By Sheryl October 29 in DIY Forum
Hi, I put a new roof on 10 years ago, white tiles (concrete I think). Now quite dirty with soot and blackish mold. Mosaic Asphalt Shingle
Can people advise best way to clean these without damaging the tiles? It's a a very large 2 story house so pressure cleaning is probably the easiest approach but how to ensure not too much pressure?
Here in Norway we use chlorine to kill moss on concrete roof tiles. Chlorine is also effective against mold.
Try to use a mixture one part household bleach and 2-3 parts water and spray it on the mold when the sun isnt up. Cheap and effective, and doesnt damage concrete tiles. Be careful with the pressure washer, since the tiles might not have enough overlap to stop ingress of water.
Here in Norway we use chlorine to kill moss on concrete roof tiles. Chlorine is also effective against mold.
Try to use a mixture one part household bleach and 2-3 parts water and spray it on the mold when the sun isnt up. Cheap and effective, and doesnt damage concrete tiles. Be careful with the pressure washer, since the tiles might not have enough overlap to stop ingress of water.
thanks. I am aware of the benefit of using chlorine.
What I don't know is how to instruct the workers in use of the pressure washer so as to avoid cracking the tiles. (Distance? Are there settings? Etc)
I can't imagine that a pressure washer of normal dimensions would damage roof tiles (unless they pick it up and drop it). The only things you can change on a washer are" distance from the object being cleaned and intensity of the jet. Just tell the guys to start with an open jet (not a direct, pinpoint jet) and see how it goes. It will be difficult to ensure that no water at all will penetrate between the tiles, but that applies during heavy storms anyway.
Just sprayed our roof ,only the downstairs roof,as cannot get on the roof too
high, sprayed it with bleach mixed with washing up liquid to make it stick,
it killed the black algae/moss or whatever it is ,
Just wanting it to rain now,I should have done it weeks ago when it was raining
everyday ,next month I will be getting the house painted ,so will get the workers
to clean the 2nd story roof and also paint it too ,
I can't imagine that a pressure washer of normal dimensions would damage roof tiles (unless they pick it up and drop it). The only things you can change on a washer are" distance from the object being cleaned and intensity of the jet. Just tell the guys to start with an open jet (not a direct, pinpoint jet) and see how it goes. It will be difficult to ensure that no water at all will penetrate between the tiles, but that applies during heavy storms anyway.
Quit a bit of misinformation there.
Many pressure washers allow the pressure to be changed (mine normal one does), the cheapest one I have doesn’t (it was about 2,000) but then the pressure is lower.
All pressure washers allow jets of different widths, I have 0 degrees to 60 degrees. I also have a rotating jet head along with a foam head for vehicle washing, and a drain cleaning head.
you can get heads that allow you to add bleach to the spray, this will kill off the algae so you can then clean off the roof after that with a regular pressure wash.
What I don't know is how to instruct the workers in use of the pressure washer so as to avoid cracking the tiles. (Distance? Are there settings? Etc)
if they are experienced there is no problem, but walking on the roof can damage the tiles, this is much more likely than the pressure washer damaging them. But give them some practice on your concrete walkway first
But do be a little careful, pressure washers can clean off old paint and cut concrete, so can damage a poor condition tile.
Quit a bit of misinformation there.
Many pressure washers allow the pressure to be changed (mine normal one does), the cheapest one I have doesn’t (it was about 2,000) but then the pressure is lower.
All pressure washers allow jets of different widths, I have 0 degrees to 60 degrees. I also have a rotating jet head along with a foam head for vehicle washing, and a drain cleaning head.
you can get heads that allow you to add bleach to the spray, this will kill off the algae so you can then clean off the roof after that with a regular pressure wash.
if they are experienced there is no problem, but walking on the roof can damage the tiles, this is much more likely than the pressure washer damaging them. But give them some practice on your concrete walkway first
But do be a little careful, pressure washers can clean off old paint and cut concrete, so can damage a poor condition tile.
Thank you. Can you suggest settings for:
And a brand of washer?
My hope was that using pressure spray washer machine would remove need to walk on the tiles, is that not the case?
Can't find any workers where I live with any exprrience doing this. I have a resident handyman who will do it with 1-2 helpers So need to instruct them pretty clearly.
Thank you. Can you suggest settings for:
And a brand of washer?
It very much depends on your future use case
this will do to test the waters it will cost less than 2000 baht there are various different names on Lazada
after that we spent over 20,000 with attachments for this, the base machine is about 16,000 but then there are extras.
My hope was that using pressure spray washer machine would remove need to walk on the tiles, is that not the case?
