Cellar plaster white patches

[Homestead101]

We’re having our cellar tanked and plastered and we’ve noticed some weird dotting in the plaster. It looks like salt is coming through too near the vents. The vents go directly to the outside wall and we’re worried it’s letting in water. We were told to get ventilation but it’s literally two giant holes through the wall. Any ideas before we cry?
It was taken back to brick, slurry, cement then plastered. At a complete loss

 

[ree]

OP,
I'm sorry to hear of your troubles.

Whats seems to be happening is damp is penetrating what you call tanking.
What you describe is not tanking. Tanking is a far more extensive treatment.
You say "slurry, cement then plastered" - what does cement mean?
What does plastered mean?
I can see gypsum skim finish has been used - thats wrong: no gypsum of any sort should be used in a damp situation.

Can you stand back and show far more context of the cellar? And a pic of the outside showing the air bricks or vent covers?
Is the cellar one room - does it have a window?

 

[Homestead101]

Hi, thank you for getting back to me. So my understanding is a tanking slurry was used, it was similar to K Slurry, then cement put over and then plastered. It’s only been done a week can damp show that quickly? What would you suggest the best course of action is please? I will take a better photo and post it. Yes it does have a window

 

[ree]

OP,
Its difficult to help you unless you answer all my questions? Such as, what exactly was the mix for "cement" and "plastered"? Cement means nothing by itself & what was it plastered with?

 

[^woody^]

Did you have the work done by a professional tanking firm, or a a random builder?

Is it a system, or with proprietary damp proofing products, or just done as you've described with ordinary cement and plaster?

Was the wall nuturalised first to deal with salts?