MegaSack DRAW - This year's winner is user - rgwb
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We have lots of moss on our roof. According to a roofer he can jetwash it off and paint the roof with a sealant to alleviate the damage done by the jetwash. I'm not so sure and according to what I read, jetwashing can damage the roof and also risk flooding, and that it's preferable to leave the moss in peace, or else scrape it off with a trowel. If anyone's had this done I'd be interested in your experience!! (and how big the bill was).
About every 10 years or so, I go up on the roof and remove much of the moss with, as you say, a trowel and a stiff brush. Takes most of a day to do ours and the neighbouring house (semi detached).
One or two places around here have had the jetwash and 'paint' treatment. In my view it looks hideously discoloured and completely, jarringly out of kilter with all the surrounding houses. No idea what the coating actually is, although I have my suspicions about oil and snakes.
Brush and scraper has to be the best way surely
National Federation of Roofing Contractors says it's all rubbish and to leave well enough alone...
https://www.nfrc.co.uk/article/2012/09/07/moss-on-your-roof-advice
I remove the big chunks then spray the roof with wet and forget once a year, works well.
We had moss on the old roof, it's a sign of good air quality apparently, as 20 years ago there was none. Since being retiled it has not reappeared. A near neighbour jetwashed and sealed, it looks bright pink to me. I just jetwash the gutters, they come up really nice with olive oil, brown pvc discoloured by uv.
A roofer told me to put small copper sheets on the top tiles. Apparently rain hits the copper and runs down preventing moss growing.
What is it that is actually bad about moss? We have York stone roof tiles -proper 35mm thick jobs. North facing roof covered in quite a build up of moss, but as far as I can tell, apart from being picked off by the jackdaws and landing on the front driveway every now and then there is no issue. Neighbour recently had two guys jet wash the whole of his roof (bid detached farmhouse) and it took two days, made a hell of a mess/racket. Couldn’t figure out why it was necessary. Perhaps vanity? Beauty in the eye of the beholder and all but I think an old property with a mossy roof looks great.
To the OP, I’d be wary of a roofer offering these services. Roofers with free time are rare as unicorn poo as far as I can tell (and hear on here.) if they’re offering this I’d be thinking ‘why are you not busy?’
Thanks everyone. You are confirming my suspicions. I think our moss will be staying!!
I scrape and brush mine off, well I've done it once in ten years. Pitch is quite low so it was easy.
I do a lot of moss removal at work, it does have a tendancy to hold moisture which long term can cause a bit of frost damage, but I'm talking very specific and localized areas. Sometimes plants like buddleia can root in it and then spread but again it's easy to spot. The main annoyance is the birds rolling it into the gutters or the conservatory roof!
We get a load falling off and blocking the gutters every few years when we get a hot dry summer. If I wanted to remove more I'd think about spraying it with moss killer and let it fall off naturally or help it with a brush.
The birds remove most of ours looking for grubs,leave well alone.
a few houses near us have had it done- a few years later and most are starting to look patchy.
sone friends neighbours had it done and the amount of overspray on their house & cars was ridiculous.
re the comment above about airflow, ISTR that the tiles are meant to “breathe” to aid ventilation and painting seals them up. Not sure if that’s the case or an excuse made up to not have it done!
You can buy stuff to spray on them.
Ours was really bad but because it’s not rained for weeks and then downpours most of it has now come off
Had to unblock all the gutters though
Don't do it! It's all nonsense, just scrape it off if you must.
Tye jet wash will potential rip through the surface of the tiles, hence why thy then spray with a clear varnish to protect it again, but that will wear off and you'll have to keep on spraying with varnish for evermore.
A friends Grandad had a knock on the door just like that, jet washed it off and had the roof sprayed with varnish, they jet washed it on a windy day which blew the sandy surface of the tiles down the road, same with the varnish, sprayed it out of big pump action bottles and sprayed it over the neighbouring cars upto 5 houses down in the wind and stuck sand to everyone's cars!
On the other hand, maybe OP hates their neighbours, in which case, do it!
Try using a moss killer spray and remove it gently with a brush.