Forget Roof Cleaning by Jet Washing – Try This Method Instead

Are you thinking of having your roof tiles jet washed? Think again.

As stated by several roof tile manufacturers and the UK’s Trading Standards organization, pressure washers CAN damage roof tiles, strip the surface granules from the tiles and SHORTEN tile life expectancy. There is also a risk of flooding to the loft space.

Read more about why pressure washing a roof is a very stupid thing to do

Roof cleaning can be achieved by manually removing any excess moss and then applying the correct chemicals to the tiles. This approach doesn’t involve any water (no mess!)  and won’t damage the tiles. Any individual tiles that are damaged during this process can be replaced cheaply as roof tiles are not that costly to replace if all the scaffold and access equipment is already in place.

It does involve using some chemicals (such as BAC50) and also a good dose of patience!

Roof Cleaning by Using the Correct Chemicals

One of the most gentle yet effective ways to remove roof moss and clean the roof is by way of scraping. A normal 9″ trowel is suitable, if your roofing contractor chooses a dry day any moss will flake off the roof much easier and there won’t be any scratch marks on the tiles. This approach is recommended by Forticrete who are one of several roof tile producers in the United Kingdom.

If you are concerned about scuff marks to the tiles then a rubber scraper and stiff brush can be used. Remember – with this method there is no damage to the tiles and no flood risk, unlike other roof cleaning methods such as high-powered pressure washing.

Look at the photo below, the moss was removed with nothing more than a trowel and a hand brush, the difference compared to the mossy section of roof is striking.

Roof cleaning doesn’t need to involve power jet washing.

This photo was even taken before any chemicals were applied – what a difference! As you can see, there is no damage to the tiles, no scratch marks and the tiles have not been dislodged by the process.

Roof cleaning, moss removed from roof - without pressure washing

So Why Use Chemicals?

If you apply a fungicide/moss killer after the moss has been scraped off, it will soak into the tile and more importantly into the overlaps of the tiles and kill off any tiny moss spores. It will also kill off lichen and other organic growth on the tiles. This roof cleaning process can take some time after the excess moss is initially removed but there is no damage to the surface of the tile.

The application of roof cleaning chemicals will also prevent the moss from growing back for several years.

As a bonus, this chemical will also kill lichen, so those black marks on the tiles will fade away a few weeks after the treatment.

Which Chemicals are Recommended?

RoofCoatingScam recommends the following moss treatment chemical for roof tiles, paths, patios, fence panels, driveways and most hard surfaces:

No Pressure Washing. No Flood Risk. No Expensive (and Useless) Roof Coatings

As stated in other pages, roof coatings are often an expensive and short term approach to roof renovation/roof cleaning. There is a real flood risk, the coatings often look terrible after a few years and they being mis-sold by many many companies in the United Kingdom.

The manual approach to removing moss and applying a chemical maybe considered an old fashioned roof cleaning method but it is time proven and you certainly won’t have to worry about paint peeling off the tiles.

Did I mention that manually removing the moss/applying a fungicide is often the cheapest cleaning method?

Expect to pay around £500 for a semi detached house in Southern England. Compare that to £2000 for a roof cleaning and coating.

Roof cleaning photo

Roof cleaning without jet washing

Roof cleaning and moss removal photo

Roof moss removal in progress – no power washing tools used

Roof cleaning complete

Roof demossed, no mess, no leaks, cheap and affordable

How Long Does the Moss Killer Last?

Assuming that the roof isn’t under tree cover, the moss shouldn’t grow back for about 3 years, after 4 years there will be light growth.

For this reason, the homeowner should instruct a roofing company to re-apply the chemical every 3 years, thus preventing any moss growth and keeping the roof looking clean.

Moss killing chemicals are not expensive, expect to pay around £30 for enough to treat a semi detached property. A backpack sprayer costs around £25 and the work takes around an hour.

If you purchase a more expensive backpack sprayer (Hozelock 12 or 16 litre) then you will find they have a very long reach, about 6 metres! That is enough to reach the top of the roof from access towers erected to gutter height.

So once the moss is initially removed nobody ever needs to get on the roof again. This reduces the amount of foot traffic on the roof tiles. Remove the moss once, re-apply the chemicals from gutter height with a sprayer every few years – simple and cost effective!

This type of work is often carried out by traditional roofing contractors, although few roof cleaning/coating companies recommend this approach as it doesn’t involve pressure washers and expensive roof coatings/sealants.

It is possible to complete a roof cleaning project without pressure washing, but the chemicals do take a little time to work. Remember: the “dirt” you see on a roof is usually moss and lichen which can be treated and prevented with chemicals.

