Roof Moss Removal [NZ Guide]

Moss can spread quickly on rooftops and other parts of your home’s exterior.

Although it may seem a charming aesthetic, a mossy roof can be dangerous for the health of your house and your family, so it’s important to learn to deal with moss on your roof before it becomes a major problem. 

In this guide, we’ll outline exactly how to remove moss from your roof, as well as provide steps to stop it from growing back.

We’ll cover:

  • What moss is and where it comes from
  • Why it’s important to remove moss from rooftops
    • Mould
    • Holes and roof damage
  • How to remove moss from roof tiles (and prevent it from growing back)
    • Removing existing moss from your rooftops: step by step
    • Preventative measures to stop moss from growing on your roof

First, here’s a quick overview of why roof moss exists and what it actually is.

What is Moss and How Does it get on the Roof?

Mosses are a collection of tiny flowerless plants that thrive in damp conditions.

Since roofs are the part of a house most exposed to rainwater, they’re easily overcome by moss once a colony has started.

This is especially true if you’re living in a particularly wet area.

How does moss grow on your roof?

Moss is nonvascular, which means it doesn’t have roots. Because of this, it can spread very easily through spores that are picked up by the wind, fall from trees, or transported by animals.

Just a few spores landing on your roof is usually enough for it to spread and grow quickly –  that’s because the moss doesn’t require the same earthen conditions as most other plant species in order to survive.

While some people might consider moss on the roof to be something of a rustic addition to their home, the truth is that over time it can become quite dangerous.

The Dangers of Moss on Rooftops

There are two major reasons why it’s essential to keep your roof free from moss:

  • Mould
  • Holes

Each of these conditions comes with its own problems, so we’ll break them down.

Mould on your roof

As moss grows and spreads, it can become a large blanket of plant matter that retains moisture. This moisture can lead to rot, bacteria, and mould growth.

Roof mould can severely hurt the lifespan of your roof, leading to big expenses in the future.

On top of this, mould can attract unwanted animals, such as rodents or insects, that feed on the mould and may be inspired to seek more delicious treats elsewhere – like the inside of your home, for example.

Holes and tile damage

The insidious nature of moss means it can creep into the crevices between your tiles or shingles and your roof.

This can cause parts of your roof to lift, revealing holes where water could leak through.

But that’s not the worst of it. In places where the tiles or shingles haven’t lifted, but moss has grown underneath them, tiles may have come to rely on the moss for support, and removing it later on can cause even more damage.

Luckily, there are ways you can remove moss safely and lower your risk of regermination occurring further down the track.

Let’s lay them out.

Cures and Preventions For Roof Moss

Online, you’ll find many “solutions” for removing moss from your roof. These can range from reliable and well-informed to, well, uninformed guesses.

Here we’ll explore the best options, and offer advice on how best to go about them.

As always, the most important thing when working on roofs is safety.

Before you go attempting any of the below-listed techniques, ensure you have the following safety precautions in place and equipment handy:

  • Grippy, well-fitting footwear.
  • A ladder.
  • Safety goggles.
  • Rubber gloves.
  • Someone that knows where you are in case of an emergency.
  • Sun protection.
  • Strong knowledge of which parts of a roof are safe for walking.
  • Old clothes for working in – it’s a dirty job!

It’s best to do roof work on an overcast day when possible. Never attempt to work in the rain unless you’re a professional roof worker and can do so with complete confidence.

Once you’ve got everything you need, it’s time to get started.

How to clean moss off rooftops

Step 1) Wash the roof with a waterblaster

Spraywashing is the easiest method for removing moss off roof surfaces.

Begin at the apex of your roof. Make sure your waterblaster is at the lowest possible setting. Alternatively, if the shingles on your roof are particularly old or already damaged, you may want to use a regular hose instead.

Point the waterblaster at a slight angle and always work methodically in a downwards direction to prevent lifting or damaging any shingles.

It’s possible to use a mixture of water and bleach for spraying but you ought to consider the implications of using bleach before doing this. With bleach, you run the risk of damaging surrounding flora and staining your roof. It can also be harmfully toxic to humans if ingested.

It’s also important to stress that you should be confident with heights, surefooted, and follow all health and safety protocols when attempting roof work.

Better yet, hire a professional to do this work for you.

Here is an example of a moss-covered roof, before and after a professional removal has taken place:

Step 2) Scrub tiles with a brush

Once thoroughly washed, use a scrubbing brush or long-handled soft bristle brush to remove the more stubborn moss on roof tiles that remains after using the pressure blaster.

Be sure to get into all the nooks and crannies where moss has formed: just a single spore is enough to restart a new colony.

Step 3) Roof moss treatment

Since moss can grow back quickly if not fully removed, it’s best to also apply some type of moss removing agent to the washed and scrubbed roof.

If you used bleach, this step may be unnecessary, as the bleach should kill remaining moss spores by itself.

Once moss remover has been applied, allow 20-30 minutes for it to do its job.

Step 4) Wash the roof

Assuming you followed Step 3 and have applied moss remover to your roof, the final step is to wash the chemicals off your roof with clean water.

This can be done with buckets, though a hose is safer, and extra care should be taken working on the roof as some chemicals may cause extra slippage.

Keep reading to learn how future moss growth can be reduced and prevented.

Getting rid of moss on the roof for good

There are a few preventative measures you can take both before moss has a chance to grow and after you’ve safely removed existing moss from your roof.

In the case of before, here are some great tips for limiting your risk of moss exposure:

Trim any overhanging tree branches

Moss can often fall from the branches of trees that brush against or lean over your rooftop.

By removing any overhanging branches and leaves, you’ll reduce the chances of moss spreading onto the house.

Note: Be sure to hire a professional arborist to manage this for you, as tree work can be dangerous and should always be completed by a professional.

Install zinc or copper strips

Long strips of zinc or copper attached to your roof can help rainwater to wash away moss before it has a chance to spread too widely.

The strips can aid rainwater in reaching the shadier parts of your roof, where moss is more likely to grow.

Be proactive about your roof care

Lastly, there are many ways for moss to find its way back onto your roof.

If you want the best chance at fighting it, keep your roof free of detritus such as fallen leaves, seeds, and other debris that might carry moss.

Regularly clean your gutters and keep an eye on the state of your roof at all times, so you’re aware as soon as moss starts to grow and can deal with it quickly.

Would You Rather Leave it to the Professionals?

If you’d rather get a professional to remove the moss from your roof, fair enough! Working with moss-killing chemicals and waterblasters at height isn’t everyone’s cup of tea. 
Get an instant quote here, and leave the precarious scaling of buildings to us.