How to kill moss on roofs

A moss covered roof will be too much for most gutter guard products
A moss covered roof will be too much for most gutter guard products

Moss covered roofs

Roof moss affects many homes the world over and is a constant frustration for home owners. The growth can easily be washed down into the gutter causing blockages or even worse it can collect in the underground drainage system and cost a fortune to clear. It is rare for leaves to cause such blockages as they usually blow away with the wind. It is moss that settles in the base of the gutter and breaks down into thick mud which cakes the inside of the guttering or downpipe.

While there are many gutter guard products on the market, they do not filter out 100% of the debris and are generally costly to install. You may also find that flimsy plastic guards simply collapse under the weight of the wet moss. It is much better to tackle this issue at the source.

Gutter protection products can more effectively keep leaves and pine needles out when they are not struggling to cope with excessive moss.

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Roof moss removal in progress
Roof moss removal in progress

How to best remove the moss

When most people consider removing moss from their roofs they assume that a high powered pressure washer must be used. That really isn't the case and used on some tiles can leave the roof with a colourless appearance. An inexperienced contractor can even flood the loft or blast the moss onto your neighbour's property.

The best way to kill moss is to use the old fashioned and "tried and trusted" method, which is to wait until a dry day and then use a scraper to lift the moss off the tiles. You will be surprised at how easily it comes off. Most of the moss will just fall onto the plastic sheet you placed over your patio or lawn.

As you see from the photos on this page which were taken in October 2010, moss removal needn't be a costly or messy project. Access to the roof is the most difficult part, once you have the correct access equipment such as ridge ladder then it is quite easy to actually remove the moss. A general contractor can do it with ease.

Looking at the photos on this page you will notice light patches where the roof tiles where once covered by the moss. From ground level these are much less noticeable and after time the roof will "weather" back to a more even colour.

The black marks that you see covering the tiles are not just general dirt but are organic growth, they will be killed off if you use a moss chemical.

Prevent moss re growth with a chemical killer

Once the moss has been completely removed, the roof swept down with a broom and the gutters have been emptied, it is then a good idea to spray the roof with a quality moss killer. Each country will have different regulations for the use of chemicals so this isn't the place for me to advertise individual products.

Here are some general suggestions for you:

  • Always remove the moss first - otherwise your gutters will become blocked with dead moss
  • Always disconnect any rain collection barrels/water butts
  • Always cover fish ponds
  • Never apply when rain is imminent
  • Never mix chemicals - even if they appear inactive
  • Never use grass moss killer as it is far too weak

I do not agree with tradesman and other people who believe that the moss should be sprayed first and then removed. You are likely to suffer from gutter blockages for many months and in reality it's just a waste of chemicals and money. It is far better to remove the moss and kill off any spores/roots this preventing early re growth.

Related Products

Wet and Forget 10587 1 Gallon Moss, Mold and Mildew Stain Remover
Wet and Forget 10587 1 Gallon Moss, Mold and Mildew Stain Remover

Apply this moss killer to any exterior surface and it will re activate whenever it rains gently killing off mould and moss over time.

 
GutterBrush Leaf Gutter Guard for Standard 5 Inch Rain Gutters - 120 Foot House Pack
GutterBrush Leaf Gutter Guard for Standard 5 Inch Rain Gutters - 120 Foot House Pack

Gutter guards work best after any excessive moss has been removed but they do help.

 

Are roof coatings or sealants required?

There is no need to apply any type of paint, coating or sealant after you have killed the moss with a moss killer chemical. They do not offer long term protection and after a few years of rain, sleet, wind and snow they will have suffered from so much general wear and tear they may even flake off or become patchy.

Considering the cost of applying a roof coating and it's short life span it is never a recommended product. Applying a roof coating may also invalidate any guarantee that is offered by the tile manufacturer.

How to ensure the long term prevention of moss growth

Using manual removal techniques and chemical is the most economical way to rid the roof of this growth and prevent short term re growth. But what about long term?

There are two options to permanently prevent re growth.

Re apply the moss killer chemicals, such as Mossgo after 2-3 years thus removing the need for the roof to be re scraped. Here you can find a list of treatment products to kill moss. This option is preferred as while on the roof you can check for any damaged tiles and give any cement, lead or gutters a visual inspection.

The other option is to install copper strips after the moss has been manually removed and the roof sprayed with a chemical. This page explains the do's and dont's on using copper as a moss killer.

Health and safety first

I really hope you have found the contents of this hub useful. Please remember that it can be dangerous to climb over roofs especially if you not familiar with this work. If in doubt contact a general roofing contractor and ask for a quote for manual moss removal and spray with fungicide. To save on costs you can even buy the chemicals yourself on the internet.

This hub refers to moss growth on concrete tiles, other surfaces such as bitumen roof felt may require different removal techniques. If in doubt do a test patch first.

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Comments 3 comments

simon cowham profile image

simon cowham 5 years ago from Wellington

Roof moss and lichen can cause serious damage to roof tiles. During frosts the water inside the moss expands and can cause pitting and cracking of the tile surface. With concrete interlocking tiles, the channels can become blocked causing leaks inside the property. Your article outlines some good ways of eradication. Thanks.


billy drew 3 years ago

very practical usefull info,this has worked out well,thankyou for all your ideas,just don't rush thing when up on the ROOF,


Ashley 21 months ago

Would coating the roof make a difference? We have a good change of getting moss on our roof, so I want to prevent it as much as I can. We're getting the roof, we have now replaced, so it's the perfect opportunity to make preventative measures. http://www.stetsonpainting.com/what-we-do/roof-coa...

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