Can a Moss Killer be Applied Before the Moss is Removed?

This is a common question, can/should a moss killing chemical be applied to the roof before the moss is removed?

The answer is no.

First, you would need much more of the chemical as the moss would soak it up.

Second, thick layers of moss will prevent the chemical from soaking into the tile/overlaps.

Third, if you were thinking of applying the chemical instead of manually removing the moss with a scraper, then you would have a big problem – the dead moss would gradually wash down into the gutters and block them. It could take months if not years for all the moss to wash off the roof. Your gutters would need frequent cleaning and even then they are still likely to become blocked.

Advice From Tile Manufacturers

Marley Eternit, one of the  largest roof tile manufacturers in the United Kingdom responded to an email enquiry about how to clean their popular “Double Roman” type roof tile with the following statement:

We DO NOT recommend pressure washing your roof covering.

Forticrete, which manufacturers a variety of concrete tiles for the UK market responded to a similar request with the following statements:

Removal of moss should be done manually off proper roof access equipment to protect the tiles and operators.
This should be done with a scraper and stiff hand brush.

They added:

Power washing the tiles will remove fines in the concrete which will affect the lifespan of the tiles…. As a manufacturer of concrete roof tiles we would not advocate power washing or recoating tiles as this would invalidate any guarantee.

You can read more guidance from tile manufacturers, government bodies and consumer protection agencies here.

Which Chemicals are Best?

As we have previously stated, in most cases moss will not damage the roof tiles but can block gutters and drainage points. On certain roofs, such as those with a very shallow pitch, moss can potentially reduce the flow of water off the roof.

If this is the case (and very few roofs suffer from this issue) then gently removing the excess moss via traditional methods and treating the tiles/remaining moss with a fungicide is the best option.

Try any of the moss killers listed here, they can be used on tiles, patios and driveways etc. I have used all of them previously.

As general advice: RoofCoatingScam does not recommend regular roof cleaning just for the sake of improving the appearance of the roof. Foot traffic can damage roof tiles so we only recommend roof cleaning/de-mossing when it is absolutely necessary, ie when the moss is preventing water from draining off the roof.

Further Reading

Did you like this article? Why not “like” us on Facebook and then try one of the following links:

Is it safe to pressure wash a roof? (Advice directly from tile manufacturers)

Do concrete tiles need to be re-sealed?

Roof coating scammers found guilty in £2.4million scam (wow!)

Yet another conviction in the roof coating industry

Are thermal roof coatings the biggest scam in the roofing industry?

Cost and price guides for roofing related work can be found at Roofer’s Rates

Can You Help?

You can help spread the word about roof coating scams, miss-selling and bad business practice by doing any of the following:

Share and “like” this page on FACEBOOK – remember we are a small website with a limited budget, help promote us please.

Write about our website on your blog or any other social media platform.

Leave a comment/feedback for us below or answer our question/poll (located to the right of this page)

(Page updated February 2014)


24 Responses to “Forget Roof Cleaning by Jet Washing – Try This Method Instead”

  1. Alex DuncanJanuary 16, 2013 at 09:50 #

    Your average homeowner, in my opinion, should not be encouraged to apply moss killing chemicals, as not only are they dangerous to your health but improperly applied can also kill your plants and grass!
    And worse, climbing onto a high roof (or any roof for that matter) without the proper equipment is just not a good plan, please don’t do it, find a reputable roof cleaning company, or professional roofer who does this kind of work (be aware that the subject of tile replacement does come up regularly though!), but what ever method you choose, try and avoid doing it yourself.

  2. michiganepdmcoatings.infoMarch 5, 2013 at 08:01 #

    A unique feature of or roof cleaning solution is that in addition to containing mildew eliminating agents, it also contains mildew prevention property’s as well. Witch means your roof will stay cleaner longer saving you money.

  3. kc smith roofingApril 12, 2013 at 14:12 #

    Yes although pressure washing is probably the best way, it doesn’t quite always go to plan when using it with old tiles.

    With new tiles your fine, aslong as you are careful. Chemicals do work, but weigh up the obvious pros and cons first.

  4. jc property maintenanceJune 9, 2013 at 11:01 #

    As a company that clears moss your chosen method we are so pleased that you have made the public aware of this scam. We come across people who have been charged large of amounts of money for this shoddy work often pressured into orders by pushy salesman. it is often the elderly and vunerable members of the public. We also fit copper strips just below the ridge tiles so that when it rains a copper sulphate is produces preventing the moss from returning this is effective for up to 5m. Keep up the good work as a new company appears to be springing up every week with no or little roofing experience.