It depends on the size of the roof and the length of hose , with our 30 metre hose it’s no problem, bit the other one is 3~5 metres so not so easy
this is the baby one
Start with a 40 degree one (white) or a 65 degree one and practice on the ground first
Also watch a few pressure washers in action on YouTube
Pressure washers are great for cleaning cement tiles, the only problem is people walking on the tiles, together with moving the machine about. You must be sure you can still get hold of the tiles you have in case of breakages.
The pressure nozzle on most DIY machines is adjusted on the actual wand nozzle, can adjust when working, so no problem.
My washer is advertised at 150 bar, as yet, never broken anything with it...😊
thanks. I am aware of the benefit of using chlorine.
What I don't know is how to instruct the workers in use of the pressure washer so as to avoid cracking the tiles. (Distance? Are there settings? Etc)
Before thinking of using a pressure washer, make sure that you have a secondary roof/membrane underneath the concrete tiles. Use a ladder and push up a tile to check whats underneath the tiles. Even if you instruct the workers to pressure spray downwards, and not upwards, water will always find a way through a tile based roof when high pressure is involved.
Chlorine isnt harmful to your garden, its actually a macro-nutrient for plants. And it has a tendency to stay inside the concrete tile and reduce future growth. Stronger chlorine mixes are better. I use pool shock and make a mix right before I spray the roof with garden sprayer. With a strong chlorine mix, there is no need to use high pressure. And you can use this trick to clean dirty walls and outside concrete floors of growth for pennies. Sometimes household bleach is left in stores for years, and will greatly lose its potency, thats why pool shock is better value. And as other people in here have said, using a wetting agent like dish soap to reduce evaporation and increase contact time is a good idea.
If roof tiles get cracked from walking on them, they are very easy to replace as long as you have spare tiles on hand from the same manufacturer. Tiles dont crack because of water pressure, but the weight of a man can split them, as they are just made in a mold from sand and cement with no reinforcement.
Can people advise best way to clean these without damaging the tiles? It's a a very large 2 story house so pressure cleaning is probably the easiest approach but how to ensure not too much pressure?
Local builders are not known for their diligence. Cleaning the roof could cause you many problems.
Before thinking of using a pressure washer, make sure that you have a secondary roof/membrane underneath the concrete tiles. Use a ladder and push up a tile to check whats underneath the tiles. Even if you instruct the workers to pressure spray downwards, and not upwards, water will always find a way through a tile based roof when high pressure is involved.
Chlorine isnt harmful to your garden, its actually a macro-nutrient for plants. And it has a tendency to stay inside the concrete tile and reduce future growth. Stronger chlorine mixes are better. I use pool shock and make a mix right before I spray the roof with garden sprayer. With a strong chlorine mix, there is no need to use high pressure. And you can use this trick to clean dirty walls and outside concrete floors of growth for pennies. Sometimes household bleach is left in stores for years, and will greatly lose its potency, thats why pool shock is better value. And as other people in here have said, using a wetting agent like dish soap to reduce evaporation and increase contact time is a good idea.
If roof tiles get cracked from walking on them, they are very easy to replace as long as you have spare tiles on hand from the same manufacturer. Tiles dont crack because of water pressure, but the weight of a man can split them, as they are just made in a mold from sand and cement with no reinforcement.
Unfortunately there is no secondary roof or membrane.
Unfortunately there is no secondary roof or membrane.
Are hiring a contractor or just using local guys?
Do the have the washer, or are you going buy one?
Most cheap washers do not have enough pressure to hurt the tiles, if they are being sprayed down on. As others have said, people walking on could cause damage.
Unfortunately there is no secondary roof or membrane.
As you see this video, a tropical typhoon can imtate the effect of a pressure washer. The tiles in this video didnt have enough overlap and enough pitch. But even a properly laid tiled roof wont be able to stop the water from coming in if someone shoots water horisontally, or even worse, upwards against the overlapping tiles. What I would do in your situation is to use a chlorine solution in a low pressure sprayer with some dish soap. There are also ready mixed anti mold mixes in 4-liter bottles with a nozzle in my country that you attatch to a gardening hose that can easily reach 10-20 meters. If you are not comfortable standing in a ladder with a low pressure spraying system, maybe rent a lift and spray the roof yourself? And if you use high pressure instead of chemicals from a lift, some water leakage through the roof a hour or so will dry up and probably not damage your home.
Are hiring a contractor or just using local guys?
Do the have the washer, or are you going buy one?
Most cheap washers do not have enough pressure to hurt the tiles, if they are being sprayed down on. As others have said, people walking on could cause damage.
Local guys, I would prefer an experienced contractor but none available out here.
