Lichens (pronounced LY-kens not litchens) are slow growing fungi and are actually a good indicator of a healthy environment.
Lichen and moss can grow on roof tiles but this does not indicate a deterioration of the tiles, nor will it affect the performance of tiles.
Lichens are unlikely to make any significant difference to water absorption through the tile, even though they obviously can hold more water against the tile for a longer period.
Lichens and moss can be removed by:
- High Pressure Cleaner – You can hire a medium to high pressure cleaner to remove lichens and moss but be careful that you do not blast holes in the valley flashing or gutters if they are rusty. Also take care not to damage the mortar or tiles as they can become brittle over time.
- Stiff Bristle Broom or brush
- Bucket
Materials
- Copper Sulphate (bluestone) – Can be purchased from your local hardware store. Two kilograms should treat an average house; or
- Household detergent or bleach. Note: While lichens may succumb to household bleach or detergent, there is no long-term eradication effect.
Step 1 – Remove all dirt, moss, lichen, mould and all other surface contaminants by detergent (or bleach) washing and using a stiff bristle broom or brush.
Or
Step 1 – 2kgs of copper sulphate to 45 litres of water should treat an average house. Follow the manufactures instructions to remove the lichens and mould.
Note: The bleach and copper sulphate will corrode the coating on gutters. This can be minimised by running water through the gutters during the operation, but light corrosion could occur as the growths may retain some corrosive solution whilst dying and dispersing.
It is important that in both cases, you the disconnect gutters from any rainwater tanks until after the first rainfall to avoid possible poisoning.
Be careful that while cleaning the tiles you do not crack them.
A Guide to Removing Lichen And Moss On Roof Tiles,
Thanks for the useful information. This job is coming up soon. It’s nice to know what I’m in for =)
Does steam cleaning lichen from roof tiles pose the risk of increased chance of water seepage through to the ceiling? I have been told that lichen can act as something of a sealant stopping water from seeping through old and cracked tiles and that, when removed, the water just seeps through unhindered. Is this correct?
Thanks for dropping by!
As lichen is organic matter, it is not able to act as an effective sealant.
If you have cracked tiles I would strongly suggest you either replace them, or if they are only hairline cracks, fill them with a suitable silicone sealant (you may wish to talk to your local hardware representative for further advice).
Aging tiles do become brittle so be careful when you walk on them.
Water entering your roof space could be caused by a number of factors i.e. Cracked tile(s), mortar cracking away from ridge or capping tiles, blocked gutters, etc.
My housd roof is with glazed terra-cotta tiles newly built in 2003, the roof started showing black stain 3 years after, and gettiing worse in 2008, the stain is so severe that whole roof was so blaken as looked like had been caught by fire, the tile manufacturer checked and said it was caused by a kind of fungus. Later I had called in roof cleaner who used high pressure water washed and clean entire roof area, it looked like new roof after cleaned, but within 6 months the roof showed black again (not green or dark green) It can be easily washed off by high pressure water. It has no big tree not to the roof area (2-story building. Now whole roof area has return to the worst condition. Please advise if your method could cure the problem, or any practical advice will be apprecaited.
Hi Faming,
While black fungus will not damage your roof, it is not visually appealing.
In addition to the above two methods, a product with oxygen bleach should also remove the fungus. It is not necessary to use a harsh chlorine bleach.
Mix it with water, wipe down the roof and let it sit for approximately 20 minutes. You can then use a stiff bristle broom to brush it off.
Try and get as much off as possible.
This will be a regular maintenance task if the above methods do not permanently eradicate the problem.
I am considering re-roofing my house with fully glazed terracotta tiles. I assume that a glazed tile will be less susceptible to succumb to lichen and moss than a non glazed one. Is this a correct assumption?
Thanks, Michael
Hello Michael,
I am not aware of any studies that have been independently conducted to answer your question.
I think you will find that no roof tile manufacturer will provide a guarantee against lichen growing on a tile; especially in the right environment.
Sorry that we can’t be of more help!
Can lechin and moss cause water to seep through to the inside ceilings. We have inspected our tiles and there is no cracks but in some spots water has entered, marking the ceiling
Hi Alice,
It is more likely you have a broken or cracked tile (This could have been caused by someone stepping on it or a fallen tree branch).
Sections of pointing (The mortar that binds the ridge capping together) may have dislodged or fallen out.
Flashing, the waterproofing material around air conditioners or vent pipes may not have been installed correctly or deteriorated over time. Blocked gutters or valleys are also a common culprit for a leaking roof.
i have green mould on half my roof ,in the shaded areas,and black mould on the rest .
i have presure cleaned it spot less, but black mould grows back practicly over night.
as i have a laarge roof i heard “pool clorine”
watered down ,will do and will go further,thus cheaper.and cant i leave the mixture on ,surly it will be killed in strenth over time ?
any ideas in the watering down ratio?
black tiles seem to be the worst.
