Moss on the Roof

[Anonymous]

I have a late Georgian/early Victorian (it has been messed about with over the years!) house. The roof is not original, and sometime in the past concrete slates/tiles have been used during a re-roofing. They look fine, but I am slightly concerned at the amount of moss that seems to be growing along the ridges. The roof is quite high, and access is not easy. Anyone have any tips on how to best go about removing the moss (or indeed if I even need to bother).

Regards

Sam

 

[Anonymous]

My experience is limited but I once had dealings with an early artificial slate roof. You know, those horrible shiny things that look nothing like slate.
Anyway these particular 'slates' had become so porous that they were supporting a veritable jungle of moss. Personally I have never come across concrete tiles that have become that porous.
The classic solution to moss is to string copper wires across the roof. Apparently the rain reacts with the copper and whatever runs down is not good for moss etc. Mike.

 

[Anonymous]

There are chemical means - the most effective biocide for moss is dialkyl dimethyl Ammonium Chloride, which you can get in various proprietary formulations. the best known is Lichenite, which is expensive for five litres of a 2 per cent solution. There are cheaper alternatives available from companies who specialise in sports ground maintenance and golf course management - there's one called Qualgex from Rigby & Taylor which works out at around the same price for a 9 per cent dilution.
Apply it on a still, overcast day with a spray and leave for 72 hours before brushing off the growth with a stiff-bristled brush.

 

[Anonymous]

My mother's house roof has the same thing and it doesn't seem to cause any problems with the roof (i.e. no damage or water ingress) - except that birds love to root about in the bigger humps, which means that lumps roll down into the gutters and can accumulate there or in any traps at the bottom of down pipes etc. If access is a problem because of the height of the roof, I'd say just leave it - the moss on my mother's place has been there 20 years at least (small concrete tiles) without any problems resulting at all. Incidentally some blokes were going round the area offering to remove it by pressure washing. It's only a bungalow but they concocted a story about how it was essential to remove it and said they'd do it for around a thousand quid! Apparently they did half a dozen bungalows in a couple of days - it seems to be an alternative to the old "we have some tarmac left over do you want your drive done" scam. Buy a cheap pressure washer, use their electricity and water and make a pile of money in a few hours!

 

[Anonymous]

I have a pressure washer... and I'm skint... are there really such mugs about? <IMG SRC="http://www.periodproperty.co.uk/discussing/smileys/smile.gif" BORDER=0 ALT="">

We have moss everywhere - we live in a wet place - and have found that pressure washing makes little difference - it simply comes back again.

 

[Anonymous]

As long as there are no deep rooting plants and it is only lichen and moss, leave well alone - just keep gullies and gutters clear of debris.

Bryan

 

[Anonymous]

I've heard of the coopper wire approach to tackle moss on a thatched roof. If you do go down this route though, bear in mind that that the run off may kill any other plants at ground level under the eaves.

 

[Anonymous]

We have a patio that is in the shade apart from early morning, over the winter and early spring we get a growth of moss etc. making it very slippery, early this year i was talking to the expert at the local garden centre and he suggested Armillatox which cleared the original growth and has kept it clear for about nine months. Not quite sure how you would apply it to a roof though.



http://http://www.armillatox.com/

 

[Anonymous]

A ladder and a pressure-sprayer, perhaps?
As soon as we're guaranteed a dry spell I'm going to try it on an outhouse roof and the lethally slippery paving in our back yard.

 

[Anonymous]

Funny thing was Moo that the reason I had spoken to him was for advice on Honey fungus on a tree and this stuff was the 'only' thing that would kill it didn't touch it seemed to grow even more afterwards. The moss/slime thing was only an extra use but it worked for that.

David.

 

[Anonymous]

Thanks for all yr advice. I think I will take the zero effort approach...and just ensure the gutters are ok.

 

[Anonymous]

I was hoping you'd respond to this one, Bryan - thanks for your comments. I've never known whether to worry about roof moss or not.

 

[Anonymous]

That's okay David; it is nice to be of some help with the ‘moss on roofs’ query.

It is easy to look on these small, seemingly insignificant things, like moss on a roof, as of no particular need for concern - that is until people start to look a lot closer at things.

It is quite safe to say that common lichens and mosses will do no particular harm to a mineral roof, if for instance a stone roof is delaminating then frost and ice will do a lot more harm than say moss. Whereas root and leaf growing plant life can be utterly destructive. In fact in most cases, a ‘weathered’ roof can look much more in keeping with the environment than a sparkling clean one (anyway, it adds to the insulation!).

But sure, pluck out anything with roots and stalks and leaves as they could wreck a good roof.

On the other hand! Traditionally built roofs are not ‘patios’ or ‘concrete driveways’! They are constructed entirely differently, with a varying range of different materials, in an entirely different manner. Acidic, type weed killers and perhaps other types of cleaning agent could well adversely affect some parts of a roof in the longer term, i.e., leadwork, fixings, underfelt, woodwork, surface finishes, etc. However, much more importantly, inexperienced ‘pressure washing’ is far more likely to do an awful lot more damage in the short term! (I am sure a commercial outfit would justify any costly damage as: “a fault waiting to happen” and “aren’t you fortunate we have found it”!)

As an experienced Slater & Tiler I would not normally even consider, ‘pressure washing’ a roof, period – only under ‘extreme’ circumstances and then selectively under low-pressure, and with a great deal of caution and know-how.

Thanks for inspiring this further thought on the subject David, it could hopefully put someone off of pocking their heads over the parapet and pressure hosing their roofs off.

Bryan

 

[Anonymous]

I must say, Bryan, that the idea of pressure washing a roof also fills me with horror. Particularly when you consider that roofs are designed to withstand falling water - not water being squirted UPWARDS at them (which I'm prepared to bet is the way that most pressure roof washing would be done)!