Will have to buy the washer. I'll try to get as long a hose as is affordable to minimize need to walk on tiles.
Local guys, I would prefer an experienced contractor but none available out here.
Will have to buy the washer. I'll try to get as long a hode as is affordable to minimize need to walk in tiles.
Make sure you have a decent, long, clean feed hose, and good pressure/volume of water to feed it.
I think you will likely have one guy carrying the washer on the ridge of the roof, and one guy handling the spray wand, so an extra long high pressure hose would not be required.
I would pre-spray the roof with whatever chemical cleaner you like with a garden sprayer, let it soak and pressure wash it off from the ridge down. A push-broom can help also.
All that said, i would not send a crew up on a roof the is not leaking. You probably are not going to like the result, and even if you do, it may not last long.
I would pre-spray the roof with whatever chemical cleaner you like with a garden sprayer, let it soak and pressure wash it off from the ridge down. A push-broom can help also.
That is exactly the wrong order of cleaning.
You should do the first pass with water to get as much dirt and debris of the roof first. Then you add sodium hypochlorite with a surfactant (DO NOT USE DISH SOAP unless you want to create a nasty poison gas, read the instructions on your detergent to see if it is safe to mix with bleach, many are not)
Doing it this way reduces the amount of bleach you need. Get your bleach from a pool supply company, it’s cheaper and stronger.
Do not believe the myth that bleach will not kill your plants, the only time it doesn’t is if it is so dilute as to be almost pure water. How do you think the bleach can kill off moss and algae on the roof but not kill your garden plants?
That is exactly the wrong order of cleaning.
You should do the first pass with water to get as much dirt and debris of the roof first. Then you add sodium hypochlorite with a surfactant (DO NOT USE DISH SOAP unless you want to create a nasty poison gas, read the instructions on your detergent to see if it is safe to mix with bleach, many are not)
Doing it this way reduces the amount of bleach you need. Get your bleach from a pool supply company, it’s cheaper and stronger.
Do not believe the myth that bleach will not kill your plants, the only time it doesn’t is if it is so dilute as to be almost pure water. How do you think the bleach can kill off moss and algae on the roof but not kill your garden plants?
So twice as much walking around on the roof? yes?
That is exactly the wrong order of cleaning.
You should do the first pass with water to get as much dirt and debris of the roof first. Then you add sodium hypochlorite with a surfactant (DO NOT USE DISH SOAP unless you want to create a nasty poison gas, read the instructions on your detergent to see if it is safe to mix with bleach, many are not)
Doing it this way reduces the amount of bleach you need. Get your bleach from a pool supply company, it’s cheaper and stronger.
Do not believe the myth that bleach will not kill your plants, the only time it doesn’t is if it is so dilute as to be almost pure water. How do you think the bleach can kill off moss and algae on the roof but not kill your garden plants?
Bleach will try to oxidize and destroy everything it touches. Which is why its great at killing moss, mold and algae, because it penetrates the cell wall easily. Larger plants will take a beating and their cuticle helps protecting them from direct oxidising effects. Im not saying a really concentrated hypochlorite solution with a surfactant wont cause burns, but its easy to rinse the plant foilage with clean water when you done spraying the roof.
But always buy a sprayer without metal parts as chlorine will cause oxidation(rust),
Sodium hypochlorite is good for DIY´ers on the cheap, but the industry standard for cleaning dirty roofs is Benzalkonium chloride - Wikipedia
Which is unregulated and available to the public in Thailand on lazada.
So twice as much walking around on the roof? yes?
You should do the job to do a good job, if you spray the roof with sodium hypochlorite first you will use much more than is needed and there is no guarantee that it’s going to actually get to the roots, but if you want to go against the standard practice feel free to do it your way.
But always buy a sprayer without metal parts as chlorine will cause oxidation(rust),
All commercial sprayers use metal fittings even if you use downstream injection you can avoid most contact but there will be some so washing your equipment is good practice.
You can soft wash if you want but even then the spray tip is metal.
Sodium hypochlorite is good for DIY´ers on the cheap, but the industry standard for cleaning dirty roofs is Benzalkonium chloride - Wikipedia
If you actually read the studies you will find that it is far from proven safe a levels required for treatment and is long lasting.
However that is not true of sodium hyp ochlori te that has been studied in depth and very extensively due to its use in swimming pools and was first used in the 18th century.
sodium hyp ochlorite Is the prime chemical used in the USA not Benzalkonium chloride and their use dwarfs the European use case, so it’s only those who are restricted in their thinking who believe BK is superior to SH. They both have uses but SH has a rather longer pedigree.
Neither is safe if used carelessly.
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