  5. GaryAugust 25, 2013 at 01:28 #

    We are a roof cleaning company with many years experience cleaning residential and commercial roofs every roof is different for many reasons so a thorough investigation internal and external is always advisable i do agree removing moss by hand but if this is the only option and i also agree with Alex Duncan
    regarding the dangers of DIYers but in our experience if you want the job done right the only way is pressure washing your roof at the correct flow rate and following the manufacturers instructions to detail when applying there products.
    Roof coatings are cost effective if applied correctly, new roofs with several years wear can also benefit with a good quality clear sealer for best results treat north and west facing views.

  6. Steven McGintyAugust 26, 2013 at 05:48 #

    Thank you for your good information, i have a roof but i believe the pressure washing is not the way to go.
    It can block up the down pipe so make sure you guard it doing it either way before starting job!
    With pressure washing i have had to re-point the roof which came off after doing the job several weeks later.
    I would scrape roof apply moss killer and put copper strip on , also re-point roof if needed.

  7. Colin EvansSeptember 13, 2013 at 10:19 #

    I have received two conflicting recommendations from roofing contractors. One says the moss on my roof needs removing and recommends hard brushing; the other says there is no need to remove the moss as it provides some protection to the roof. Who am I to believe?

  8. GarySeptember 20, 2013 at 09:21 #

    Proven by the university of Portsmouth moss,algae and lichen will shorten the life span of your roof moss will also add considerable weight to the roof area it will also cause capillary action resulting in unforeseen problematic issues do not scrape your roof tiles with metal objects use a rubber scrapper and brush if necessary or better still consult a good roof cleaning company who know what they are talking about.

  9. TomOctober 10, 2013 at 09:37 #

    This site contains the biggest load of nonsense I have ever read. I clean commercial roofs, including but not limited to; asbestos and cement sheets and also apply a protective, waterproof coating. The manufacturers specs of the coating is to pressure wash the surface to remove dirt and then apply the coating. This is standard practice on commercial properties to extend the life of the roof and even triple the lifespan. Cement tiles on domestic properties are much more dense and hard wearing than fibre cement so pressure washing would have no negative effect to the life span. Lichen and moss hold water therefore over time saturated the roof tile softening the surface. This site looks like it has been wrote up on one of those free website building companies by a disgruntled roof cleaning customer who chose a dodgy firm and wants to tar every company with the same brush. Very sad.

    • Mike RobertsOctober 17, 2013 at 12:40 #

      Agree 100% with Tom what a load of nonsense, as in any trade there are ‘dodgy’ firms around offering this service.
      We have been cleaning coating roofs for over 10 years, we can show clients roofs which we have coated in the past customers are thrilled with the results, many still use of for other services we offer.
      Who actually runs thsi site ?
      I notice its just an email really professional. It also suggets home owners carry sprayers upto guttering level to apply moss killers – That contradicts all Heath and safety directives plus working at height act. Just hope home owners have a enough common sense to read between the lines, this is site is obviously being run via someone like mossgo !

  10. Mr BaileyJanuary 2, 2014 at 14:08 #

    Thank you for your post. I was considering getting the roof cleaned professionally. Obviously not with a pressure washer, but they all seem to use them. I did scrape off a lot of moss by hand last summer.

    I have a problem as I have no head for height’s

    But I now won’t use a contractor.

    I have located Patio Magic at Homebase. Saves ordering by post.

    Wouldn’t Jeyes Fluid have been good also?

  11. JOHNJanuary 18, 2014 at 22:05 #


  12. alex duncanJanuary 19, 2014 at 20:03 #

    Jeyes fluid does indeed work quite well on moss, copper strips on the other hand don’t.
    I’ve cleaned many roofs that have been “protected” by copper strips and I’ve even seen moss growing on the copper itself, so not worth it IMO.
    Pressure washing has its place for roof cleaning, generally best used before a coating though, and not just for cleaning, as depending on how it is done it “can” remove a fair amount of material from the tiles.
    And my last point (again) is to ask home owners not to attempt to clean their own roofs without the proper equipment and safety gear, as it shouldn’t cost fortunes to have it done professionally and it is much better for your health.

  13. DanJanuary 26, 2014 at 09:52 #

    I completely agree with Tom and Mike. Scraping the moss of yours and then treating with fungicidal wash is fine but this will not clean the actual tiles like pressure washing will. Concrete and clay tiles are actually very tough durable things which are certainly not damaged by pressure washing at correct pressure. The coatings really show a beading effect when water hits coated tiles thus proving genuine water resistancy. Homeowners don’t be fooled by the nonsense on here.

