Moss on roof

  the hick 13:38 12 Dec 2010

My and the neighbouring semi both have significant moss growth on the north-facing roof, which is concrete tiles. Its grown over the last 5 or 6 years, and the previous 15 years since we moved here there was hardly any. Does anyone know what can start moss growth, especially as we seem to be the only houses in the area with it? Any advice appreciated, thank you.

  peter99co 13:47 12 Dec 2010

Damper conditions due to Global Warming? Nature shows the way I think.

My garage roof has also shown an increase this last two years.

  Forum Editor 13:49 12 Dec 2010

we're becoming the victims of our drive to clean up our environment - moss on the roof is an indication of cleaner air. Less pollution means a lot more moss spores floating around, and they find an ideal home on your roof tiles.

The classic way to keep a roof moss-free is to insert narrow strips of copper into the mortar bedding of the ridge tiles. The resulting copper sulphate washes down with the rain, and kills moss before it can get started.

For existing problems you can buy proprietary moss killers. Remove all the moss, make sure your roof is cleaned of any soil deposits etc., and spray the solution onto the tiles.

Be prepared to go through the whole process again in a few years time.

  dagbladet 14:38 12 Dec 2010

Well 'the hick'. Seems you are the only house in the street affected by global warming. On the plus side you are the only one enjoying cleaner air and less pollution. Swings and roundabouts.

  Fruit Bat /\0/\ 18:47 12 Dec 2010

According to an Architect friend of mine, moss is actually good for your roof as it helps bind it all together preventing tiles from slipping or ripping loose in high winds.

Excess moss falls into the guttering and can block it, although birds will remove a lot during nesting season, therefore is a good idea to clear gutters in Autumn and Spring

  Forum Editor 19:02 12 Dec 2010

Your architect friend might want to think again.

Moss doesn't bind a roof together at all, it has exactly the opposite effect. It holds moisture that would otherwise evaporate away, increasing the weight on the roof timbers. In addition, moss root filaments penetrate into the tile substrate, exposing the roof to and increased risk of tile spalling and frost damage.

Moss suffuses oxalic acid onto the roof, and this attacks the tile surface, leading to colour loss and further weakening of the tile structure.

Very heavy moss growths will creep into the tile overlaps, and cause water to leak into the loft.

None of these symptoms will appear overnight, but leave the moss unattended and it will happen. Moss on a roof is a sign of trouble in the future, and it should be removed as soon as it's practical to do so.

  spuds 21:48 12 Dec 2010

Off subject slightly, and I appreciate moss will retain water so adding to weight and leaks etc. But the other week I was looking at an 'eco-house', which had a roof of what appeared to be soil and grass as part of its 'eco' design. I can only assume that there would be some type of drainage feature's within the design?.

Would you know FE?.

  Forum Editor 23:33 12 Dec 2010

Underneath the grass is a multi-layered roof protection. In fact these 'green roofs' are not grass, the roof will be covered with sedum plants that are small, and require minimum maintenance. The technique has been quite widely used in Germany for almost forty years.

The weight of a green roof is probably not much more than a conventional concrete tiled version, although if you're building from scratch you would probably want to increase the size of the roof timbers slightly.

The waterproof membranes that prevent moisture from entering the building are protected from their big enemy - sunlight - by the soil and plant covering,and they last for a very long time.

Micro-porous irrigation pipes are there to make sure the roof doesn't dry out in hot weather, and apart from that, and a quick going over to remove weeds and self-seeded grasses a couple of times a year the roof will maintain itself - it doesn't need mowing.

I go past the Rolls Royce car factory in the Sussex countryside quite often, and its green roof is a sight to see. It merges the huge buildings into the surrounding downland beautifully.

  Graham. 00:16 13 Dec 2010

So it's not due to bird droppings from those on the TV ariel, then?

  Forum Editor 17:19 13 Dec 2010

No, it's not.

  john bunyan 18:19 13 Dec 2010

At over 70 I spent a week on my concrete tiled roof with a wire brush to remove moss. A roofer said it was not a good idea. I was thinking along FE's lines by stripping some old copper cable and runninig a length each side of the ridge tiles, but my wife has banned me from strolling about on the roof..

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