Red Stain on outside walls

[Acoustic]

Our house is about 30 years old and is constructed from white-painted rendered brick.  The whole of one end of the building is marked with a deep red stain  in the white paintwork and I have seen something similar on a couple of other houses too.  Does anyone

a) know what causes this?

b) know how to get rid of it? 

We want to repaint the outside but I would hate to think it might come back or even show through the new paint.

 

Thanks

[jono]

I had this problem- it may be due to grains of ironstone in the sand/cement render.

I brushed on a stabilising paint before applying masonary paint. This has lasted two years - it's just starting to show through again in places.

Jono

[Pads]

Do you have red roof tiles ? could a coulour be running from the roof?

[Callie]

We lived in married quarters in Devon where the houses had the same problem.  The MOD used bleach sprayed on with a pressure washer.  It solved the problem, though I can't say whether it was perùanent or not.

[Richard T]

I have exactly the same problem on a single storey house I bought recently in 87. The stain is on the east gable end and covers the bottom two thirds of the wall but is shaped as if the top of the stain follows the shape of the roof. It's a very shaded area and even on the brightest of days gets no sun due to overhanging trees - in fact the area immediately around the wall remains damp most of the time.

There is evidence that this wall was once heavily covered in ivy but appears to have been cleared a few years ago and as the shape of the stain seems to follow the shape that I believe the ivy grew my assumption is that it was caused by the ivy - but I'm by no means certain of that.

My plan is to simply paint over the stain and see what happens. Despite being a gable end it's a relatively easy wall to paint and not a huge problem if the stain bleeds through again in which case I guess I'll have to find some other solution - probably use some sort of stabilizing solution and then repaint.

Work on this is due to start in a few days so if anyone has a definitive solution I too would be pleased to hear.

Richard T

[Val_2]

Here in Brittany it is very common to see red staining on the white/cream crépi and is caused by Trentepholias which is a terrestial algae caused by the humidity of the region and is a micro organism present all over here. It is normally eradicated by a high pressure wash containing a bleach of some sort as the smell permeates your nostrils and the operators reckon it lasts about ten years before having to be redone. Perhaps this is the same micro organism and a friend along the road with a house less than five years old already has this staining down the western gable.

[ams]

We had the same, it is called champignons, we consulted this board and some kind person recommended a product called antimousse. Spray it on and you will be rid of the problem in about two weeks. Cost about €11. The product can be purchased in any hardware.

 

ams

[Richard T]

Can it just be painted over?

Richard T

[Acoustic]

Thanks for the info.  Anyone else with a similar problem might be interested to know antimousse is on offer in Brico Depot at the moment, just over €2 for a large container.  I'll report back if it deals with our staining.

[Albert the InfoGipsy]

[quote user="Richard T"]Can it just be painted over?

Richard T
[/quote]

I wouldn't recommend it. The algae would probably reappear pretty quickly, especially if the paint is water based.

[Catalpa]

[quote user="Val_2"]Here in Brittany it is very common to see red staining on the white/cream crépi and is caused by Trentepholias which is a terrestial algae caused by the humidity of the region and is a micro organism present all over here. [/quote]

Very useful info Val, thanks. I have begun to notice a faint reddish tinge to some of the (3 year old) enduit on our west gable - and of course, most of the bad weather comes from the west. We're at the bottom of the Cotentin, just inland from Avranches. Now I know what to do. [:D]

[Jonzjob]

We have the same on our West wall. The house was built in 82. I tried a test patch with javel and was later told that the javel would have a detremental effect on the crepi. A couple of weeks back I sprayed it with anit-mousse and it looks much better now...

If your house is rough crepied and you paint it then from what I have been told you will be repainting every few years, but using aiti-mousse will last longer and you just spray it on. If you get a decient presure spray with a   l   o   n   g  lance on it there isn't even a lot of need for a ladder. Our lance is about 9 foot long...

Spraying has to be a lot easier than painting and cheaper too.

[Nearly Retired (I am now)]

We have the same problem on a west facing rendered wall of an extension built around 1986. The staining gets worse after rain and virtually disappears when the wall dries out in the sun. I too thought it was due to some iron constituent of the sand used in the original render mix.

As an experiment I painted two postage stamp sized areas with two coats of cream masonry paint a couple of years ago. So far nothing has bled through the painted areas and I was on the point of planning to paint the whole wall soon.

But, if this antmousse stuff is cheap enough I might give it a go first.

[Acoustic]

I did a test patch on our red stain using the €2.90 tub of antimousse from BricoDepot and it has worked perfectly - pristine white!  Now waiting for a non rainy/windy day when I will be up a ladder with the pulverisatuer and deal with the rest of it.  Thanks for the advice.

[Charlotte3]

I work for a French painting and decorating company and at this time of year we have lots of "facades" to do.

"Champignons" means mould in French and the particulat red stuff you mentioned is commonplace.

We power wash with a karcher, apply antimousse, then two coats masonry paint.....all guaranteed to last for ten years.

 

Aly

 

[nemltd]

Hi Aly,

Great bit of information for me.

Do French decorators charge by the square meter, only so I can gauge the cost of the job you describe.

Our red stuff is mainly on our south elevation.

 

Tony[:)]

[Alan Zoff]

My problem proved to be more specific than the general tendency for the render to go red. I discovered that a flue had in the distant past been bolted to the outside wall. The metal anchors to which the flue's retaining straps had been bolted had been cut off just below the surface of the wall and rendered over. Eventally, the iron in them caused a rust stain to bleed from each one, forming a continuous dark red streak down the wall.

I chiselled out the render to expose the metalwork, cut the anchors back further (couldn't get them out completely - seem to be locked into the wall somehow) and painted them with anti-rust primer before rerendering and painting.

I removed the stain with the mild hydrochloric acid solution they sell in all the supermarkets. Makes a nice green, foamy fizz (I don't recommend inhaling the noxious, chlorine-smelling fumes) which I neutralised by spraying with water with hosepipe. Pays to confine the solution to the main stain as the acid seems to bring out the red naturally occurring in the render so it's easy to make the stain wider than when you started....

I think I may have sorted it for some years, if not permanently.