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Why Do Roofs Stain?

Stains on roofs have a variety of causes, but noticing the stain colour, its location, in relation to the cause is a very vital issue.

Roof stains are a common issue that homeowners encounter in the course of their properties life. Do not be alarmed since many roof stains are not a cause for concern. Some stains can be a warning that your roof has an underlying damage, while others are just a blemish on your roof that can be resolved easily. However, you should be able to identify the kind of roof stains you are observing so you can contact the appropriate company or contractor for assistance either to clean, repair or replace.

Algae or lichen and moss can leave unsightly stains that do not only decrease the curb appeal of your roof, but also compromises the security of your home if left untreated.

Dark black or brown roof shingle stains are often caused by black algae, bleed-through or extractive bleeding of asphalt, dirt, soot or organic debris. There are also other roof stain colours and causes. Below are the major causes of roof stains on the building.

Algae

Some roof shingles that show blue, green, or dark stains indicate the presence of growing organisms, such as algae or moss. A species of algae called gloeocapsa magma is responsible for the green or black stains on your roof. It takes shape in streaks or patches of slime, a moist and slippery substance that can appear anywhere from blue, green to solid black colour. The presence of excessive moisture and sunlight makes for an ideal harvesting area for such microorganisms. While this type of algae is not harmful to your roof, it causes blemishes that can tarnish the appearance of your roof. Unlike mould and mildew, algae do not endanger your home or the health of the residents. Algae spores are airborne. They are spread through wind, animal and dust from neighbours that their roofs have been affected by the same issue. However, these microorganisms can lock in unwanted dampness or invite other, larger creatures that can cause havoc on the roofing structure. This will make an urgent problem which needs to be solved as soon as possible before it goes out of hand.

Treatment

To treat this stain, it is recommended to use oxygen bleach or a trisodium phosphate solution with a low pressure wash. Power spraying or scrubbing the stains on your own is possible, but may likely cause further irreparable damage. It is one of the best ideas to have a professional roof cleaning service to take care of this problem for you.

Prevention

To prevent algae from forming and spreading on your roof, it is advisable to add some sheets of copper or zinc to the peak points on the roof right above the discoloured areas. This is because algae is repelled by the presence of minerals of copper and zinc. During a slight rainfall, the water washes the metallic atoms over the roof and allows them to trickle down below, killing and preventing the formation of algae without anyone having to do any work.

Lichen

These are usually white or green in colour, but can come in brown or yellow colours as well. Lichen are a mixture of fungus and green algae. Lichen attaches its roots to the roof shingles and loosens them from the binding.

Moss

Moss will cling to the roof and retain moisture thereby destroying the roof. A roof that has a clear drainage problem resulting in stagnant water is also an attractive spot for moss to grow. Moss grows where water collects, even in roofs facing the South and under big shades of tree.

Treatment And Prevention

The most effective way of cleaning moss from a roof is by using a mixture of bleach and water. Apply it with a sprayer, allow the solution to dwell on the surface for about 15 to 20 minutes and then rinse thoroughly with low pressure water. To do this technique accurately, make sure to schedule a maintenance appointment with your local roof cleaning company or contractor.

Water Stains

Water stains can be a story to tell signs of impending roof leakage. Be sure to check if your shingles are intact, or head downwards to see if your attic or ceilings are showing any sign of leakage. White or yellow roof colours are usually associated with water stains

Water is said to be hard if it shows a high concentration of dissolved minerals like calcium or magnesium. If your home has hard water, you will notice mineral deposits or white stains on different surfaces around the interior and exterior part of the roof or building. While hard water does not pose an immediate health risk, the build up of mineral deposits it leaves behind can reduce the efficiency of your roof equipment and cause the exterior to appear unclean.

Similar to algae type of stains, attempting to power wash or scrub the roof surface can potentially make things worse. Alternatively, you can try fading the traces of damage with a vinegar solution, which works to slowly dull mild stains without posing risks to the animal or plant beds around your house. If you are considering using a harsher home remedies, consult a roofer and inquire about the better solutions that adhere to shingle manufacturers specifications.

If there are signs of leakage, contact your local roofer immediately for repairs.

Trees And Plants Debris Stains

If you notice stains of unusual patches near large, overhanging tree branches on your roof, they may be due to seeds, berries, leaves and other debris falling and then decaying on the surface of your roof. While most home inspectors will agree that we ought to keep shrubs at least 24 inches off of the building walls, and that trees within 5 feet of a building wall will pose a risk of damaging the structure by root pressure or impact. But the risk can vary depending on the species of the tree. Hence, there is no arbitrary correct distance for trimming trees back around a roof.

