Removing moss on felt roof

[ray]

Hello

Our kitchen extension to a 1890 terrace cottage has a felt roof. There is now a considerable amount of moss growing on the felt.

Can I remove this safely - or will this damage the felt? Should I do this by hand/with a scraper or use chemicals.

Finally should I add to the amount of small stones that should cover the roof to stop this re-occuring?

Thanks all.

Regards

ray

 

[Flyfisher]

I'm no expert but I had a similar arrangement once, as well as a flat felt garage roof, and I just removed the moss carefully by hand every few years. It never seemed to be stuck to the roof so, in my case at least, tools or chemicals were never necessary.

I believe the small, often white, stones are to provide a level of mechanical and heat protection for the felting material, by reflecting the sunlight. In my case the house was in a wooded area so this wasn't a big issue most of the time. However, the stones seemed to do nothing to keep the moss at bay.

The biggest concern I had was being careful about walking around on the roof as any large/sharp stones can be easily pressed through the felt/bitumen material. A scaffold board can be helpful in this respect or, if the area is not too large you might be able to clear the moss from a ladder using an ordinary stiff-bristled broom.

 

[Mark]

also if its a plasterboard ceiling underneath you can find that its developed cracks once you walk on it.


Or atleast thats what happened to our bathroom ceiling when I went on it.

 

[worms]

I have the same problem and it is not easy to tackle. Sweeping the moss off removes the stones protecting the surface. Picking it off may be the best option but needs greater patience than I have. Ordinary household bleach sprayed onto the surface may kill the moss but would leave the dead moss to rot into the stones and give a nice compost for bigger weeds.

The real answer is probably to get on top of the problem (sweeping and replacing the stones or picking off the moss to leave clean stones) and then keep on top of the problem by chemical means - sodium dichlorophen is great but no longer available on its own. It may still be available as lawn sand or as a spray moss treatment for paths, which I have never had much success with (it is a much weaker solution than I used to use for this purpose).

In my case the roof in question is not seen from anywhere and I guess I will leave the moss to build up again then sweep it off and replace the stones again.

 

[Lime]

The small stones on a "flat" roof are to protect the roof material from the sun.
Moss also protects the surface unless the roof is weak and/or old.
Walking on a modern felted "flat" roof is not recommended without proper walkways or some sort of protection for the surface.
Upturned carpet can used as a temporary measure made even better by a board on top.

Unfortunately the "flat" roof is not always made very well.
Often inappropriate boarding is used that softens when damp and distorts made much worse by inadequate support.

 

[chuckey]

I think that you want to spread a lot of copper bits on the roof. It is toxic to plant life. The only problem is how much and in what form? This depends on what you can get hold of for free. Underneath the copper pipes appearing through my out side walls for the taps, the wall is completely clear of lichen. I would say cut up copper pipe off-cuts into 1/2" lengths , split them and hammer them flat then put on the roof with a maximum density on the "uphill" side, so any toxic stuff that is washed off can then flow downhill and kill the moss lower down.
The white chippings ( or cheapo pebbles) are to reflect the sun as this degrades the roofing felt.
Frank

 

[Flyfisher]

Sounds similar to anti-fouling for boats so perhaps there is something similar/suitable from a chandler?

Having said that, I've never thought of moss on a flat roof as a big problem, just something that a bit of routine maintenance easily solves. A bit like clearing gutters really. Am I missing something here?

 

[Gareth Hughes]

I've never thought of moss on a flat roof as a big problem, just something that a bit of routine maintenance easily solves. A bit like clearing gutters really. Am I missing something here?

Yes, what you are missing is that most people just don't do routine maintenance any more. (Hence the attraction of "no-maintenance" plastic windows).

 

[Penners]

I think I would ask myself the basic question: which will cause more damage, the moss or the process of removing it?

If you can reach across the roof from a ladder, then lifting the moss off by hand should be pretty problem-free. But if you have to start trampling about on the roof, it might be best just to leave it alone.

 

[chuckey]

Moss damages surfaces, by first putting down little tendrils (like roots) then dieing and drying out in the sun, the area under the moss then lifts and blows away. Not catastrophic, but after 20 years or less you can see where the top surfaces of roof tiles have disappeared, this leads to a rougher surface and more moss. . . .
Best to eradicate it,
Frank

 

[Mark]

You could always concrete over it Frank.

 

[middi]

Personally I would remove the felt and do a permanent roof covering.

 

[Gervase]

I've grown very fond of corrugated iron since being in Wales. Or even the cheaty 'Onduline' stuff. It may be a bit agricultural for some tastes, though.