  14. TomFebruary 11, 2014 at 11:31 #


    I can see you actually know nothing about roof tiles. The manufacturer, Sandtof states that scraping is a big no, no as it scratches and dislodges the tiles. It also stated that a Lowe pressure wash is the recommended way to clean a tiled roof. Please stop putting your opinions as facts, as it misleads people.

    Thank you,


    • John WestFebruary 11, 2014 at 12:20 #


      I know for a FACT that it is impossible to remove roof moss using a low pressure wash, I have tried it myself. The pressure must be increased to a level where it also damages the surface of the tile, it strips the colour and/or granules from the surface of the tile.

      Sandtoft does not recommend using a HIGH powered pressure washer on their roof tiles.

      I find it deplorable that you are stating that you use a low pressure when the only way to remove moss is to use a high pressure.

      Marley Eternit states the following: “The use of high powered jet washes is not recommended as it can damage the surface of the slate or tile, thus reducing its expected life considerably.”

      Marley also state: “There are several methods for the removal of moss and lichen: Spraying with a toxic wash, copper wire, scraping”

      Trading Standards also state the following: “We do not recommend the use of pressure equipment to clean roof tiles”

      Tom, you have left several comments on this website, some quite agressive in nature, in many of them you have told me to keep my opinions to myself. You should know that I will continue to highlight the damage high powered pressure washing can cause to roof tiles, just as I will continue to highlight the widespread miss-selling that has become rampant within the roof coating industry which you work.

      Neither you or anyone else with a vested interest will be able to stop me from sharing my opinions on my website.

  15. TomFebruary 15, 2014 at 11:36 #

    Haha what a load of tosh! It’s only a worldwide trade. The coating applied is the same that is applied during manufacturing the tile! I’m a professional roof coater in the commercial sector and I know for a fact my knowledge on this subject far outweighs your opinions.

  16. TomFebruary 15, 2014 at 11:46 #

    To ensure the life of a fibre cement roof or fix a leak, it would require pressure washing to remove the dirt and moss then apply a protective coating. This is the industry standard. As I’m sure you don’t know, fibre cement roof sheets are much softer that a slab of solid compressed cement (a roof tile), yet it is fine to pressure wash these. Very strange. Also it depends on the nozzle and water flow whether or not a low pressure wash works. 15 liters per minute at 100 bar with a turbo nozzle would suffice. You have to have 500 bar plus to damage compressed cement. But you wouldn’t know this as you have no experience in the industry. My business is booming, even with this website going so I’m not worried. I carry out roofing, cladding, cladding coating and much more. Pressure washing may take 10 microns of the tile away when cleaning. Two coats of roof a good quality roof coating will add 30 microns thickness to the tile. Please let me know if it gets to technical for you. Your just an armature DIYer at best.

  17. TomFebruary 15, 2014 at 13:54 #

    Another gripe. Your gallery comprises of roof coating jobs where the moss has grown back? Shock horror, it grows back eventually! Those streaks look exactly the same as streaks on newly laid tiles. The paint flaking on the ridge line is where someone has re pointed the ridges and hasn’t left it to dry out enough before applying the coating. The coating has soaked into the cement and killed it. The red roof coating is a complete bodge! The sand coating 07872672457 away and is completely gone after 15 years. All that’s left is a bare cement tile with no protection nor colour coating. So I don’t understand where your argument that the pressure removes the sand coating? It’s already weathered away. Also you mention about breaking tiles?? All broken tiles are replaced during cleaning and coating. All ridges re bedded, never pointed as the muck will just fall back out after a frost. I invite you to my next job. You can watch my work stage by stage. But I know you will not as I will prove you wrong.

  18. Paul SwainsonFebruary 16, 2014 at 21:16 #

    Hi, I was interested to read your article about roof cleaning & what the tile manufacturers say. If I am correct in what I have read from Marley/Forticrete etc. they do not recommend walking on the tiles as this may cause damage to them, but you have stated in your article that you recommend cleaning using a scraper & a hand brush. Please could you explain to me & all of the other people that read the information on this site, how you manage to use a hand brush without walking on the roof tiles, or perhaps you use it on the end of a pole from the gutter level? I have only just come across your site whilst searching for roof cleaning & have not yet had a chance to open every link, but once I have I am sure that I will have lots of other queries. looking forward to hearing from you & trusting that you post your response. Many thanks. Paul

  19. AdminFebruary 17, 2014 at 09:05 #

    The advice I have received from several tile manufacturers has been clear. Foot traffic on roof tiles should be avoided whenever possible. Moss growth will not cause a problem to most roofs but if it prevents water run off or gutter blockages then it could be removed, pressure washers are not recommended by either Marley or Forticrete.

