[TomCrowther]

Hi, I'm hoping someone can help with this issue.
One of my customers has a large house with quite a lot of rendering. Main walls, sunken area leading to gym and pool area {quite damp as all below ground. The builder used thick slate type tiles for the tops of the walls and around the top. He used a dark coloured grout.
Long story short, all the grout lines result in dark staining down the render. Very unsightly. I have tried cleaning it a few times {softwashing with bleach followed by algo clear pro after  light scrubbing and powerwashing. The results after cleaning are quite poor to be honest, just lightens the marking from black to light brown. Customer has had the walls re-painted but of course it doesn't solve the problem.
Poor chap is suffering from cancer at the moment, house is up for sale and I want to try and fix this for him. Is there something I can use to seal the grout lines and prevent the colour from escaping. ? Thanks in advance for any suggestions.

[Smudger]

Anything bleach based or soft washing is only good for organic cleaning, it won't ( as you found out  ) touch this type of staining

depending on the paint that has now been applied you need something more acid based

I would go with a quality brick cleaning chemical - I used Tensid - but you will have to test now due to the paint- this combined with steam should give you th result your after

Darran

[Kev Martin]

Hi, I'm hoping someone can help with this issue.
One of my customers has a large house with quite a lot of rendering. Main walls, sunken area leading to gym and pool area {quite damp as all below ground. The builder used thick slate type tiles for the tops of the walls and around the top. He used a dark coloured grout.
Long story short, all the grout lines result in dark staining down the render. Very unsightly. I have tried cleaning it a few times {softwashing with bleach followed by algo clear pro after  light scrubbing and powerwashing. The results after cleaning are quite poor to be honest, just lightens the marking from black to light brown. Customer has had the walls re-painted but of course it doesn't solve the problem.
Poor chap is suffering from cancer at the moment, house is up for sale and I want to try and fix this for him. Is there something I can use to seal the grout lines and prevent the colour from escaping. ? Thanks in advance for any suggestions.

Post some good photos and I will help you

[TomCrowther]

Thanks Darran but I don't have hot/steam.
Kev, I tried to upload a couple of pics but they are all to large. Will try and shrink them.

[TomCrowther]

This is after cleaning Kev

[TomCrowther]

correction. This is an after photo

[Kev Martin]

The issue is that the cause really needs eradicating and the cause is primarily the bad design choices made.  They seem to have a combination of Algae and Efflorescence issues.  However, as you just want to solve it, I suggest using SRP Grout Colourant this will waterproof the grout lines with an epoxy covering to a colour that suits.

Kevin

[TomCrowther]

Cheers Kevin. I will give that a go.
Many thanks