Efflorescence

jollyjack
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Efflorescence

Post by jollyjack » Thu Mar 07, 2019 6:58 pm

There is a corner of my WC, down at the ground, where (saltpetre?) salts leach from the wall, pushing off the paint. Strangely, it's a corner between an outer wall (limestone chunks) and an internal wall (parpaing). Which makes me think it might be what was used to decorate the internal surface - a mixture of lime and dirty sand?

Whatever, is there ANYTHING I can do to seal it, so I can paint it?

Or, do I have to hack it off, and replaster? This is not a big problem, but the surface is textured (well, most of it, now)

Cheers

chrisell
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Re: Efflorescence

Post by chrisell » Thu Mar 07, 2019 8:01 pm

Probably depends on its state and cause - I thought salts were mainly a function of damp. If its still damp - then its probably working out if its condensation or proper damp - but I had salts leaching out of UK plaster for a few months after the damp problem was fixed so it can be historical.

If its condensation that's just ventilation or warmth - obviously proper damp means find the cause first.

Assuming there is no ongoing damp and its just damp staining/salts- Stain Blocks/Sealers usually fix it - several coats then emulsion over - BUT if its walls needing to breathe causing a damp problem or a more deep seated problem all Stain Block does is push the visible problem elsewhere - the wall will not breathe post Stain Block so the water just rises/spreads - same with a proper damp problem - the stain block just hides the problem until it reappears around the stain block

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Nifty
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Re: Efflorescence

Post by Nifty » Thu Mar 07, 2019 8:45 pm

It might be possible to stop the moisture in the ground from rising by impregnating the wall at a low level with some product via holes drilled at regular intervals in the wall.

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Tom
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Re: Efflorescence

Post by Tom » Thu Mar 07, 2019 9:15 pm

https://www.nitterhousemasonry.com/tips ... orescence/

The cause of efflorescence is simple... the cure for this salting can be quite complicated. The above link gives a good overview.
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DominicBest
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Re: Efflorescence

Post by DominicBest » Thu Mar 07, 2019 10:40 pm

I presume that you’re talking about an old stone building. Is the stone wall covered with anything?

jollyjack
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Re: Efflorescence

Post by jollyjack » Fri Mar 08, 2019 11:38 am

Thanks, all.

@ Chrisell - not sure if it's damp. The WC is at house level, with the old fosse (empty and disused) underneath it. The old limestone wall is an outside wall, while the other side of the parpaing wall is a garage - earth floor, but 2 feet lower. I read somewhere that damp in a wall can only rise a metre or so, which roughly coincides with this problem. I don't think it's condensation - there's a ventilation fan, that runs on for 5 minures or so, after use.

@Nifty - I don't want to go that far, if I can avoid it

@Tom - thanks, I'll read that later

@Dominic - the inside is covered in whateer, the outside is covered in whatever it is that's used on all french housed. Not cement though - lime based.

Cheers

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Annabelle's Papa
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Re: Efflorescence

Post by Annabelle's Papa » Fri Mar 08, 2019 12:08 pm

It does sound like rising damp.

Is it possible to hack off some of the render so the wall can breathe, or maybe put a vent from the outside to the toilet.

As said, covering it or treating it will only move the problem on.
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Re: Efflorescence

Post by Mike » Sat Mar 09, 2019 11:49 am

The only way to tackle this type of problem is to lower the water table adjacent to the wall.

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Re: Efflorescence

Post by chrisell » Sat Mar 09, 2019 12:33 pm

I'd probably pull the plaster off in the affected area and see whats underneath - its really hard to guess from a distance - sometimes the cause is obvious once you pull plaster off - if the bricks/limestone are properly damp then you know. Bad join between wall and garage wall - water can get inside bad render/bad joints and become damp.

Air bricks near ground level - outer ground sloping towards the house - cement paths puddling - or a mix of all them - all can bring damp in some form.

But bottom corners of small loos - it can be as simple as cold/condensation - especially with outside wall/garage meeting.

You can play with a French drain - either done properly - or my dig a 45cm cm deep trench - spade width- and just fill with gravel - it does take water level down although its not the most professional method of putting a French drain in.

Rising damp is quite often blamed - but in my experience damp is usually a cock up somewhere - had it behind poor render - cement paths puddling next to a wall - cement paths higher than air bricks - and my personal favourite (house survey said severe rising damp) a bloody tumble dryer venting out the wrong hole onto the wall.

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Re: Efflorescence

Post by alittlebitmorefrench » Sat Mar 09, 2019 12:40 pm

Mike wrote:
Sat Mar 09, 2019 11:49 am
The only way to tackle this type of problem is to lower the water table adjacent to the wall.
or not.

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