    I have yet to come across a single tile manufacturer that recommended the process Prothos uses, that is cleaning the tiles and spraying them with paint for aesthetic purposes.

    Three tile manufacturers have told me that pressure washing a roof will invalidate the guarantee they offer.

    Does Prothos inform its customers of this before carrying out any work? I cannot see any information about this on your site?

  20. TomFebruary 17, 2014 at 11:08 #


    The tile guarantee is valid for 50 years. Most roofs we clean are over that age. Also I would be interested in some statistics from the tile manufacturers of how often they actually uphold any guarantee and pay out?? Very few I suspect. From out reviews you can clearly see we have never damaged any customers tiles. I will be asking the tile manufacturers for their independent research results for the damage caused by pressure washing. Again, I doubt they have done any! All your articles from councils and trading standards were published as a direct result of cowboy companys with the wrong equipment, no experience and no morals damaging the tiles. The pressure washer done no damage, the idiots with no clue of the correct way to use one did. You are correct in being extremely annoyed with the huge amount of poor quality work being carried out in the sector but there are many companies doing a great job. We have heard of cowboy companies using normal dulux paint on a roof! That’s what gives this trade a bad name. When I have time I will post a video on YouTube of me pressure washing some new tiles at 250 bar to prove that only tiny specks of sand come off. Scraping also takes small amounts off. I know this as we have done both methods. Why would a manufacturer recommend you clean and coat your tiles?? They are loosing business hand over fist as many many people are cleaning rather than re roofing. In summary, till I have scientific studies in front of me, I and many others will just see this website as a board with speculation and opinions. Not prooven facts. And when I say prooven facts i don’t mean and article by a council because of a cowboy trader.

  21. AdminFebruary 17, 2014 at 11:49 #

    Hi Tom,

    I am happy for you and others to view this site as a board of speculation and opinions. If you and others wish to ignore the current advice from Trading Standards, tile manufacturers, NFRC, councils and consumor protection organizations then that is entirely fine by me.

    Unlike many roof coating companies, I have allowed comments to be made on this website so people such as yourself can share your opinions and experiences. I have not edited or deleted any comments, even if I disagree with them.

    You should know that this site wasn’t directly targeted at you or the business you manage with your father. There are many other businesses within your industry making totally outragaous claims about roof coatings, from increasing house value by 10% to reducing heating bills up to 27% ( + many more) all the way through to increasing the life of the roof by 25 years or how moss causes roofs to “cave-in”. If this website shines a light on some of those questionable claims then I am happy. There will always be conflicting information but I have provided links to the resources I could find to disprove many of the more outrgaoues claims.

    You and I obviously have a difference of opinion regarding roof cleaning and the application of coatings. But this is just one site offering opinions from many different sources. There are many more sites promoting roof cleaning/coatings so currently anyone researching this topic can find a variety of opinions and make up their own mind.

    Since I launched this website I have already noticed a significant reduction in the number of websites stating that a roof coating can reduce heating bills. Many of the sites that were making such claims are no longer doing so and i put that down to the huge exposure that this website has.

    I stand by my comments on this site but I do agree with you, more scientific studies are needed.

  22. TomFebruary 17, 2014 at 14:26 #

    I’m glad you have also picked up on these barmy claims! Many times I have emailed these companies telling them that their claims are false and very miss leading. There is a company called ….thermalroofcoating! I haven’t included the first part. How can paint insulate! And why would anyone think of painting the roof when looking to save energy. It’s plain mad.

    As you are interested in providing a impartial and unbiased service I invite you to come to one of our cleaning and coating jobs and report your findings to this website. At the moment this website looks as if you are promoting a service which you provide (Moss go).

    Why is the owner of this websites url hidden? Mine is easily accessible on the web. I’ve nothing to hide.

    I would like to add our website has a blog with a comment facility. If you look on our blog you will see we have already, briefly touched on the subject of thermilate roof coating and how it is nonsence. The reason why I insist on coming to this site is because you claim that pressure washing damages tiles, but have not factual proof for the claims. Yet you make out that it’s industry knowledge and will destroy your tiles. Should we not pressure wash our patios and instead re lay it every two years? Surely pressure washing must lessen the life of a patio too?