Lichen removal from roof

[The Natural Philosopher]

Can with a pressure washer.

[The Natural Philosopher]

Pressure washing does the trick.

Ive got some on a stone patio that looks like I slaughtered someone and let the blood dry. Its bright crimson. Got it all off, and bugger me it rained and there it was again..

[Peter Crosland]

Do you actually mean lichen? I suspect you are troubled by the ball shaped growth of moss which is quite a different thing.

Peter Crosland

[Phil L]

from close range, but not from a ladder at gutter height.

[marvelus]

This is a myth.

[Andrew Mawson]

Oh no it isn't !!!!!!!!

AWEM

[Nick H]

Why would you want to "clean" your roof and make it look like it wen up 5 minutes ago ? I had a flyer through the door the other da offering to clean and seal my roof before all manner of terrible thing happened, all caused by the s**t and crud thats been up there quit happily for the last 50 years. It really is a load of bo**ocks, totally "invented" problem which preys on the fears of the less wel informed, I personally know of one older chap who paid three and a hal grand to have his roof "cleaned and triple sealed" whatever the hel that is supposed to mean, all because he was led to believe that hi roof was being destroyed by the moss and dirt on it. This is a totall invented problem so dont get suckered in

-- Nick H

[Andrew Gabriel]

Nope. There was a brilliant example next door to my grand parents. Their bare phone wires passed over the roof of next door bungalow. There was a very straight line across the roof some ~5' under the phone wires were any drips would land. From that line all the way down the the gutter, the roof was completely clear of moss and lichen. Above that line, it was covered in both. That was the first time I noticed the effect, long before I ever read or heard about it anywhere else.

[Matt]

As do the walls of the council offices when you piss off the local farmer.

[Andrew Gabriel]

I recall a whole village being done, when the farmer had forgotten to switch off the muck spreader as he drove it back through the village to the farm buildings.

[Mary Fisher]

A build-up of mosses and deposited dirt can be a problem on a flat roof where it can't get washed down by rain. We had such a one on the school which I (with others!) governed, it cost us a lot of money.

I agree with everything else you said, if it's on a sloping roof.

Mary

[Andrew Gabriel]

What harm did it do? My parents have a wonderful moss growth on a flat roof, underneath a tall TV aerial where it gets fed with copious quantities of pigeon poo.

[Mary Fisher]

The roof, while nominally flat, became uneven. Water puddled and because of the moss didn't dry quickly, in colder months not at all.

Moss invaded the seams (I think overlapped rather than butted) and there was gradual water ingress to the layers beneath. Round the 'bubble' rooflights it was much worse..

That's it put very simply, The surveyors' reports ran to very many pages. The complications meant re-roofing - with a slope for peace of mind :-)

It was probably badly built in the first place, it was only about fifteen years old when the ceilings showed damp. The old, Victorian, brick built and slated roofed school had none of those problems but it wasn't large enough when it (a Junior) school had to take in children up to 13. The new building was forced on us, we didn't want it.

The theory that flat roofs don't hold water is good. The actuality is often different. Moss will grow, it can roll off sloping roofs and block gutters but that's the worst harm, I suspect. There's nowhere for it to roll on a flat roof, it simply builds up, layer on layer.

Mary

[Andrew Gabriel]

This sounds like the support underneath collapsed, which I doubt you can blame on the moss. Strawboard was commonly used from the 1960's through to the 1980's. A cold night causes condensation to form on the back of the felt, which then rots the strawboard causing dips and puddles to form. Initially the roof stays waterproof, but eventually the felt fails due to stretching.

[Mary Fisher]

It wasn't the support.

But there's no point in holding a post mortem so far away in time and space. It was done at the time and the problem rectified. The school is still fine, an 11 yo grandchild was the latest in the family to enjoy its facilities.

Mary

[marvelus]

There is no evidence to support this nonsence. If you have any other than some unsuported anecdote please share it. Otherwise there is no way some insignificant dilutions of copper salts, which would be washed away by the same rain thats supposed to be spreading them, could act as a weed killer. The same sort of people who believe in this probably also believe in homeopathy. Maybe your auntys neigbours friends mother has a rabits foot tied to the tv ariel to kill the moss.

[The Natural Philosopher]

You can see copper staining near to any copper metal thats exposed to sun air and rain.

You can see copper plated rooves that never seem to have lichen on them.

Copper has long been known to inhibit shellfish and seaweed encrustations.

Not conclusive proof of this, but it does indeed show that copper salts do NOT wash away. And that copper itself, and salts thereof probably are efficient anti-(some kinds of life at least) agents.

I wouldn't be too quiock to condemn.

Actually, since I have a lichen problem I';ll throw some copper on it and see what happens.

[Andrew Mawson]

copper wire

parents.

bungalow.

neigbours

encrustations.

Some antifouling for boats is copper based to inhibit growths - see:

[djc]

Normal for wooden ships in C18 the origin of the phrase "a copper bottomed investment"

[Steve Firth]

Not for long if EU directives on biocides are implemented.