Blog » Why is my Roof Appearing Discolored?

Staining is a common problem on roofs that are not properly cleaned and maintained. If you notice staining on your roof, itís important to have a professional roofing company take a look to identify the source, and formulate a plan to prevent further staining.

Distinguishing why roof stains occur and how to treat them is important for the value and safety of your home.  

A clean home exterior, including roof and shingles, is a determining factor in curb appeal.  Regular maintenance, like cleaning and sealing, is recommended to preserve the appearance and health of a roof.  Staining is a common problem on roofs that are not properly cleaned and maintained.   If you notice staining on your roof, it’s important to have a professional roofing company take a look to identify the source, and formulate a plan to prevent further staining.

Black or dark green streaking on shingles is most likely caused by algae that prefer warm, humid environments.  This type of algae in particular thrives on the moisture and shade provided by certain roof pitches. These unsightly streaks are oftentimes located on north-facing roof slopes due to lack of direct sunlight.  A chemical can be applied to rid shingles of stains, but it’s only a temporary solution and staining may reappear.  

Dark red or reddish brown stains are usually a product of rust.  Roof shingles located around flashings, chimneys, antenna mounts and other roof metals are highly susceptible to rust.  It’s important to ensure the chimney is sealed properly so that rust doesn’t leak inside.  If upon inspection the chimney is fine, it’s likely a problem controlled with regular maintenance.  The easiest way to keep the shingles rust-free is to regularly hose off the roof and apply sealants containing oxalic acid.  

Black stains around chimneys are caused by creosote from fireplace flues washing down onto the roof.  These stains are typically located below and in line with the chimney.  Dark black stains can also be caused by extractive bleeding.  This is a matter of shingle composition.  Shingles finished or primed with certain chemicals may produce a black pigment that seeps into the roof and runs or bleeds down.   It is not recommended to clean and remove these stains as it could cause further deterioration of the shingles.  

Although many of these stains are cosmetic and superficial, they affect the integrity of your roof, as well as your entire home.  Working on a roof is challenging, when adding chemicals and sealants to the job it becomes dangerous.  It’s always recommended to contact a roofing contractor to handle stain identification and repair work.  Contact PRS Roofing & Siding to schedule a free estimate today.