Black streaks on your roof: What North Alabama homeowners should know

Black streaks often mean algae is growing on your asphalt shingles. A roof with staining may still be in good condition and suitable for cleaning. Leaks, missing shingles, and storm damage need a roofer’s attention first.

For algae on asphalt shingles, the Asphalt Roofing Manufacturers Association rules out power washing and scrubbing with a brush or broom. The cleaning should follow the shingle manufacturer’s instructions.

What those black streaks usually are

Roof algae can leave brown or black discoloration across a slope. Shade and lingering moisture help explain why one side of a roof may look much darker than another.

The pattern is useful, but color alone does not identify the problem. Soot, leaf debris, moss, lichen, and previous repairs can also change a roof’s appearance. A photograph of the whole slope shows more than a close-up of one streak: the trees above it, the valleys where debris collects, and the direction the marks run.

Take that photo from the ground using your camera’s zoom. There is no need to get on the roof for a quote request.

Roof staining and roof condition

Discoloration and roof condition are separate questions. Cleaning can improve the appearance of suitable shingles, but it does not diagnose a leak or assess the decking, flashing, and ventilation beneath them.

If the roof looks intact and your concern is staining, ask about cleaning. If you have seen water indoors or noticed missing or broken shingles, start with a roofer.

Why asphalt shingles should not be pressure washed

Shingles have a layer of protective granules. Aggressive washing or scrubbing can remove them along with the visible growth. Bringing a pressure-washer nozzle closer to a dark patch adds force without addressing the cause of the stain.

That is why our low-pressure roof cleaning service uses a roof treatment instead of a high-pressure stream on the shingles.

How low-pressure roof cleaning works

We choose the treatment for the roofing material and growth, apply it at low pressure, and account for the gutters, siding, metal details, and landscaping below the roof. Shingle condition and where runoff will go affect how we carry out the work.

Before booking, you should know which roof sections are included, what change to expect, and whether any areas need a roofer’s attention. Those details also help you compare quotes for the same work.

How to handle moss and lichen

Raised moss or attached lichen needs a different assessment from a flat algae streak. Scraping it away can disturb the shingle surface. ARMA directs homeowners to the shingle manufacturer for moss-removal guidance.

Ask how attached growth will be handled and whether any will remain after treatment. Avoid assuming that every roof should look completely clear before the crew leaves.

What to look for from the ground

Useful details to share include:

• The slopes where you see streaks or raised growth
• Overhanging branches and debris collected in valleys
• Missing, lifted, curled, or broken shingles
• Recent storm damage or signs of a leak indoors
• Fences, planting beds, or other features that affect access

Marks on the outside of a gutter are a separate issue. Exterior gutter whitening cleans those visible faces. It does not remove debris from inside the gutter or clear downspouts.

When to call a roofer first

Leaks, damaged flashing, missing shingles, and an uneven-looking roof need repair advice before cosmetic cleaning. The same applies after a branch strike or storm that may have damaged the roof.

If you are unsure which service you need, describe the problem and share ground-level photos. We can discuss the cleaning request without treating it as a roof inspection.

Questions to ask a roof-cleaning contractor

Ask how the method follows the shingle manufacturer’s guidance, how nearby plants and finishes will be protected, and what results are realistic for the growth you have. Request current liability-coverage documentation if you need it for your records or HOA.

A clear answer should relate to your roof and the work in the quote.

After the roof is cleaned

Save the photos so you can compare the roof’s appearance later. Keep up with normal roof maintenance and have new damage or leaks checked promptly.

Algae can return. Cleaning improves the current discoloration, while shade, moisture, and debris continue to affect the roof over time.