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Is moss harmful to roofs?

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  • diystarter7
    diystarter7 Posts: 5,202 Forumite
    1,000 Posts First Anniversary Name Dropper
    Section62 said:
    MoreProbs said:
    I've no idea, so asking - what would happen if you used a moss killer? Would it die off and erode away, or would the deed stuff remain?
    If possible, clean it off every so often as it keeps hold of water/rain for longer and cycle repats itself and over the years could cause an early deterioration in the felt than otherwise would have happened.



    Or is that just one of the horror stories put about by roof cleaning companies?
    What "stories"?
  • Apodemus
    Apodemus Posts: 3,410 Forumite
    Ninth Anniversary 1,000 Posts Name Dropper Combo Breaker
    Nobody has mentioned that the place of moss in the environment is to act as a primary coloniser.  Once it takes hold, it provides a medium where other plants can germinate and before too long, you have a whole ecosystem up and running on your roof.  That's great if you are going for a green roof, less so if the roots start forcing their way between layers of roofing felt, tiles, slates, flashing etc. 

    If you add a layer of "shingle" to the mix, you help the mosses by improving the moisture retention of the substrate and provide a better medium for the secondary colonisers in the system.  Again, this is no problem if the roof is designed to cope with it, but issues can arise if this is on an ageing felt roof.  
  • twopenny
    twopenny Posts: 7,539 Forumite
    Part of the Furniture 1,000 Posts Name Dropper Photogenic
    The moss grows on north facing mostly.
    We have now insulated the roof space and got rid of open fires that warmed the roof space somewhat giving ideal conditions for moss to grow.

    You can clean it off but it will re seed and grow again so get a practice of how to do it regularly.
    Personally I got a bit anxious over this with old clay rose tiles suddenly growing moss but it was an eternal effort and I've not known it do any damage. The moss dries out in summer.

    A flat roof is different. More fragile environment if it's shaded and holding water. It shouldn't be holding water if on properly. That may be the thing to look into.

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  • diystarter7
    diystarter7 Posts: 5,202 Forumite
    1,000 Posts First Anniversary Name Dropper
    twopenny said:
    The moss grows on north facing mostly.
    We have now insulated the roof space and got rid of open fires that warmed the roof space somewhat giving ideal conditions for moss to grow.

    You can clean it off but it will re seed and grow again so get a practice of how to do it regularly.
    Personally I got a bit anxious over this with old clay rose tiles suddenly growing moss but it was an eternal effort and I've not known it do any damage. The moss dries out in summer.

    A flat roof is different. More fragile environment if it's shaded and holding water. It shouldn't be holding water if on properly. That may be the thing to look into.
    Hi

    Thanks for that and we have had a property we bought that was full of the stuff it was a bungalow, the north face was covered as tall tress also close by causing shade

    The house we live in had a small section of flat roof, looked go we don't get surveys done as not worth the paper they are written on on most properties unless property is vast and you see/fear movement, dry rot etc.. Having bought the house and the flat roof was nort facing, before we had major works to it i went up and checked. Where the moss have gathered near a curve it was a good 15/20 mm thick - that part of the roof rarely gets the sun. The rest of the roof looked very good - i removed the moss carefully but over the 2/3 years of dampness/etc, when I carefully removed it I noted there were no shingles left and more importantly there was a joint in that area. We made it part of the big plan to replace all gutters, soffits/etc/etc inc the flat bit of the roof. If we had lived there before, maintenance is the key to everything and we would have cleaned it carefully or got it cleaned.


    We opted for a pitched roof that not only looks better but a lot less maintenance. We also cut the trees away that were causing a shade on that part of the house.   

    I'm not a fan of flat roofs on the whole and did not buy a property that was lovely with a massive kitchen diner extension but all of it a flat roof.

    Thanks
  • brianposter
    brianposter Posts: 1,523 Forumite
    Part of the Furniture 1,000 Posts Name Dropper
    There is no doubt that puddled water causes roofing felt to deteriorate, so it seems a reasonable inference that water retained by moss will also have an adverse effect.
  • diystarter7
    diystarter7 Posts: 5,202 Forumite
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    edited 5 December 2022 at 8:10PM
    There is no doubt that puddled water causes roofing felt to deteriorate, so it seems a reasonable inference that water retained by moss will also have an adverse effect.
    Hi

    @brianposter

    Many thanks for stating the almost obvious and as per my previous post, sincerely appreciated. 


    Thanks again

    :)




  • Section62
    Section62 Posts: 9,740 Forumite
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    There is no doubt that puddled water causes roofing felt to deteriorate, so it seems a reasonable inference that water retained by moss will also have an adverse effect.
    Yet as I pointed out earlier in the thread, it was standard practice to spread gravel over a flat roof to protect the felt and the gravel has similar water retaining properties to moss.

    UV and heat are also causes of deterioration of roofing felt.  Moss helps shield the felt from UV and the water retention, as with gravel, helps keep the felt cool.

    The question then is whether the "reasonable inference" is a fact, or a mistaken belief.

    If it were so obvious, surely it would be easy for someone to quote a reputable source... excluding the websites of roofing contractors, roof cleaning companies, and the companies selling cocktails of chemicals to kill roof moss?
  • brianposter
    brianposter Posts: 1,523 Forumite
    Part of the Furniture 1,000 Posts Name Dropper
    Section62 said:.........and the gravel has similar water retaining properties to moss.


    ????????
  • Section62
    Section62 Posts: 9,740 Forumite
    1,000 Posts Fourth Anniversary Name Dropper
    Section62 said:.........and the gravel has similar water retaining properties to moss.


    ????????
    If that was intended as a question then can I ask you to be a bit more specific please?
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