# Red stain on external walls



## nigel27

The external walls of my house (built 2007) are finished with a "chalk" like product. All houses in the estate are finished the same, none are painted. Now a lot of the houses, including my own have started to get Red streaks along the walls. It is making the houses look unkept. Is there something that can be put on these walls to clear this? I have also noticed this happening to other houses across the city (Galway)


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## Petermack

nigel27 said:


> The external walls of my house (built 2007) are finished with a "chalk" like product. All houses in the estate are finished the same, none are painted. Now a lot of the houses, including my own have started to get Red streaks along the walls. It is making the houses look unkept. Is there something that can be put on these walls to clear this? I have also noticed this happening to other houses across the city (Galway)


 
Im not quite sure what the chalk like product is your walls are finished in, butyou can try sealing the walls with Polybond PVA to reduce the porosity of the walls.


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## gareth1214

soduim hypochlorite (bleach) applied with a garden sprayer will remove the red stain. The stain is a fungus that is very common on white finished walls. I buy the solution by the gallon in my local hardware store.


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## DGOBS

That sounds fantastic for the environment


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## Leo

Please edit the title of your thread to make it a little more meaningful.
Leo


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## ted

Hi Nigel27. Nothing wrong with your title imo. This is very common in the west of Ireland. Your house is prob finished with a coloured render like KRend. It is porous and susceptible to the red fungus you are experiencing. You'll also see it on unpainted plastered walls and unpainted roof barges. Gareth1214's solution will work. I've brushed in thick bleach diluted with water. It should turn orange immediately and then disappear. Then rince the wall down with a garden hose. I notice that it ends to affect south facing elevations more often. BTW if you have a coloured render do not pressure wash it as it pits the render.


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## Leo

ted said:


> Nothing wrong with your title imo.


 
Not since it was updated anyway!


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## corkgal

Its actually an algae


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## Mrs. Doyle

nigel27 said:


> The external walls of my house (built 2007) are finished with a "chalk" like product. All houses in the estate are finished the same, none are painted. Now a lot of the houses, including my own have started to get Red streaks along the walls. It is making the houses look unkept. Is there something that can be put on these walls to clear this? I have also noticed this happening to other houses across the city (Galway)



Hi,

I don't want to scare you but it might be a good idea for you to get an expert to check out the problem as we had horrific problems many moons ago with the outside of our house and we wasted money trying out different things before we got an expert to look at it and then got it sorted.

All the houses in our estate have at one time or another suffered from what looked like green stains with mould effect.  Most of them have only had this problem recently whereas we were one of the first to notice it.

We put a recommended coating on it which cost quite a lot at the time and were told that it would last a lifetime.  When snow stuck to it it came away from the wall and we were back where we started.  

We got a guy out from at that time the Institute of Industrial Research and Standards and when he looked at it through a magnifying glass he said it was a mould type growth that had taken place because the builder painted the house while the plaster was still wet.

The only way to overcome it was to put up scaffolding, remove the bad paint with a high pressure water cleaner and then wash the bare walls with a chemical to kill the growth.

We then started afresh and put on pebble dash which is still there now.  It may have been an exaggeration but we were told at that time that if we did not get it back to basics the pebble dash may well have fallen off because the mould was so strong.

Your problem may well be something different but best to get it looked at by an expert.

A phone call to the Customer Service Depts. in some of the paint companies might guide you in the right direction.

Hope you get it sorted.


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## Cleaner

Great information guys.  Once I have got rid of the Red stain how to I prevent it from returning


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## amh

My parent's house gets this type of staining on a regular basis and as posted by others bleach is very effective in removing said stain. We just spray it on on leave it to kill it off. We just redo it as required. We notice it worst on the side of the house which is closest to those evergreen hedges that are everywhere. Don't know if it's just a coincidence or not.

It's not a big operation in our experience but it does look better when it's done alright. Good luck


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## blacktalons

there is a product called "mosgo" available in all hardware shops, and woodies and atlantic homecare etc. it is excellent for getting red of the red stain you get on walls etc. brush or spray it on,do NOT get it on glass as will not come off. bleach mixed with water may also work, wear eye protection when doing this job!!! Moss Algea and Lichen Control,made by Hygeia.


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