There's something on the roof....

[Keithj]

This furry-looking growth appeared on the lime mortar joints in the roof. I don't know what it is, so I don't know if it's harmless or needs violent treatment.

Do any of the learned PPUK members recognise it? Any advice on what (if anything) to do with it?

 

[paulb33]

That's just normal roof bound licheny-mossy stuff in 'flower', isn't it?

 

[LadyArowana]

Yes, the fruiting body of whatever sort of moss it is, similar to this picture. May be worth getting rid of the moss generally as it will hold water.

 

[paulb33]

Yes, the fruiting body of whatever sort of moss it is, similar to this picture. May be worth getting rid of the moss generally as it will hold water.

There's an article somewhere that says moss on roof should be left undisturbed. It causes no harm....and removing is a folly (will just come back).

The state of my roof, I hope that's the case:

 

[MatthewC]

Yes, the fruiting body of whatever sort of moss it is, similar to this picture. May be worth getting rid of the moss generally as it will hold water.

There's an article somewhere that says moss on roof should be left undisturbed. It causes no harm....and removing is a folly (will just come back).

The state of my roof, I hope that's the case:

I reckon moss is only a problem if (a) it gets between tiles and lifts them thus causing water to track where it shouldn't, or (b) if it is so large it falls off (esp in dry summers) and then blocks gutters and drains. I think, Paul, yours might be getting near to that stage!

 

[paulb33]

I reckon moss is only a problem if (a) it gets between tiles and lifts them thus causing water to track where it shouldn't, or (b) if it is so large it falls off (esp in dry summers) and then blocks gutters and drains. I think, Paul, yours might be getting near to that stage!

Yes, you're quite right Matthew. We've big oaks that cast shadow and damp.

 

[davidbrac]

I would leave it, if you start to remove it will just come back, and in removing you can damage the mortar

 

[Keith Bowman]

I have heard that stringing bare copper wire along the ridge stops it.

 

[worms]

I would second the copper wire suggestion but I wonder if a distinction should be drawn between moss growing harmlessly on the slates, versus growing on the soft, porous surface of lime mortar?

In the latter case might it cause surface crumbling of the mortar and eventually fall off taking some of the mortar with it?

 

[Keithj]

Would a squirt of copper sulphate be a bad idea?

Copper wire I have aplenty.

 

[worms]

Hmmmm... It would certainly kill the moss, and stop you getting slugs and snails on the roof...probably get rid of a whole ecosystem including these pesky elephants that roost on the chimney pots!

 

[LadyArowana]

including these pesky elephants that roost on the chimney pots!

You aren't supposed to stick the whole elephant up there, just the feets.

http://www.1stsuppliesscot.co.uk/chimney-cowels-pots/1305-fluvent-elephants-foot-buff.html

 

[Penners]

That's just normal roof bound licheny-mossy stuff

Although I don't possess his extensive command of botanical terminology, I agree with Paul. And I certainly wouldn't worry about it, if it were on my roof (which it probably is).

 

[malcolm]

The enormous moss build up on mine (photo) backed up water under the tiles and also caused some frost damage. But we are in a very roof mossy area for some reason. If the neighbours have a massive build up of moss all over their roofs then it might be worth adding bit of copper to yours. Otherwise it's nice having a bit of green stuff - wildlife likes it.

 

[kreyszig]

what's the consensus on a bit of green stuff growing in chimneys?

 

[Penners]

That looks a bit more worrying than Keith's little bits of lichen. The ferns, etc. have obviously got their roots into the mortar joints so that, as they grow, they risk pushing the joints apart. If it were my chimbley, I would get up there with a raking tool and try to rake out as much as possible of the root systems. After that, a spot of repointing will probably be necessary. Before repointing, as a belt-and-braces exercise, I think I would soak any remaining bits of root with SBK Brushwood Killer, or something equally unfriendly.

 

[middi]

build up of moss on porous clay tiles will lead to premature failure of the tile surface. This happens during heavy frosty nights following rain, the moss will absorb and retain water as this water does not evaporate or runs off as freely as on a clear roof it will freeze resulting in lifted and delaminated tile surface. With the passing years, and especially on the north facing side of the roof, regular attention is required. Cleaning and retiling a roof is not everybody's cup of tea but our yesteryear ancestors did a lot of DIY to keep their clay tiles roofs clean of moss. When I say premature failure, instead of a well maintained tiled roof lasting 5/600 years it would last only about 1/150 years if on a north side and poorly maintained.

Don't panic, if there are no leaks live it alone. If you don't like the look of moss remove the tiles, clean the moss and be prepared to keep doing it every 20 years or so , You can apply chemical moss cleaner if you want to but I don't think anybody bothers, most of the people I know that own old buildings with clay tiles prefer to look at the moss.

Middi

 

[kreyszig]

That looks a bit more worrying than Keith's little bits of lichen. The ferns, etc. have obviously got their roots into the mortar joints so that, as they grow, they risk pushing the joints apart. If it were my chimbley, I would get up there with a raking tool and try to rake out as much as possible of the root systems. After that, a spot of repointing will probably be necessary. Before repointing, as a belt-and-braces exercise, I think I would soak any remaining bits of root with SBK Brushwood Killer, or something equally unfriendly.

That's exactly what will get done in the very near future, when my magic roofer reappears.

 

[Roger440]

So how does this copper wire idea work? Does it need to be laying along the ridge. What sort of size are we talking about?

 

[Keithj]

I'm sitting here contemplating copper wire on the roof, nitrous acid from thunderstorms and lightning, and wondering if that's enough of a dose to zonk the moss.