Prevention And Treatment Of Stains From Trees 

Remove Or Trim Large Or Tall Unhealthy Trees

A big tree in poor health condition can fall or be blown onto the building by wind or storm. This is why it is important to cut off dead branches entirely from any tree near your house. You can also call tree experts to come and assess the health impact of large trees near your building and allow them to do the trimming where necessary because they know the procedures for trimming trees.

Remove Dead Branches

This will prevent dead branches of trees from falling onto your roof and cause damage

Prevent on-roof debris accumulation; avoid allowing tree leaves and debris to accumulate on your roof. When allowed to accumulate on your roof, they will cause stains and long term wear and tear of the affected areas.

Reduce Roof Gutter Clogging

Trim back branches whose pine needles or leaves are falling into and clogging gutters. The amount of trimming and safe distance depends on the home, roof slope, roof drainage system, and the height and health distance of trees near the building.

Removal of moss and algae; remove moss, algae and probably fungal growth on some roof surfaces by reducing shade on problem areas of the roof.

Other Causes Of Roof Discolouration Or Stains

Beside algae, moss and hard water build up, there are other issues that can cause the appearance of stains on your roof.

Asphalt Bleed-Through

If your roof has reached the end of its lifespan or the materials used are inferior, you may notice black streaks across your asphalt shingle roof. When asphalt shingles start to break down, the black pigment from the asphalt is allowed to come up to the surface. 

This process is what roofing professionals call asphalt bleed-through. As soon as you see the signs of asphalt bleed-through, you should consult with a roofing contractor to see if replacement is required or not. Have it in mind that asphalt bleed-through can look a lot like algae stains because both of them have black discolouration on the roof.

Rust or chimney stains

Rust stains normally appear in areas surrounded by metals, such as your chimney. These are any red or brown spots hugging a portion of the chimney sitting on top of your roof. This is a clear indication of rusting, a common type of roof staining problem. It could be as a result of improper combustion of wood, coal, oil fired, gas fired or heating appliances vented above the roof.

Treatment and prevention

Rust stains can be cleaned with oxalic acid as they are very effective tools to remove and prevent rust. Remove vines from chimneys and from building walls as well.

White stains on slate roofs

Efflorescence, or the powdery deposit of salts from rainwater, is often visible on concrete and natural stone surfaces. These specks of white-coloured crystalline can sometimes appear on roof tiles or shingles. Fortunately, efflorescence is removed by natural weathering. As rainwater is slightly acidic, it gradually dissolves and washes away the deposit. 

If you want to dissolve efflorescence more quickly, applying pressurised water may do the trick, but remember that most professional roof cleaners will not advise homeowners to take the do it yourself approach due to some potential damages that may come up.

 

Light spots on roof shingles

As time goes on, a black or dark coloured asphalt shingles may appear lighter and patchy due to natural ageing, different weather conditions or poor maintenance practices. If you notice that your roof shingles appearances are inconsistent and unappealing, it is time to do the needful by inspecting the affected area. Look in the gutters for signs of ceramic granules, and the protective coating of asphalt shingles that have been washed off. See if the shingles are curling, broken or cracked. 

How Often Should You Have Your Roof Cleaned?

Frequent roof cleaning not only saves you money by maintaining a fully functional roof, improving the appearance of your property, catching any minor repairs before they become serious issues, and extending the lifespan of your roofing system, but it also protects you and your family. 

Generally, it is a great idea to get your roofs cleaned by professionals once every 12 months. However, roof cleaning frequency might vary according to the location of the building, the condition of the roof and other factors. A home’s roof should be cleaned within the first five years of installation and then every two to three years afterwards. However, homes in tropical areas or homes located near beaches, warehouses, production facilities, airports, busy roadways, and homes near lots of mature trees may need a yearly or more frequent cleaning.

  • For homes in tropical areas or humid climates that are prone to mould, moss, algae or lichen growth might schedule for annual roof cleaning in order to kill the growing spores and roots of these microorganisms.
  • If you live in an area with a regular stormy season, consider cleaning your roof after a strong storm has passed through your area.
  • Open fields or any garden nearby might mean layers of pollen and other plant residues winding up on the roof of your house. Annual roof cleaning is recommended for homes situated in this kind of area
  • Mature trees produce lots of debris that falls directly onto a roof. This might be in the form of leaves falling off and twigs. The more mature trees on your property, the more often your roof needs to be cleaned.
  • Older homes often require roof cleaning. This is to uncover areas needing repairs. The existence of cracks, or chips on older buildings gives access for the settlement of debris which damages the roof shingles, tiles and flashing as they build up.
  • Areas of construction zones, production facilities, airports, and busy roadways allow for tremendous accumulation of dust and other airborne debris. As a result of this, your home’s roof will require annual power washing in order to keep the roof clean.