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View Full Version : How to remove mould from rooftop?



Renmoo
22-08-2006, 12:25 AM
Dear all, my house's rooftop has been gathering a lot of patches of green mould and they are unwashable by rain. What is the best way to remove those ugly patches? I believe the idea of using jet-sprayed water would pop into most people's mind, but does it really work? My dad thinks that it is quite dangerous to climb up the roof and clean it using scrubs (I know... I know..., but we are not used to climbing up the roof as if we are on the ground). Perhaps he should hire a contractor to do it instead? Thanks for any feedbacks.

Cheers :)

Tux
22-08-2006, 01:27 AM
Dear all, my house's rooftop has been gathering a lot of patches of green mould and they are unwashable by rain. What is the best way to remove those ugly patches? I believe the idea of using jet-sprayed water would pop into most people's mind, but does it really work? My dad thinks that it is quite dangerous to climb up the roof and clean it using scrubs (I know... I know..., but we are not used to climbing up the roof as if we are on the ground). Perhaps he should hire a contractor to do it instead? Thanks for any feedbacks.

Cheers :)
use wet and forget or 30 seconds

Rob99
22-08-2006, 01:52 AM
If its iron, maybe you could pull the nails and flip it over!

Morgenmuffel
22-08-2006, 07:23 AM
Rob is of course joking

If it is Iron, then a stiff broom and soapy water should do the trick, but you have to be careful the mold/lichen doesn't end blocking your guttering

If it is a tile roof, it may pay to get a contractor in, as you could end up with leaks if you are not ultra careful

Cicero
22-08-2006, 07:50 AM
Hire a good water blaster.

Strommer
22-08-2006, 08:00 AM
Hire a good water blaster.

Yes. Falling off roofs causes many serious accidents and even death. I have water blasted our roof prior to painting and need to do so again this year but this time I will use a safety rope.

BTW, if you plan to use a water blaster to remove mould moss or lichen from any surface, do not waste your time with the cheap sprayers now available - get a proper high pressure unit from a hire centre.

somebody
22-08-2006, 08:16 AM
We had our tile roof professionally sprayed, cleaned and sealed a few years back by a contractor (Edwards & Hardy Roofing or something along those lines). They first sprayed with the chemical to kill the lichen etc. properly - and then left it for 6 months to work. They said that the "fast acting" chemicals like 30seconds etc. cause damage to the tiles, and wouldn't kill the lichen at the roots properly - so you'd end up re-spraying every year or so. You could actually see the lichen changing colour, and eventually falling off by itself. They came back in 6 months time to wash it thoroughly - no waterblasting because that can damage old tiles, and re-mortar bits which needed it, replaced broken tiles etc. They then sprayed it with some sort of preservative type chemical to "protect" it, and came back 3 weeks later to spray with a silicon sealer or something along those lines. It worked brilliantly - the roof is spotless now, and has been for years.

I would really leave it up to the professionals - it's not too expensive to have done (if I recall correctly, it cost about $700 all up for a 3 bedroom house + garage), and you pay in parts for the work which they have done so far.

bonzo29
22-08-2006, 09:54 AM
Agree with somebody, professionals are the best and safest.

However if the cost is too much for you the quaternary ammonium based compond cleaners made by Ecotect etc from Mitre 10 etc are safe from the chemical angle.
The do take a while to act( afew weeks but are effective.

Never but never use rhe 30 second sodium hypochlorite bleaches

Trev
22-08-2006, 10:07 AM
click here (http://www.edwardsandhardy.co.nz/) I have had my tile roof done by Edwards and Hardy as well. They come back every 2 years or so and spray on a preventative.

Trevor :)

pctek
22-08-2006, 04:35 PM
Hmmmm. My son just mailed me 24 500ml cans of Sika -W715. This is apparently a mould, lichen and algae remover suitable for roofs, metal, stone, concrete, painted and unpainted wood etc etc.

Spray, paint or sponge on, leave for a bit and hose off.

And I don't have a mould, lichen or algae problem....

somebody
22-08-2006, 07:09 PM
I have also used another product (not on a roof though - for mildew in concrete paths etc) called "Move It". It was supposed to be one of those slow release, "safe" products - it worked quite well, but took several months for the stuff to actually be killed off.

John W
22-08-2006, 09:46 PM
Just like "somebody" we had our roof moss sprayed then 12mths later sealed by Edwards & Hardy in Dunedin. Took the moss a good 12mths to curl up and get blown off the roof.

After 18 mths & $700 the roof looks like new, highly recommend them. Except the fellow that did the job, no safety restraint of any sort, on a roof with 35-40 degree pitch and up to 3 stories high!

Renmoo
22-08-2006, 10:00 PM
Thank you very much to all of you who have contributed to this thread.

My dad in fact is thinking of hiring a contractor to do the cleaning job since it is pretty dangerous for him to roam around the rooftop without any safety measures - he'd rather be safe than sorry. I will check out http://www.edwardsandhardy.co.nz/ as well, meanwhile.

Cheers :)

roddy_boy
23-08-2006, 01:46 AM
I had to get rid of this crap from my parents roof. Just used a water blaster. Only fell off once.

Pete O'Neil
23-08-2006, 10:49 AM
I had to get rid of this crap from my parents roof. Just used a water blaster. Only fell off once.
Just borrow some kids trampoline from down the street and position it under the area your working on, with any luck if you fall off you should bounce right back up. :cool:

Graham L
23-08-2006, 01:46 PM
Just borrow some kids trampoline from down the street and position it under the area your working on, with any luck if you fall off you should bounce right back up. :cool:Even in this, there's no "perpetual motion". You can't bounce back as far as you fell. You lose energy in heating the springs and the mat of the trampoline as they stretch. :D And you have to pick the right place to fall from. Concrete isn't a good trampoline material.

Best to have a safety belt and ropes. Or get soemone else to do it.

rob_on_guitar
23-08-2006, 08:56 PM
Contractor. If they mess up they got to do it again.