Whole Lotta Tiled Roofs! Looking for Advice!

So in my area in Australia we have a whole heap of tiled roofs. The majority of them have lichen on them. The dilemma that I have is the whole softwashing/pressure washing debate when it comes to roof cleaning. I’m already aware of most of the pros and cons of both methods. I’ll just list a few so that I can demonstrate the extent of my knowledge in the area (by no means expert). Please bear in mind that I’m talking about removing lichen from tiled roofs. In my area its either tiled or colourbond roofs. The tile roofs tend to be the dirtiest as they are on most of the older homes.

Softwashing Tile Roofs

Pros- Low pressure treatment, can apply from the ground, not risking breaking tiles or water ingress, cleaning solution attacks the route cause (organic growth) and kills it

Cons- Due to the stubbornness of lichen it won’t simply fall away as soon as the SH does it’s work. If you apply an SH mix it will die but will then take another 8-12 months for it to fall off with the action of the wind/rain

Pressure Washing Tile Roofs

Pros- Instantaneous results due to using the force of water to remove the lichen
Cons- Risk of cracking tiles, water ingress, falling from roof

I guess my query comes from the fact that most homeowners are looking for quick results. Most homeowners are wanting to walk outside and look at a clean roof, not have to wait for 1 year for it to look better. However I know the pressure washing carries some inherent risks when it comes to cleaning tiled roofs so hence why I’m looking for your guys opinions.

For reference I have a pretty decent setup on the back of a ute. 5.5gpm 3k psi hot/cold pressure washer and a 12v softwash system with a proportioner. I also have a telescoping pressure pole (yes, I’ve heard plenty of people laugh at them and dismiss them, but I view it as another tool that can come in handy from time to time)

Some operators pressure clean tiled roofs day in and day out and then there are others who hardly do them or if they do then it’s softwash only and explaining to the client that it takes a year before you’ll begin to see any results.

What are your thoughts, how do you go about cleaning tiled roofs with lichen on them???

I’ve never treated one that took 12 months to flake off. What’s your idea of a strong mix for lichen?

That’s just what I’ve heard a reputable local contractor say in order to help set client expectations. For Lichen I’d say 4-5%. What do you do?

I do the same, 50/50 mix on every roof. Turn up the soap and drown it. Cling time and penetration important for lichen, it must get down to the roots to release especially in the hot blazing summers you get where chemical flashes off quick. If it doesn’t turn white the jobs half done, hit it again.

In your experience, roughly how long does the lichen take to fall off the roof?

Most reviews come in 6-12 weeks later so I guess there happy in a couple months. Of course it depends on the state of the roof if your talking about a carpet laid over a roof might take longer. Average residential lichen job around here spotty lichen all over the roof. Just depends what challenge is presented to you.

I’ve found that if it’s very dry, I take my shooter tip and wet down roof pretty good, especially in the summer. Let any excess water drain off for about 5-10 min. That helps soften it up and it much more receptive to your chems. Kind of the same concept when you’re watering a plant that the ground is hard, the initial water runs off. Let it soak for a min and then will absorb the water much better.


That’s a great idea.

Do you come across much lichen in your neck of the woods?

oh yeah, plenty. Typically though we’ll start getting algae growth first and then the lichen starts growing along the bottom edge of the shingle.

I’m talking concrete tiled roofs, just making sure you’re not getting that confused with asphalt shingles

Lichen is lichen, whether on rocks, trees, asphalt, slate or tile roofs, it’s still lichen.