Roof moss removal

Our roof is covered in great big lumps of moss. The birds are poking around in it in the morning and it’s falling down all over the place, filling the gutters and generally becoming a nuisance. I’m constantly sweeping up great piles of it.

There are companies who remove it with high pressure water. Then there are other people who say the jetting causes more problems than it solves and that it’s best to do it manually, using a soft brush. They also suggest applying moss inhibitor to the roof afterwards.

Does anyone have any experience of this, and in particular whether it’s best to jet or to brush?


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Not sure I’d be happy with jet washing, it may possibly lift tiles/slates and also force water under them


That’s my concern. The jets point downwards, but nonetheless it seems worrying. It’s also likely to make more mess.

I used a Karcher on the front of my roof, it didn’t lift the tiles. Did it when my wife was out, obviously. Forgot to move her car off the drive. It was a right mess. :scream_cat:

Pros – Also cleans the tiles.
Cons – Mud and moss spattered everywhere.

I used a large wire brush on the back.

Pros - easy to clean up the clumps of moss.
Cons – Roof colour is now patchy. Clean areas and dirty areas.

Do you have a lot of overhanging trees over your roof ? We have found cutting back any that have done so reduces moss build up.

  1. Spray/cover the moss with a hose pipe.
  2. Scrape off the moss in stages, with a soft bristled brush.
  3. Apply moss remover.
  4. After 24 hours clean tiles/remove dead moss with hosepipe.

This worked on my roof. Do NOT use a pressure washer and do not do the above if there’s any risk of the temperature being below zero, as this may cause unnecessary tile damage.

I guess the key is how pitched/accessible the offending area is. And, how “handy” a man you are - this will determine whether you do it yourself or get a man in.

We have the same problem, on concrete roof tiles, 50-odd years old now, with quite rough surface. No trees close, but it is a straight ridge roof with gable ends, sides facing south east and north west. Latter is worst as most limited sun. I’ve contemplated jetwash, but certainly would not do from below, and it would be challenging to go up to the ridge to do, even though only a chalet bungalow.

I understand one can engage professionals to remove the moss, but unlikely to be cheap, and likely will need doing every maybe 2-3 years or not worth bothering. Impregnating with chemical mosskillers might ensure longer resistance, if that is possible, and if not environmentally harmful given that roof drainage goes to surface water drains. The only permanent solution is probably re-tiling, with smooth surfaced tiles, which may last 20-30 years or more before surface degradation starts to give moss a key to adhere.

Those are my thoughts - it would indeed be interesting to learn of other people’s experiences.

Or woman!


I have a north facing roof elevation which is shallow pitch, with larger interlocking tiles (which means plenty for moss to grab on to). I would never advocate pressure washing, for numerous reasons, the primary one being that it can abrade the surface of the tiles, especially elderly concrete-type ones. Be careful to check moss killer instructions, as some of the iron-based ones can stain slabs. Personally, I’m not a fan of using chemicals which will easily find their way in to a drain - although I do use lawn treatments in very modest amounts.

If reachable, I would use a wallpaper scraper, perhaps taped to a broom handle, and then sweep the released moss down.

My roofer man cleaned mine out with a small trowel a couple of years back and the moss hasn’t returned yet. It filled ~ 1/4 of a wheelie bin!

In a previous house we had a small north-facing extension that used to get covered with moss. I laid a line of thick (2 - 3 mm.) copper wire along either side of the ridge. Rainwater reacted with the copper to form (I believe) a weak salt solution, which took care of the moss in a matter of weeks. Worth a try, though I’m not sure how much copper you’d need on a full-sized roof, and if there might be any side effects.

I’d try a “wet and forget” type spray that is a solution you mix with water and spray over the roof when the weather is dry. It will slowly kill the moss and wash off with rain over a few months.

