Stain on newly rendered wall

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rustykettle

New Member
Last summer I had a new front wall built which was breeze block, rendered with a Johnstone's coloured acrylic render. A few weeks after the render the stain shown in the photos below started to appear. I have not been able to get rid of them, I tried a product called Wet'n'Forget but it didn't work despite the manufacturer's assurance that it would in time. I am reluctant to just paint over them as I fear they will reappear. I don't know what the cause is, could it be water getting in where the tiled surface meets the brick / render? Any suggestions or ideas on how to remove the stains would be most welcome.
 

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it is the dirt from tiles.

you will never be free of it. just maintain.

you could use a guard. which is a clear protective coat.

but to clean up give it a very quick wipe over with a power hose from distance. too close will remove the render
 
Try a nylon brush a power washer at distance with some sugar soap Or fungicidal remover left overnight Or warm soapy water with a power washer at distancethe dirt is only sat on the surface so it’s trail and error with it.
 
To prevent it you could use some transparent sticks all to form a drip On the edge of the coping or even grind a nick in it.
 
As above a soft jet wash same as the slabs or block paving on the floor and the wheelie bins too , needs a clean every year
 
Mix some household bleach with hot water. Soak and agitate with a soft brush and leave for half an hour. Then rinse.
 
As above, but also clean the tiles,especially the disc- cut edge, and seal them with stone oil. As Owls says, use some clear sticksall mastic to a) stop it running off the side and b) form a drip edge on the front.
 
Cilit Bang black mould remover
Spray on, brush in, leave for an hour, wash off
Rinse and repeat. (Will look instantly better but never disappear though)
Or get a huge glass dome fitted over your property to keep weather off
 
rustykettle said:
Don't suppose you have any idea what the right chemicals might be? I tried power washing and steam cleaning both to no effect, is bleach safe on acrylic do you think?(y)
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Sodium hypochlorite. But don’t go buying the strong stuff. Can be dangerous in the wrong hands.
Domestic bleach is about 5% hypo. 50/50 with water will make it 2.5% and should do light soiling. If it doesn’t work try stronger.
 
Crazy how much of this bad detail is about. Nice new render looks untidy in a few months. Painters are going to have some major work in the future.
 
The stains on your render are likely caused by moisture ingress, possibly where the tiled surface meets the brick. Ensure the area is properly sealed to prevent further water penetration. Try using a product designed for efflorescence to clean the stains, followed by applying a breathable, water-repellent sealant to protect the surface.
 
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