Freequently 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.

How long can I expect my roof to last?

We can provide you with shingles rated to last 50 years.

Still have questions?

Contact the roof experts at Al’s Roofing Service at 920-497-1966 or request an estimate online. We’ll help you navigate the ins and outs of roofing to help you get the best roof for your needs.

We are Available 24/7!

If you have residential roofing needs or concerns, give Al's Roofing Service a call at (920) 497-1966 to get started with a FREE Estimate. You can also schedule a consultation by completing our contact form. Our expert team will respond quickly and professionally to address the issues.

Call Us Anytime: 920-497-1966