Hello Graham,
I would not be too keen to use pool chlorine for the following reasons:
Calcium hypochlorite, commonly known as ‘pool chlorine’, comes in a powder or tablet form. When dissolved in water it creates an oxidising agent which kills bacteria and algae and also acts as a bleaching agent. Sodium hypochlorite is the liquid form.
Roughly, household bleach (non-scented) is about 6% sodium hypochlorite by solution; liquid pool chlorine is 10% -12% sodium hypochlorite by solution and granulated chlorine is approximately 65% calcium hypochlorite.
Therefore granulated and liquid pool chlorine is very caustic and any metal i.e. gutters and downpipes would need to be thoroughly rinsed straight after application. You would also need to be mindful where the water ends up after being washed out of the down pipes.
Chlorine must also be handled with great care, see A Guide to Swimming Pool Chemical Safety.
Even the above will not guarantee the lichen will not return.
Hi,
I have a clear ? polycarbonate roof over a patio, and it has some fungal growth that a broom and a high pressure hose will not remove. What is the best way to attack this job?
Hi Chris,
In this case I would recommend you contact the installers or manufacturers and seek their advice as to what chemicals are appropriate/compatible to use on the sheeting. Some chemicals can affect particular coatings and finishes.
How can I remove lechin from colourbond roofb
You can prevent lichen, moss and most other fungi growing on your roof by installing a copper bar, copper rod or copper wire along the roof top ridge. Ideally it should not touch the roof but be suspended just above the ridge capping by using spacers.
How does it work? Every time it rains minute particles of copper will wash over your roof preventing lichen, moss or fungi growth. This old method is extensively used in Europe, England and USA and is often combined with lightening protection. Want proof? Watch video now: http://www.youtube.com/watch?v=G93vvGutaLs
Hi
We have Terracotta tiles on our home which have fungi growing on them the last few years. We have a product called 30 seconds but have not used yet. It was suggested to us that perhaps our tiles weren’t sealed when house was built as we are the only house in our area with this problem. Also no part of the roof is shaded all day.
Note: there are many other Beechwood homes in our area without this problem, built at the same time late 1990′s.
Note: the capping on our roof also isn’t the best , my husband has had to repair some of this & thinks the whole roof capping needs to be done.
HOPE you can help with some advice.
Thanks Lynda
I must say that I am very sceptical about the use of copper wire on ridge capping to control moss and fungus. I am in the process of refurbishing my deseased inlaws home in Gippsland and have recently had the tile roof pressure cleaned, valley irons replaced and repointed (By a very dodgy tradesman – but that a story for VCAT). The south facing roof had a huge buildup of both moss and lichen and it had a heavy braded copper wire running over all of the capping. They were from Latvia so maybe that’s where they got the idea from. The wire had been there for a long time and was obviously inneffective.,
Copper will NOT control lichen, it’s handy for snails but useless on lichen. Pressure clean, patch/replace all damaged capping and then seal it, DO NOT USE house paint, different beast.
To be honest if it’s that bad PAY a professional roofer, one that is registered and accountable and just get it done properly. Check with you Local/State Govt about registered builders if you don’t know how to validate them. Oh, 3 quotes would be my minimum before committing.
hi there
i live in south st marys nsw
i have a glazed terracoota roof tiles on my roof and my house front is facing south it does not see the sun much in winter but in the last few years i have seen a lot of greyish looking grassy moss grow wild especially in shaded and under the antanna areas..i have tried to spray it with a glysophate weed killer solution which was recommended to me by a roof cleaner but its not doing the job and would like you to tell me what is the best products to use and can buy it from pls.. cheers..jamal
Can i apply a clear concrete sealer like the type you can applly to normal concrete once i have cleaned my concrete tiles? i think it is water based and would soak into the tiles well. It would also be an inexpensive way to seal the roof if it works. my tiles are around 40 years old but they are still solid. The harsh sun has has taken them back to the bare concrete and the absorbe the rain now.
You can buy 30 Seconds roof treatment http://30seconds.com.au/products/roof-treatment/ to kill and help prevent lichen, moss and mould. But, I prefer to use a pool algaecide, where the active ingredient and results are the same. 30 seconds has approx 95g/l of benzalkonium chloride, whereas the algaecide has 150g/l and is much cheaper. This has to be mixed to 4 parts water to 1 part algaecide and sprayed via pump pack. After 3-4 months you can see the results.
thank you.. Nicely written
I have a fibreglass boat and the deck is a cream colour. It has been sitting for a while and developed small grey coloured patches on the surface. Any idea about the easiest way to clean this?
I am preparing to sell my house and have black cement roof tiles with lots of green moss on them. i have been getting quotes, but several are saying that cleaning the tiles will end up discolouring them and therefore the tiles will need to be painted. Is this really necessary, or can a good pressure clean with appropriate solution do the trick?