By Daniel Weadley
© DanielsRoof.com

The simplest and often the cheapest way to effectively remove roof moss is to instruct a general roofing company to physically scrape it off. Most local roofing contractors will consider undertaking this type of work. It is something I have done many times and in my opinion is safer and not as messy as pressure washing.

While the contractors are on the roof they can also check for any damaged or broken tiles and replace them. It is also a good time to check the condition of the cement and chimney (if you have one).

After the moss has been removed and the gutters given a thorough clean out, they can spray the roof tiles with a fungicide moss killing chemical, there is a list of readily available moss killers on this page.

Why not consider installing a gutter guard to protect the guttering from leaves and other blockages? Most gutter guards tend to block and clog with bits of roof moss that wash down from the roof. If you first scrape the roof of moss, the guards will work much more efficiently and keep out large leaves. I have tested various gutter guards here.

How Difficult is it to Clean a Roof by Removing Moss?

Access is the big issue here but in most cases the moss will come off very easily. If the roof is wet it is much more difficult, moss easily turns to mud and it can be difficult to clean a roof in such conditions. It’s always best to carry out this type of work in the summer or at least when the roof is bone dry.

The photo below shows one of my roof moss removal projects in progress, all the moss was removed with a trowel followed by a brush down with a stiff broom. No messy pressure washing equipment was used on this roof or the hundreds of others I have worked on.

Here are some tips for roof moss removal:

• Use the correct access equipment – safety first
• Carry out this type of work when the roof is dry
• Start from the top of the roof and work downwards using a trowel to scrape off the moss
• Then use a stiff broom sweep off any loose moss and dust
• Replace any broken tiles and clear out gutters
• Check condition of cement work and repair as required
• Spray roof with a fungicide moss killer to kill off any roots and prevent early re-growth

Should I Use a Pressure Washer to Clean My Roof?

Using a pressure washer is one way of removing the moss along with any other dirt and grime. However if you have broken tiles on the roof then there is a flood risk and old tiles can suffer from discolouration as the loose grit on the tile surface is blasted away.

Most professional roofing companies tend to stay away from using pressure washers, so that leaves the cowboys and questionable firms. I have noticed plenty of “Roof Cleaning” companies advertising their trades recently. Most will pressure wash the roof and apply a paint/sealant to the tiles.

Personally I would never use a pressure washer to clean a roof as it’s terribly messy and aggressive, also I have observed that the sealants which are usually applied afterwards tend to be short lived.

My Photos of Roof Moss Removal

I didn’t use a pressure washer or apply a coating/sealant to any of the roofs shown in the photos below. In my opinion they look great:

Fragile Clay Tiles

Clay tiles tend to break quite easily and one should avoid walking on them unless it is absolutely necessary. Roof moss removal is rarely a necessary project and even if it is was, I wouldn’t recommend walking on clay tiles, the risk of causing damage is just too great.

In my opinion the best option is to use a long reach pole with either a scraper or wire brush attached to the end and try to remove as much moss as possible without actually walking onto the tiles.

This work could be dangerous if done from a ladder but an access tower raised to gutter height would be perfect. Once the excess moss is removed a moss killer can be sprayed onto the roof, this will kill off any bits of moss and prevent regrowth for a few years.

I would then suggest re-applying the moss killer every 2-4 years to inhibit further growth. This method may seem a little old fashioned but in my opinion it is the only tried and trusted technique that is affordable and doesn’t involve pressure washing. Moss killer chemicals can be purchased in concentrated form, ready to be diluted and applied via a sprayer. They are not too expensive and can be purchased from online stores such as Amazon.

Slates

Natural slates are often used as a roof covering, moss can grow on them but tends to occur on the overlaps and joints. It’s quite rare to see a slate roof totally covered in moss.

Because slates are more fragile than concrete tiles and because they are difficult to walk on, I do not recommend climbing onto the roof to scrape or pressure wash the moss off of them. Instead, I would use a long reach pole and try to brush off the excess moss. Then apply a moss killer chemical using a sprayer, these can be purchased from Amazon and have a reach of around 5 metres.