roofs can begin to show signs of dark streaks. The dark streaks usually appear on the north-facing slope of the roof and are mistaken for dirt or granule loss. These streaks are commonly caused by algae growth that is prominent in areas of the roof that receive less sunlight.
Moisture & Algae
Roof slopes that are shaded or receive little sunlight will hold moisture for a longer period of time which can result in algae growth. The discoloration or streaking is an aesthetic concern and does not affect the life of the roof system or its waterproofing characteristics.
Zinc strips can be added to a ridge of a roof to prevent algae from forming. Various solutions can be used to remove algae growth, although this is a temporary solution, as it will grow back.
Use Caution When Cleaning
It is important to use extreme care when attempting to remove discoloration as many harsh treatments or power washing can harm your roof system and result in granule loss.
Can a new roof be installed over old shingles?
New Roof on Top of Old Shingles
You should never install new shingles over the old shingle roof system.
Your roof system will not be eligible for a warranty if you do not remove the existing shingle roof system before installing the new system. Installing over the old shingles can also cause unusual shapes to form in your new roof system and the roof system will not look smooth and level.
Rot, Moisture, and Accelerated Roof Aging
If the old roof system is not removed it will not be possible to inspect the plywood deck sheathing for rot or deterioration that can become a much larger problem in the future. Moisture from the previous roof system can be trapped under the new system and the increased surface temperatures from having two layers of shingles can accelerate roof aging.