White Spots On New Plaster.

[charliegolf]

Anyone have an idea what's causing this? Can I go ahead and paint (been about a month). Ta.

This is in the same room. Both internal walls, btw.

 

[HERTS P&D]

Is it salt leaking out from the wall?

Also, you floor tiles contain asbestos.

Andy

 

[charliegolf]

Will it stop leaking/can it be stopped? I mean, was it a one-off part of the drying process? Ta.

 

[HERTS P&D]

I found this online:

"Sometimes you can get salt deposits on newly plastered walls. Brush it off and see if it comes back."

Andy

 

[^woody^]

Something on the wall or in the joints has been activated/ leeched out in the wetting and drying process.

The problem you may have it's that this contamination may be drawn out further due to the natural absorption of plaster. It may need surface treating with a barrier paint.

 

[charliegolf]

Thanks both.

 

[mrrusty]

It may need surface treating with a barrier paint.

I agree. I have had a little of this on a chimney breast where the bricks are salt-poisoned and the water in the new plaster has leached the salts from the wall. Once they migrate to the surface, they are hygroscopic and continue to draw moisture from the air to grow crystals. In my experience you can significantly mitigate (but not completely eliminate) by using a barrier paint to prevent room moisture getting to the salts. I have successfully used ronseal dampseal and then emulsioned over. It has been 98% successful.

Sand it lightly, seal and see what happens. Unfortunately if this doesn't work you will probably have to strip back to brick and start again with salt-resistant materials.

Of course, do also check to make sure there are no pipe leaks etc. in the vicinity

 

[opps]

I agree. I have had a little of this on a chimney breast where the bricks are salt-poisoned and the water in the new plaster has leached the salts from the wall. Once they migrate to the surface, they are hygroscopic and continue to draw moisture from the air to grow crystals. In my experience you can significantly mitigate (but not completely eliminate) by using a barrier paint to prevent room moisture getting to the salts. I have successfully used ronseal dampseal and then emulsioned over. It has been 98% successful.

Sand it lightly, seal and see what happens. Unfortunately if this doesn't work you will probably have to strip back to brick and start again with salt-resistant materials.

Of course, do also check to make sure there are no pipe leaks etc. in the vicinity

One of my clients has a similar problem. After I decorated the top room, water stains continued. It turns out that the old soot in the chimney is the root cause. He has been advised to hack away the plaster and use sand/cement.

 

[mrrusty]

It turns out that the old soot in the chimney is the root cause.

I think it's not so much the soot but a combination of soot and gases caused by burning coal combining with water, creating acids which then react with the compounds in building materials and create the salts which cause problems