Damp patches on walls

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ajs123

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• 19 Mar 2021

• #1

I have these patches on my walls. I've sealed the outside render, 2 coats of bullseye 123, 2 coats of masonry paint outside, same on inside walls with emulsion not masonry paint, yet the patches are still coming through.
It is on a front facing wall, which are 3ft thick built in 1900s, doesn't occur in any other part if the house.
Can anyone please give me an idea of what's causing this? (New sealant on downstairs windows, but not upstairs ones yet, windows 2 yrs old).
Thank you.

 

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KenGMac

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• 19 Mar 2021

• #2

Suggest a very careful inspection of window seas between window and walls.

That is a first port of call.

Ken.

 

Wayners

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• 19 Mar 2021

• #3

Cavity tray problem maybe. This explains.

 

KenGMac

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• 19 Mar 2021

• #4

Wayners said:

Cavity tray problem maybe. This explains.

Click to expand...

Do not think they had Cavity Trays in "3 foot thick" walls built in the 1900s ?

 

Wayners

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• 19 Mar 2021

• #5

No. They didn't.. Oops.. Just going through posts quickly and not reading properly.
Sorry...


In that case you got troubles from above.
I've fixed windows with foam and new silicone but when water appears to the side like in photo it could be water getting in higher up or coming through the bricks.

 

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Bullet-Proof_Biscuit

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• 20 Mar 2021

• #6

I think the problem is you've just thoroughly sealed what were breathable walls.. Just think how is the moisture supposed to escape now other than the only porous side which is internal? Presumably there is no DPC and honstly 'sealing masonry' never does that, there will always be voids and cracks where rain/moisture can enter, this is fine originally because the porous lime mortar allowed an evaporation and drying route from the walls.

Furthermore noting those patches are fairly high, I would be looking at the first floor walls / window openings as the source if they appear following rain.