IMHO brush without question. I’m assuming you have concrete tiles rather than slate HH?
As you may know, the former have a sand finish which any vigorous - wire brush rather than stiff brush - may disturb, which over time will begin to destroy the surface, potentially weakening the tiles; scrapper for any stubborn parts.
Best to remove in dry weather, when the moss is not spongey and it will remove easily. It just takes time to do a roof. When done, block the downpipe and then hose or jet wash, just the guttering and clean out, before unblocking the downpipe or use a suitable vac.
I had mine cleaned last year (again) by a chap who did it all by hand, but he does have a serious industrial vac, to clear up. Did a good job and he does travel.
I’ve been associated with building trade for a long time, so I have seen lots. The copper wire is a trick often used on church roofs. I have tried, but wire has to be strong enough to be strung, which means it becomes strong enough to support birds, which creates a different issue. Fixing is another issue, trying to isolate the steel fixings from the copper! No experience with spraying the roof after cleaning. Moss on a roof, attracts more growth, so fairly regular brushing around two or three times a decade will hopefully keep it at bay. I checked mine the other day, only that closest to the tree has some small regrowth, the remainder all clear.
Two thoughts to bear in mind, unless you have a very light weight contractor, no roof walking - they are not designed for walking on; a good roof ladder will be fine. The other is the age of the tiles. These do eventually go porous, holding moisture for longer, which can attract moss - if they were reasonable quality when new, life should be >50 years, but IIRC you are by the coast, which will have some bearing.
A surveyor or a trust worthy roof contractor, can easily confirm if your roof tiles remain sound. It is unlikely to be the cause of heavy moss. Is your roof two sides pitched one to a central ridge or a hip roof (meets in the middle)? Is each roof elevation similarly affected?

Hope that helps, SH

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Be very careful. At my gaff in France the previous owner used a chemical treatment and it has destroyed the integrity of the tiles - they are flaking away. Fortunately it is just on one section of the roof.

The problem with moss is it has micro roots and spores that find their way into the smallest holes in the tiles and then it becomes integral with the tile.

Agree – and one thing I noticed with my larger Marley Modern concrete tiles is that the overlapping gutters can get blocked and dammed by the moss = water trickle ingression (just where the underfelt had been compromised!). This is another reason not to jet wash.

Concrete overlapping tiles (with the overlapping side gutter joints) are also prone to breaking, which cannot be detected unless you lift them a tad - ergo the use of my roofer man and his knowledge of how to walk on a roof. I think he replaced ~10 tiles of the 600 due to ‘invisible from the ground’ gutter/overlap breakage. £250 well spent in my book given the potential consequences.

Our roof is pretty old and has various patches of moss. We got a local specialist company in to give us a quote. The converstaion I had with the owner put me right off the whole thing. He said they used a bleach-based solution. When I expressed some concern about possible long-term damage to the tiles he told me that they apply the solution to a small area first and leave for a few days. If all seems well they then proceed with the entire roof.

I wasn’t happy. Firstly, a few days is hardly long enough to evidence any long-term effects. Secondly, his assertion that they only proceed ‘if all seems well’ sounded to me a bit wishy-washy and highly subjective, and the assessment is being carried out by the people that want the money!

I politely declined. Unless causing major issues leave well alone.

Thanks everyone, that’s so helpful. My house is exactly like @Innocent_Bystander ’s, with concrete tiles and south east / north west orientation. It’s a two storey house and I don’t like going up ladders, so I’d definitely need someone in.

There is a local person, Moss Doctor, who does it by hand and then uses chemicals. I really don’t like the idea of the latter, and we haven’t used chemicals on the garden for many years. So I’m in two minds; get someone to clean the roof using roof ladders, but not to use chemicals, or leave the moss in place and get someone to just clean out the gutters, and possibly remove any big loose lumps at the same time. As so much has come off already, maybe the birds have done quite a lot of the work.

i had our roof moss removed by a company using high pressure water.
all as i know my water bill was very high. i read that if you do not have it removed
it can cause a lot of damage to the roof

My situation may be different as my roof is made of clay tiles. However, on the north facing side of the pitched roof I get a lot of moss. I asked a builder who was doing some other work a few years ago about removing it and he said that it would do more damage to the roof than any good. I just continue to gather the moss up - it can be very messy when wet.

Thanks. I do wonder if those who say the miss can do damage are those with an interest in charging for its removal. I’ve read that it can trap water and cause problems when it freezes in winter. You certainly don’t see lots of people running around on roofs removing moss, so maybe it’s not such an issue. I don’t want to spend hundreds on having it removed if it will return in a year or two and need doing again. We have been here since 1992 and have never had it done, but this is the first year we have had a deluge of moss all over the patio, with big lumps 10cm square. Maybe now is the time to do it.

It’s climate change - the moss is taking over! Seriously, is the moss worse because it is getting more established and needs dealing with, or have the weather conditions over that last 18 months encouraged its growth? Maybe if the weather pattern changes it will reduce again.